IR: handle control flow constructs (#186)

* IR: handle control flow constructs

This change includes a bunch of fixes and additions to the IR path:

- `slang-ir-assembly` is now a valid output target (so we can use it for testing)
  - This uses what used to be the IR "dumping" logic, revamped to support much prettier output.
  - A future change will need to add back support for less prettified output to use when actually debugging

- IR generation for `for` loops and `if` statements is supported

- HLSL output from the above control flow constructs is implemented

- Revamped the handling of l-values, and in particular work on compound ops like `+=`

- Add basic IR support for `groupshared` variables

- Add basic IR support for storing compute thread-group size

- Output semantics on entry point parameters
  - This uses the AST structures to find semantics, so its still needs work

- Pass through loop unroll flags
  - This is required to match `fxc` output, at least until we implement
    unrolling ourselves.

* Fixup: 64-bit build issues.

* fixup for merge

17 files changed, 2767 insertions, 609 deletions

diff --git a/source/core/slang-string.cpp b/source/core/slang-string.cpp
index 9bc9e3a54..5a3d8e4f9 100644
--- a/source/core/slang-string.cpp
+++ b/source/core/slang-string.cpp
@@ -266,7 +266,7 @@ namespace Slang
         append(slice.begin(), slice.end());
     }
 
-    void String::append(int value, int radix)
+    void String::append(int32_t value, int radix)
     {
         enum { kCount = 33 };
         char* data = prepareForAppend(kCount);
@@ -275,7 +275,7 @@ namespace Slang
         buffer->length += count;
     }
 
-    void String::append(unsigned int value, int radix)
+    void String::append(uint32_t value, int radix)
     {
         enum { kCount = 33 };
         char* data = prepareForAppend(kCount);
@@ -284,7 +284,7 @@ namespace Slang
         buffer->length += count;
     }
 
-    void String::append(long long value, int radix)
+    void String::append(int64_t value, int radix)
     {
         enum { kCount = 65 };
         char* data = prepareForAppend(kCount);
@@ -293,6 +293,14 @@ namespace Slang
         buffer->length += count;
     }
 
+    void String::append(uint64_t value, int radix)
+    {
+        enum { kCount = 65 };
+        char* data = prepareForAppend(kCount);
+        auto count = IntToAscii(data, value, radix);
+        ReverseInternalAscii(data, count);
+        buffer->length += count;
+    }
 
     void String::append(float val, const char * format)
     {
diff --git a/source/core/slang-string.h b/source/core/slang-string.h
index 98fd51a07..ed333f8e8 100644
--- a/source/core/slang-string.h
+++ b/source/core/slang-string.h
@@ -257,9 +257,10 @@ namespace Slang
 			return getData() + getLength();
 		}
 
-        void append(int value, int radix = 10);
-        void append(unsigned int value, int radix = 10);
-        void append(long long value, int radix = 10);
+        void append(int32_t value, int radix = 10);
+        void append(uint32_t value, int radix = 10);
+        void append(int64_t value, int radix = 10);
+        void append(uint64_t value, int radix = 10);
         void append(float val, const char * format = "%g");
         void append(double val, const char * format = "%g");
 
diff --git a/source/slang/compiler.cpp b/source/slang/compiler.cpp
index 9ca1d247f..25ae460c7 100644
--- a/source/slang/compiler.cpp
+++ b/source/slang/compiler.cpp
@@ -499,25 +499,14 @@ namespace Slang
     }
 #endif
 
-#if 0
-    String emitSPIRVAssembly(
-        ExtraContext&				context)
+    List<uint8_t> emitSlangIRForEntryPoint(
+        EntryPointRequest*  entryPoint)
     {
-        if(context.getTranslationUnitOptions().entryPoints.Count() == 0)
-        {
-            // TODO(tfoley): need to write diagnostics into this whole thing...
-            fprintf(stderr, "no entry point specified\n");
-            return "";
-        }
-
-        StringBuilder sb;
-        for (auto entryPoint : context.getTranslationUnitOptions().entryPoints)
-        {
-            sb << emitSPIRVAssemblyForEntryPoint(context, entryPoint);
-        }
-        return sb.ProduceString();
+        SLANG_UNIMPLEMENTED_X("Slang IR Binary Generation");
     }
-#endif
+
+    String emitSlangIRAssemblyForEntryPoint(
+        EntryPointRequest*  entryPoint);
 
     // Do emit logic for a single entry point
     CompileResult emitEntryPoint(
@@ -578,6 +567,22 @@ namespace Slang
             }
             break;
 
+        case CodeGenTarget::SlangIR:
+            {
+                List<uint8_t> code = emitSlangIRForEntryPoint(entryPoint);
+                maybeDumpIntermediate(compileRequest, code.Buffer(), code.Count(), target);
+                result = CompileResult(code);
+            }
+            break;
+
+        case CodeGenTarget::SlangIRAssembly:
+            {
+                String code = emitSlangIRAssemblyForEntryPoint(entryPoint);
+                maybeDumpIntermediate(compileRequest, code.Buffer(), target);
+                result = CompileResult(code);
+            }
+            break;
+
         case CodeGenTarget::None:
             // The user requested no output
             break;
@@ -957,6 +962,10 @@ namespace Slang
             dumpIntermediateText(compileRequest, data, size, ".dxbc.asm");
             break;
 
+        case CodeGenTarget::SlangIRAssembly:
+            dumpIntermediateText(compileRequest, data, size, ".slang-ir.asm");
+            break;
+
         case CodeGenTarget::SPIRV:
             dumpIntermediateBinary(compileRequest, data, size, ".spv");
             {
@@ -972,6 +981,15 @@ namespace Slang
                 dumpIntermediateText(compileRequest, dxbcAssembly.begin(), dxbcAssembly.Length(), ".dxbc.asm");
             }
             break;
+
+        case CodeGenTarget::SlangIR:
+            dumpIntermediateBinary(compileRequest, data, size, ".slang-ir");
+            {
+                // TODO: need to support dissassembly from Slang IR binary
+//                String slangIRAssembly = dissassembleSlangIR(compileRequest, data, size);
+//                dumpIntermediateText(compileRequest, slangIRAssembly.begin(), slangIRAssembly.Length(), ".slang-ir.asm");
+            }
+            break;
         }
     }
 
diff --git a/source/slang/compiler.h b/source/slang/compiler.h
index b6eca1b36..7ec812d63 100644
--- a/source/slang/compiler.h
+++ b/source/slang/compiler.h
@@ -47,6 +47,8 @@ namespace Slang
         DXBytecode          = SLANG_DXBC,
         DXBytecodeAssembly  = SLANG_DXBC_ASM,
         ReflectionJSON      = SLANG_REFLECTION_JSON,
+        SlangIR             = SLANG_IR,
+        SlangIRAssembly     = SLANG_IR_ASM,
     };
 
     enum class LineDirectiveMode : SlangLineDirectiveMode
diff --git a/source/slang/emit.cpp b/source/slang/emit.cpp
index 209436da4..25a0b5323 100644
--- a/source/slang/emit.cpp
+++ b/source/slang/emit.cpp
@@ -1,6 +1,7 @@
 // emit.cpp
 #include "emit.h"
 
+#include "ir-insts.h"
 #include "lower.h"
 #include "lower-to-ir.h"
 #include "name.h"
@@ -3966,11 +3967,16 @@ emitDeclImpl(decl, nullptr);
         {
             Simple,
             Ptr,
+            Array,
         };
 
         Flavor flavor;
         IRDeclaratorInfo*   next;
-        String const* name;
+        union
+        {
+            String const* name;
+            IRInst* elementCount;
+        };
     };
 
     void emitDeclarator(
@@ -3991,6 +3997,13 @@ emitDeclImpl(decl, nullptr);
             emit("*");
             emitDeclarator(context, declarator->next);
             break;
+
+        case IRDeclaratorInfo::Flavor::Array:
+            emitDeclarator(context, declarator->next);
+            emit("[");
+            emitIROperand(context, declarator->elementCount);
+            emit("]");
+            break;
         }
     }
 
@@ -4008,6 +4021,13 @@ emitDeclImpl(decl, nullptr);
             emit(((IRConstant*) inst)->u.floatVal);
             break;
 
+        case kIROp_boolConst:
+            {
+                bool val = ((IRConstant*)inst)->u.intVal != 0;
+                emit(val ? "true" : "false");
+            }
+            break;
+
         default:
             SLANG_UNIMPLEMENTED_X("val case for emit");
             break;
@@ -4028,6 +4048,8 @@ emitDeclImpl(decl, nullptr);
         CASE(Float32Type,   float);
         CASE(Int32Type,     int);
         CASE(UInt32Type,    uint);
+        CASE(VoidType,      void);
+        CASE(BoolType,      bool);
 
     #undef CASE
 
@@ -4084,6 +4106,15 @@ emitDeclImpl(decl, nullptr);
             }
             break;
 
+        case kIROp_structuredBufferType:
+            {
+                auto tt = (IRBufferType*) type;
+                emit("StructuredBuffer<");
+                emitIRType(context, tt->getElementType(), nullptr);
+                emit(">");
+            }
+            break;
+
         case kIROp_SamplerType:
             {
                 // TODO: actually look at the flavor and emit the right name
@@ -4127,11 +4158,11 @@ emitDeclImpl(decl, nullptr);
         IRType*             type,
         IRDeclaratorInfo*   declarator)
     {
-        switch( type->op )
+        switch (type->op)
         {
         case kIROp_PtrType:
             {
-                auto ptrType = (IRPtrType*) type;
+                auto ptrType = (IRPtrType*)type;
 
                 IRDeclaratorInfo ptrDeclarator;
                 ptrDeclarator.flavor = IRDeclaratorInfo::Flavor::Ptr;
@@ -4140,6 +4171,18 @@ emitDeclImpl(decl, nullptr);
             }
             break;
 
+        case kIROp_arrayType:
+            {
+                auto arrayType = (IRArrayType*)type;
+
+                IRDeclaratorInfo arrayDeclarator;
+                arrayDeclarator.flavor = IRDeclaratorInfo::Flavor::Array;
+                arrayDeclarator.elementCount = arrayType->getElementCount();
+                arrayDeclarator.next = declarator;
+                emitIRType(context, arrayType->getElementType(), &arrayDeclarator);
+            }
+            break;
+
         default:
             emitIRSimpleType(context, type);
             emitDeclarator(context, declarator);
@@ -4178,6 +4221,7 @@ emitDeclImpl(decl, nullptr);
 
         case kIROp_IntLit:
         case kIROp_FloatLit:
+        case kIROp_boolConst:
         case kIROp_FieldAddress:
         case kIROp_getElementPtr:
             return true;
@@ -4280,17 +4324,9 @@ emitDeclImpl(decl, nullptr);
         switch(inst->op)
         {
         case kIROp_IntLit:
-            {
-                auto irConst = (IRConstant*) inst;
-                emit(irConst->u.intVal);
-            }
-            break;
-
         case kIROp_FloatLit:
-            {
-                auto irConst = (IRConstant*) inst;
-                emit(irConst->u.floatVal);
-            }
+        case kIROp_boolConst:
+            emitIRSimpleValue(context, inst);
             break;
 
         case kIROp_Construct:
@@ -4351,8 +4387,39 @@ emitDeclImpl(decl, nullptr);
         CASE(kIROp_Div, /);
         CASE(kIROp_Mod, %);
 
+        CASE(kIROp_Lsh, <<);
+        CASE(kIROp_Rsh, >>);
+
+        CASE(kIROp_Eql, ==);
+        CASE(kIROp_Neq, !=);
+        CASE(kIROp_Greater, >);
+        CASE(kIROp_Less, <);
+        CASE(kIROp_Geq, >=);
+        CASE(kIROp_Leq, <=);
+
+        CASE(kIROp_BitAnd, &);
+        CASE(kIROp_BitXor, ^);
+        CASE(kIROp_BitOr, |);
+
+        CASE(kIROp_And, &&);
+        CASE(kIROp_Or, ||);
+
 #undef CASE
 
+        case kIROp_Not:
+            {
+                if (inst->getType()->op == kIROp_BoolType)
+                {
+                    emit("!");
+                }
+                else
+                {
+                    emit("~");
+                }
+                emitIROperand(context, inst->getArg(1));
+            }
+            break;
+
         case kIROp_Sample:
             emitIROperand(context, inst->getArg(1));
             emit(".Sample(");
@@ -4408,6 +4475,18 @@ emitDeclImpl(decl, nullptr);
             emit("]");
             break;
 
+        case kIROp_BufferStore:
+            emitIROperand(context, inst->getArg(1));
+            emit("[");
+            emitIROperand(context, inst->getArg(2));
+            emit("] = ");
+            emitIROperand(context, inst->getArg(3));
+            break;
+
+        case kIROp_GroupMemoryBarrierWithGroupSync:
+            emit("GroupMemoryBarrierWithGroupSync()");
+            break;
+
         case kIROp_getElement:
         case kIROp_getElementPtr:
             emitIROperand(context, inst->getArg(1));
@@ -4426,8 +4505,29 @@ emitDeclImpl(decl, nullptr);
             emit(")");
             break;
 
+        case kIROp_swizzle:
+            {
+                auto ii = (IRSwizzle*)inst;
+                emitIROperand(context, ii->getBase());
+                emit(".");
+                UInt elementCount = ii->getElementCount();
+                for (UInt ee = 0; ee < elementCount; ++ee)
+                {
+                    IRInst* irElementIndex = ii->getElementIndex(ee);
+                    assert(irElementIndex->op == kIROp_IntLit);
+                    IRConstant* irConst = (IRConstant*)irElementIndex;
+
+                    UInt elementIndex = (UInt)irConst->u.intVal;
+                    assert(elementIndex < 4);
+
+                    char const* kComponents[] = { "x", "y", "z", "w" };
+                    emit(kComponents[elementIndex]);
+                }
+            }
+            break;
+
         default:
-            emit("/* uhandled */");
+            emit("/* unhandled */");
             break;
         }
     }
@@ -4478,6 +4578,51 @@ emitDeclImpl(decl, nullptr);
             emitIROperand(context, ((IRReturnVal*) inst)->getVal());
             emit(";\n");
             break;
+
+        case kIROp_swizzleSet:
+            {
+                auto ii = (IRSwizzleSet*)inst;
+                emitIRInstResultDecl(context, inst);
+                emitIROperand(context, inst->getArg(1));
+                emit(";\n");
+                emitIROperand(context, inst);
+                emit(".");
+                UInt elementCount = ii->getElementCount();
+                for (UInt ee = 0; ee < elementCount; ++ee)
+                {
+                    IRInst* irElementIndex = ii->getElementIndex(ee);
+                    assert(irElementIndex->op == kIROp_IntLit);
+                    IRConstant* irConst = (IRConstant*)irElementIndex;
+
+                    UInt elementIndex = (UInt)irConst->u.intVal;
+                    assert(elementIndex < 4);
+
+                    char const* kComponents[] = { "x", "y", "z", "w" };
+                    emit(kComponents[elementIndex]);
+                }
+                emit(" = ");
+                emitIROperand(context, inst->getArg(2));
+                emit(";\n");
+            }
+            break;
+
+#if 0
+        case kIROp_unconditionalBranch:
+            emit("// unconditionalBranch ");
+            emitIROperand(context, inst->getArg(1));
+            emit("\n");
+            break;
+
+        case kIROp_conditionalBranch:
+            emit("// conditionalBranch ");
+            emitIROperand(context, inst->getArg(1));
+            emit(" ");
+            emitIROperand(context, inst->getArg(2));
+            emit(" ");
+            emitIROperand(context, inst->getArg(3));
+            emit("\n");
+            break;
+#endif
         }
     }
 
@@ -4515,6 +4660,238 @@ emitDeclImpl(decl, nullptr);
         }
     }
 
+    // We want to emit a range of code in the IR, represented
+    // by the blocks that are logically in the interval [begin, end)
+    // which we consider as a single-entry multiple-exit region.
+    //
+    // Note: because there are multiple exists, control flow
+    // may exit this region with operations that do *not* branch
+    // to `end`, but such non-local control flow will hopefully
+    // be captured.
+    // 
+    void emitIRStmtsForBlocks(
+        EmitContext*    context,
+        IRBlock*        begin,
+        IRBlock*        end)
+    {
+        IRBlock* block = begin;
+        while(block != end)
+        {
+            // Start by emitting the non-terminator instructions in the block.
+            auto terminator = block->lastChild;
+            assert(isTerminatorInst(terminator));
+            for (auto inst = block->firstChild; inst != terminator; inst = inst->nextInst)
+            {
+                emitIRInst(context, inst);
+            }
+
+            // Now look at the terminator instruction, which will tell us what we need to emit next.
+
+            switch (terminator->op)
+            {
+            default:
+                SLANG_UNEXPECTED("terminator inst");
+                return;
+
+            case kIROp_ReturnVal:
+            case kIROp_ReturnVoid:
+                emitIRInst(context, terminator);
+                return;
+
+            case kIROp_if:
+                {
+                    // One-sided `if` statement
+                    auto t = (IRIf*)terminator;
+
+                    auto trueBlock = t->getTrueBlock();
+                    auto afterBlock = t->getAfterBlock();
+
+                    emit("if(");
+                    emitIROperand(context, t->getCondition());
+                    emit(")\n{\n");
+                    emitIRStmtsForBlocks(
+                        context,
+                        trueBlock,
+                        afterBlock);
+                    emit("}\n");
+
+                    // Continue with the block after the `if`
+                    block = afterBlock;
+                }
+                break;
+
+            case kIROp_ifElse:
+                {
+                    // Two-sided `if` statement
+                    auto t = (IRIfElse*)terminator;
+
+                    auto trueBlock = t->getTrueBlock();
+                    auto falseBlock = t->getFalseBlock();
+                    auto afterBlock = t->getAfterBlock();
+
+                    emit("if(");
+                    emitIROperand(context, t->getCondition());
+                    emit(")\n{\n");
+                    emitIRStmtsForBlocks(
+                        context,
+                        trueBlock,
+                        afterBlock);
+                    emit("}\nelse\n{\n");
+                    emitIRStmtsForBlocks(
+                        context,
+                        falseBlock,
+                        afterBlock);
+                    emit("}\n");
+
+                    // Continue with the block after the `if`
+                    block = afterBlock;
+                }
+                break;
+
+            case kIROp_loop:
+                {
+                    // Header for a `while` or `for` loop
+                    auto t = (IRLoop*)terminator;
+
+                    auto targetBlock = t->getTargetBlock();
+                    auto breakBlock = t->getBreakBlock();
+                    auto continueBlock = t->getContinueBlock();
+
+                    if (auto loopControlDecoration = t->findDecoration<IRLoopControlDecoration>())
+                    {
+                        switch (loopControlDecoration->mode)
+                        {
+                        case kIRLoopControl_Unroll:
+                            emit("[unroll]\n");
+                            break;
+
+                        default:
+                            break;
+                        }
+                    }
+
+                    // The challenging case for a loop is when
+                    // there is a `continue` block that we
+                    // need to deal with.
+                    //
+                    if (continueBlock == targetBlock)
+                    {
+                        // There is no continue block, so
+                        // we only need to emit an endless
+                        // loop and then manually `break`
+                        // out of it in the right place(s)
+                        emit("for(;;)\n{\n");
+
+                        emitIRStmtsForBlocks(
+                            context,
+                            targetBlock,
+                            nullptr);
+
+                        emit("}\n");
+                    }
+                    else
+                    {
+                        // Okay, we've got a `continue` block,
+                        // which means we really want to emit
+                        // something akin to:
+                        //
+                        //     for(;; <continueBlock>) { <bodyBlock> }
+                        //
+                        // In principle this isn't so bad, since the
+                        // first case is just interVal [`continueBlock`, `targetBlock`)
+                        // and the latter is the interval [`targetBlock`, `continueBlock`).
+                        //
+                        // The challenge of course is that a `for` statement
+                        // only supports *expressions* in the continue part,
+                        // and we might have expanded things into multiple
+                        // instructions (especially if we inlined or desugared anything).
+                        //
+                        // There are a variety of ways we can support lowering this,
+                        // but for now we are going to do something expedient
+                        // that mimics what `fxc` seems to do:
+                        //
+                        // - Output loop body as `for(;;) { <bodyBlock> <continueBlock> }`
+                        // - At any `continue` site, output `{ <continueBlock>; continue; }`
+                        //
+                        // This isn't ideal because it leads to code duplication, but
+                        // it matches what `fxc` does so hopefully it will be the
+                        // best option for our tests.
+                        //
+
+                        emit("for(;;)\n{\n");
+
+                        // TODO: Okay, we *said* we'd do this special
+                        // handling of the `continue` sites, but
+                        // we aren't actually setting anything up here...
+                        //
+
+                        emitIRStmtsForBlocks(
+                            context,
+                            targetBlock,
+                            nullptr);
+
+                        emit("}\n");
+
+                    }
+
+                    // Continue with the block after the loop
+                    block = breakBlock;
+                }
+                break;
+
+            case kIROp_break:
+                emit("break;\n");
+                return;
+
+            case kIROp_continue:
+                emit("continue;\n");
+                return;
+
+            case kIROp_loopTest:
+                {
+                    // Loop condition being tested
+                    auto t = (IRLoopTest*)terminator;
+
+                    auto afterBlock = t->getTrueBlock();
+
+                    emit("if(");
+                    emitIROperand(context, t->getCondition());
+                    emit(")\n{} else break;\n");
+
+                    // Continue with the block after the test
+                    block = afterBlock;
+                }
+                break;
+
+            case kIROp_unconditionalBranch:
+                {
+                    // Unconditional branch as part of normal
+                    // control flow. This is either a forward
+                    // edge to the "next" block in an ordinary
+                    // block, or a backward edge to the top
+                    // of a loop.
+                    auto t = (IRUnconditionalBranch*)terminator;
+                    block = t->getTargetBlock();
+                }
+                break;
+
+            case kIROp_conditionalBranch:
+                SLANG_UNEXPECTED("terminator inst");
+                return;
+            }
+
+            // If we reach this point, then we've emitted
+            // one block, and we have a new block where
+            // control flow continues.
+            //
+            // We need to handle a special case here,
+            // when control flow jumps back to the
+            // starting block of the range we were
+            // asked to work with:
+            if (block == begin) return;
+        }
+    }
+
     void emitIRFunc(
         EmitContext*    context,
         IRFunc*         func)
@@ -4522,6 +4899,19 @@ emitDeclImpl(decl, nullptr);
         auto funcType = func->getType();
         auto resultType = func->getResultType();
 
+        // Deal with decorations that need
+        // to be emitted as attributes
+        if (auto threadGroupSizeDecoration = func->findDecoration<IRComputeThreadGroupSizeDecoration>())
+        {
+            emit("[numthreads(");
+            for (int ii = 0; ii < 3; ++ii)
+            {
+                if (ii != 0) emit(", ");
+                Emit(threadGroupSizeDecoration->sizeAlongAxis[ii]);
+            }
+            emit(")]\n");
+        }
+
         auto name = getName(func);
 
         emitIRType(context, resultType, name);
@@ -4535,6 +4925,8 @@ emitDeclImpl(decl, nullptr);
 
             auto paramName = getName(pp);
             emitIRType(context, pp->getType(), paramName);
+
+            emitIRSemantics(context, pp);
         }
         emit(")");
 
@@ -4548,6 +4940,10 @@ emitDeclImpl(decl, nullptr);
             emit("\n{\n");
 
             // Need to emit the operations in the blocks of the function
+
+            emitIRStmtsForBlocks(context, func->getFirstBlock(), nullptr);
+
+#if 0
             for( auto bb = func->getFirstBlock(); bb; bb = bb->getNextBlock() )
             {
                 // TODO: need to handle control flow and so forth...
@@ -4556,6 +4952,7 @@ emitDeclImpl(decl, nullptr);
                     emitIRInst(context, ii);
                 }
             }
+#endif
 
             emit("}\n");
         }
@@ -4687,7 +5084,8 @@ emitDeclImpl(decl, nullptr);
         IRVar*          varDecl)
     {
         auto allocatedType = varDecl->getType();
-        auto varType = ((IRPtrType*) allocatedType)->getValueType();
+        auto varType = allocatedType->getValueType();
+        auto addressSpace = allocatedType->getAddressSpace();
 
         switch( varType->op )
         {
@@ -4706,6 +5104,16 @@ emitDeclImpl(decl, nullptr);
         
         emitIRVarModifiers(context, layout);
 
+        switch (addressSpace)
+        {
+        default:
+            break;
+
+        case kIRAddressSpace_GroupShared:
+            emit("groupshared ");
+            break;
+        }
+
         emitIRType(context, varType, getName(varDecl));
 
         emitIRSemantics(context, varDecl);
diff --git a/source/slang/hlsl.meta.slang b/source/slang/hlsl.meta.slang
index 7c7d3fda0..0ca838ff5 100644
--- a/source/slang/hlsl.meta.slang
+++ b/source/slang/hlsl.meta.slang
@@ -29,7 +29,13 @@ __magic_type(HLSLByteAddressBufferType) struct ByteAddressBuffer
     __intrinsic_op uint4 Load4(int location, out uint status);
 };
 
-__generic<T> __magic_type(HLSLStructuredBufferType) struct StructuredBuffer
+__generic<T>
+__magic_type(HLSLStructuredBufferType)
+__intrinsic_type(${{
+	// TODO: we really need a simple way to write an "expression splice"
+	sb << kIROp_structuredBufferType;
+}})
+struct StructuredBuffer
 {
     __intrinsic_op void GetDimensions(
         out uint numStructs,
diff --git a/source/slang/hlsl.meta.slang.cpp b/source/slang/hlsl.meta.slang.cpp
index a3744f620..49254ac60 100644
--- a/source/slang/hlsl.meta.slang.cpp
+++ b/source/slang/hlsl.meta.slang.cpp
@@ -29,7 +29,14 @@ sb << "    __intrinsic_op uint4 Load4(int location);\n";
 sb << "    __intrinsic_op uint4 Load4(int location, out uint status);\n";
 sb << "};\n";
 sb << "\n";
-sb << "__generic<T> __magic_type(HLSLStructuredBufferType) struct StructuredBuffer\n";
+sb << "__generic<T>\n";
+sb << "__magic_type(HLSLStructuredBufferType)\n";
+sb << "__intrinsic_type(";
+
+	// TODO: we really need a simple way to write an "expression splice"
+	sb << kIROp_structuredBufferType;
+sb << ")\n";
+sb << "struct StructuredBuffer\n";
 sb << "{\n";
 sb << "    __intrinsic_op void GetDimensions(\n";
 sb << "        out uint numStructs,\n";
diff --git a/source/slang/ir-inst-defs.h b/source/slang/ir-inst-defs.h
index dab7aa3d7..deaf02d56 100644
--- a/source/slang/ir-inst-defs.h
+++ b/source/slang/ir-inst-defs.h
@@ -13,24 +13,29 @@
 // Invalid operation: should not appear in valid code
 INST(Nop, nop, 0, 0)
 
-INST(TypeType,    type.type,      0, 0)
-INST(VoidType,    type.void,      0, 0)
-INST(BlockType,   type.block,     0, 0)
-INST(VectorType,  type.vector,    2, 0)
-INST(MatrixType,  matrixType,     3, 0)
-INST(BoolType,    type.bool,      0, 0)
-INST(Float32Type, type.f32,       0, 0)
-INST(Int32Type,   type.i32,       0, 0)
-INST(UInt32Type,  type.u32,       0, 0)
-INST(StructType,  type.struct,    0, PARENT)
-INST(FuncType, func_type, 0, 0)
-INST(PtrType, ptr_type, 1, 0)
-INST(TextureType, texture_type, 2, 0)
-INST(SamplerType, sampler_type, 1, 0)
-INST(ConstantBufferType, constant_buffer_type, 1, 0)
-INST(TextureBufferType, texture_buffer_type, 1, 0)
-INST(readWriteStructuredBufferType, readWriteStructuredBufferType, 1, 0)
-
+INST(TypeType, Type, 0, 0)
+INST(VoidType, Void, 0, 0)
+INST(BlockType, Block, 0, 0)
+INST(VectorType, Vec, 2, 0)
+INST(MatrixType, Mat, 3, 0)
+INST(arrayType, Array, 2, 0)
+
+INST(BoolType, Bool, 0, 0)
+INST(Float32Type, Float32, 0, 0)
+INST(Int32Type, Int32, 0, 0)
+INST(UInt32Type, UInt32, 0, 0)
+INST(StructType, Struct, 0, PARENT)
+INST(FuncType, Func, 0, 0)
+INST(PtrType, Ptr, 1, 0)
+INST(TextureType, Texture, 2, 0)
+INST(SamplerType, SamplerState, 1, 0)
+INST(ConstantBufferType, ConstantBuffer, 1, 0)
+INST(TextureBufferType, TextureBuffer, 1, 0)
+
+INST(structuredBufferType, StructuredBuffer, 1, 0)
+INST(readWriteStructuredBufferType, RWStructuredBuffer, 1, 0)
+
+INST(boolConst, boolConst, 0, 0)
 INST(IntLit, integer_constant, 0, 0)
 INST(FloatLit, float_constant, 0, 0)
 
@@ -57,9 +62,48 @@ INST(FieldAddress, get_field_addr, 2, 0)
 INST(getElement, getElement, 2, 0)
 INST(getElementPtr, getElementPtr, 2, 0)
 
+// A swizzle of a vector:
+//
+// %dst = swizzle %src %idx0 %idx1 ...
+//
+// where:
+// - `src` is a vector<T,N>
+// - `dst` is a vector<T,M>
+// - `idx0` through `idx[M-1]` are literal integers
+//
+INST(swizzle, swizzle, 1, 0)
+
+// Setting a vector via swizzle
+//
+// %dst = swizzle %base %src %idx0 %idx1 ...
+//
+// where:
+// - `base` is a vector<T,N>
+// - `dst` is a vector<T,N>
+// - `src` is a vector<T,M>
+// - `idx0` through `idx[M-1]` are literal integers
+//
+// The semantics of the op is:
+//
+//     dst = base;
+//     for(ii : 0 ... M-1 )
+//         dst[ii] = src[idx[ii]];
+//
+INST(swizzleSet, swizzleSet, 2, 0)
+
+
 INST(ReturnVal, return_val, 1, 0)
 INST(ReturnVoid, return_void, 1, 0)
 
+INST(unconditionalBranch, unconditionalBranch, 1, 0)
+INST(break, break, 1, 0)
+INST(continue, continue, 1, 0)
+INST(loop, loop, 3, 0)
+
+INST(conditionalBranch, conditionalBranch, 1, 0)
+INST(if, if, 3, 0)
+INST(ifElse, ifElse, 4, 0)
+INST(loopTest, loopTest, 3, 0)
 
 INST(Add, add, 2, 0)
 INST(Sub, sub, 2, 0)
@@ -139,6 +183,8 @@ INST(Sample, sample, 3, 0)
 
 INST(SampleGrad, sampleGrad, 4, 0)
 
+INST(GroupMemoryBarrierWithGroupSync, GroupMemoryBarrierWithGroupSync, 0, 0)
+
 PSEUDO_INST(Pos)
 PSEUDO_INST(PreInc)
 
diff --git a/source/slang/ir-insts.h b/source/slang/ir-insts.h
new file mode 100644
index 000000000..846e87bb6
--- /dev/null
+++ b/source/slang/ir-insts.h
@@ -0,0 +1,569 @@
+// ir-insts.h
+#ifndef SLANG_IR_INSTS_H_INCLUDED
+#define SLANG_IR_INSTS_H_INCLUDED
+
+// This file extends the core definitions in `ir.h`
+// with a wider variety of concrete instructions,
+// and a "builder" abstraction.
+//
+// TODO: the builder probably needs its own file.
+
+#include "compiler.h"
+#include "ir.h"
+
+namespace Slang {
+
+class Decl;
+
+// Associates an IR-level decoration with a source declaration
+// in the high-level AST, that can be used to extract
+// additional information that informs code emission.
+struct IRHighLevelDeclDecoration : IRDecoration
+{
+    enum { kDecorationOp = kIRDecorationOp_HighLevelDecl };
+
+    Decl* decl;
+};
+
+// Associates an IR-level decoration with a source layout
+struct IRLayoutDecoration : IRDecoration
+{
+    enum { kDecorationOp = kIRDecorationOp_Layout };
+
+    Layout* layout;
+};
+
+// Identifies a function as an entry point for some stage
+struct IREntryPointDecoration : IRDecoration
+{
+    enum { kDecorationOp = kIRDecorationOp_EntryPoint };
+
+    Profile profile;
+};
+
+// Associates a compute-shader entry point function
+// with a thread-group size.
+struct IRComputeThreadGroupSizeDecoration : IRDecoration
+{
+    enum { kDecorationOp = kIRDecorationOp_ComputeThreadGroupSize };
+
+    UInt sizeAlongAxis[3];
+};
+
+enum IRLoopControl
+{
+    kIRLoopControl_Unroll,
+};
+
+struct IRLoopControlDecoration : IRDecoration
+{
+    enum { kDecorationOp = kIRDecorationOp_LoopControl };
+
+    IRLoopControl mode;
+};
+
+// Types
+
+struct IRVectorType : IRType
+{
+    IRUse   elementType;
+    IRUse   elementCount;
+
+    IRType* getElementType() { return (IRType*) elementType.usedValue; }
+    IRInst* getElementCount() { return elementCount.usedValue; }
+};
+
+struct IRMatrixType : IRType
+{
+    IRUse   elementType;
+    IRUse   rowCount;
+    IRUse   columnCount;
+
+    IRType* getElementType() { return (IRType*) elementType.usedValue; }
+    IRInst* getRowCount() { return rowCount.usedValue; }
+    IRInst* getColumnCount() { return columnCount.usedValue; }
+};
+
+struct IRArrayType : IRType
+{
+    IRUse   elementType;
+    IRUse   elementCount;
+
+    IRType* getElementType() { return (IRType*) elementType.usedValue; }
+    IRInst* getElementCount() { return elementCount.usedValue; }
+};
+
+
+
+struct IRFuncType : IRType
+{
+    IRUse resultType;
+    // parameter tyeps are varargs...
+
+    IRType* getResultType() { return (IRType*) resultType.usedValue; }
+    UInt getParamCount()
+    {
+        return getArgCount() - 2;
+    }
+    IRType* getParamType(UInt index)
+    {
+        return (IRType*) getArg(2 + index);
+    }
+};
+
+// Address spaces for IR pointers
+enum IRAddressSpace : UInt
+{
+    // A default address space for things like local variables
+    kIRAddressSpace_Default,
+
+    // Address space for HLSL `groupshared` allocations
+    kIRAddressSpace_GroupShared,
+};
+
+struct IRPtrType : IRType
+{
+    IRUse valueType;
+    IRUse addressSpace;
+
+    IRType* getValueType() { return (IRType*) valueType.usedValue; }
+
+    IRAddressSpace getAddressSpace()
+    {
+        return IRAddressSpace(
+            ((IRConstant*)addressSpace.usedValue)->u.intVal);
+    }
+};
+
+struct IRTextureType : IRType
+{
+    IRUse flavor;
+    IRUse elementType;
+
+    IRIntegerValue getFlavor() { return ((IRConstant*) flavor.usedValue)->u.intVal; }
+    IRType* getElementType() { return (IRType*) elementType.usedValue; }
+};
+
+struct IRBufferType : IRType
+{
+    IRUse elementType;
+    IRType* getElementType() { return (IRType*) elementType.usedValue; }
+};
+
+
+struct IRUniformBufferType : IRType
+{
+    IRUse elementType;
+    IRType* getElementType() { return (IRType*) elementType.usedValue; }
+};
+
+struct IRConstantBufferType : IRUniformBufferType {};
+struct IRTextureBufferType : IRUniformBufferType {};
+
+struct IRCall : IRInst
+{
+    IRUse func;
+};
+
+struct IRLoad : IRInst
+{
+    IRUse ptr;
+};
+
+struct IRStore : IRInst
+{
+    IRUse ptr;
+    IRUse val;
+};
+
+struct IRStructField;
+struct IRFieldExtract : IRInst
+{
+    IRUse   base;
+    IRUse   field;
+
+    IRInst* getBase() { return base.usedValue; }
+    IRStructField* getField() { return (IRStructField*) field.usedValue; }
+};
+
+struct IRFieldAddress : IRInst
+{
+    IRUse   base;
+    IRUse   field;
+
+    IRInst* getBase() { return base.usedValue; }
+    IRStructField* getField() { return (IRStructField*) field.usedValue; }
+};
+
+// Terminators
+
+struct IRReturn : IRTerminatorInst
+{};
+
+struct IRReturnVal : IRReturn
+{
+    IRUse val;
+
+    IRInst* getVal() { return val.usedValue; }
+};
+
+struct IRReturnVoid : IRReturn
+{};
+
+struct IRBlock;
+
+struct IRUnconditionalBranch : IRTerminatorInst
+{
+    IRUse block;
+
+    IRBlock* getTargetBlock() { return (IRBlock*)block.usedValue; }
+};
+
+// Special cases of unconditional branch, to handle
+// structured control flow:
+struct IRBreak : IRUnconditionalBranch {};
+struct IRContinue : IRUnconditionalBranch {};
+
+// The start of a loop is a special control-flow
+// instruction, that records relevant information
+// about the loop structure:
+struct IRLoop : IRUnconditionalBranch
+{
+    // The next block after the loop, which
+    // is where we expect control flow to
+    // re-converge, and also where a
+    // `break` will target.
+    IRUse breakBlock;
+
+    // The block where control flow will go
+    // on a `continue`.
+    IRUse continueBlock;
+
+    IRBlock* getBreakBlock() { return (IRBlock*)breakBlock.usedValue; }
+    IRBlock* getContinueBlock() { return (IRBlock*)continueBlock.usedValue; }
+};
+
+struct IRConditionalBranch : IRTerminatorInst
+{
+    IRUse condition;
+    IRUse trueBlock;
+    IRUse falseBlock;
+
+    IRInst* getCondition() { return condition.usedValue; }
+    IRBlock* getTrueBlock() { return (IRBlock*)trueBlock.usedValue; }
+    IRBlock* getFalseBlock() { return (IRBlock*)falseBlock.usedValue; }
+};
+
+// A conditional branch that represent the test inside a loop
+struct IRLoopTest : IRConditionalBranch
+{
+};
+
+// A conditional branch that represents a one-sided `if`:
+//
+//     if( <condition> ) { <trueBlock> }
+//     <falseBlock>
+struct IRIf : IRConditionalBranch
+{
+    IRBlock* getAfterBlock() { return getFalseBlock(); }
+};
+
+// A conditional branch that represents a two-sided `if`:
+//
+//     if( <condition> ) { <trueBlock> }
+//     else              { <falseBlock> }
+//     <afterBlock>
+//
+struct IRIfElse : IRConditionalBranch
+{
+    IRUse afterBlock;
+
+    IRBlock* getAfterBlock() { return (IRBlock*)afterBlock.usedValue; }
+};
+
+struct IRSwizzle : IRReturn
+{
+    IRUse base;
+
+    IRInst* getBase() { return base.usedValue; }
+    UInt getElementCount()
+    {
+        return getArgCount() - 2;
+    }
+    IRInst* getElementIndex(UInt index)
+    {
+        return getArg(index + 2);
+    }
+};
+
+struct IRSwizzleSet : IRReturn
+{
+    IRUse base;
+    IRUse source;
+
+    IRInst* getBase() { return base.usedValue; }
+    IRInst* getSource() { return source.usedValue; }
+    UInt getElementCount()
+    {
+        return getArgCount() - 3;
+    }
+    IRInst* getElementIndex(UInt index)
+    {
+        return getArg(index + 3);
+    }
+};
+
+// "Parent" Instructions (Declarations)
+
+struct IRStructField : IRInst
+{
+    IRType* getFieldType() { return (IRType*) type.usedValue; }
+
+    IRStructField* getNextField() { return (IRStructField*) nextInst; }
+};
+
+struct IRStructDecl : IRParentInst
+{
+    IRStructField* getFirstField() { return (IRStructField*) firstChild; }
+    IRStructField* getLastField() { return (IRStructField*) lastChild; }
+};
+
+
+struct IRVar : IRInst
+{
+    IRPtrType* getType()
+    {
+        return (IRPtrType*)type.usedValue;
+    }
+};
+
+
+// Description of an instruction to be used for global value numbering
+struct IRInstKey
+{
+    IRInst* inst;
+
+    int GetHashCode();
+};
+
+bool operator==(IRInstKey const& left, IRInstKey const& right);
+
+struct IRConstantKey
+{
+    IRConstant* inst;
+
+    int GetHashCode();
+};
+bool operator==(IRConstantKey const& left, IRConstantKey const& right);
+
+struct SharedIRBuilder
+{
+    // The module that will own all of the IR
+    IRModule*       module;
+
+    Dictionary<IRInstKey,       IRInst*>    globalValueNumberingMap;
+    Dictionary<IRConstantKey,   IRConstant*>    constantMap;
+};
+
+struct IRBuilder
+{
+    // Shared state for all IR builders working on the same module
+    SharedIRBuilder*    shared;
+
+    IRModule* getModule() { return shared->module; }
+
+    // The parent instruction to add children to.
+    IRParentInst*   parentInst;
+
+    void addInst(IRParentInst* parent, IRInst* inst);
+    void addInst(IRInst* inst);
+
+    IRType* getBaseType(BaseType flavor);
+    IRType* getBoolType();
+    IRType* getVectorType(IRType* elementType, IRValue* elementCount);
+    IRType* getMatrixType(
+        IRType* elementType,
+        IRValue* rowCount,
+        IRValue* columnCount);
+    IRType* getArrayType(IRType* elementType, IRValue* elementCount);
+    IRType* getArrayType(IRType* elementType);
+
+    IRType* getTypeType();
+    IRType* getVoidType();
+    IRType* getBlockType();
+
+    IRType* getIntrinsicType(
+        IROp op,
+        UInt argCount,
+        IRValue* const* args);
+
+    IRStructDecl* createStructType();
+    IRStructField* createStructField(IRType* fieldType);
+
+    IRType* getFuncType(
+        UInt            paramCount,
+        IRType* const*  paramTypes,
+        IRType*         resultType);
+
+    IRType* getPtrType(
+        IRType*         valueType,
+        IRAddressSpace  addressSpace);
+
+    IRType* getPtrType(
+        IRType* valueType);
+
+    IRValue* getBoolValue(bool value);
+    IRValue* getIntValue(IRType* type, IRIntegerValue value);
+    IRValue* getFloatValue(IRType* type, IRFloatingPointValue value);
+
+    IRInst* emitCallInst(
+        IRType*         type,
+        IRValue*        func,
+        UInt            argCount,
+        IRValue* const* args);
+
+    IRInst* emitIntrinsicInst(
+        IRType*         type,
+        IROp            op,
+        UInt            argCount,
+        IRValue* const* args);
+
+    IRInst* emitConstructorInst(
+        IRType*         type,
+        UInt            argCount,
+        IRValue* const* args);
+
+    IRModule* createModule();
+
+    IRFunc* createFunc();
+
+    IRBlock* createBlock();
+    IRBlock* emitBlock();
+
+    IRParam* emitParam(
+        IRType* type);
+
+    IRVar* emitVar(
+        IRType*         type,
+        IRAddressSpace  addressSpace);
+
+    IRVar* emitVar(
+        IRType* type);
+
+    IRInst* emitLoad(
+        IRValue*    ptr);
+
+    IRInst* emitStore(
+        IRValue*    dstPtr,
+        IRValue*    srcVal);
+
+    IRInst* emitFieldExtract(
+        IRType*         type,
+        IRValue*        base,
+        IRStructField*  field);
+
+    IRInst* emitFieldAddress(
+        IRType*         type,
+        IRValue*        basePtr,
+        IRStructField*  field);
+
+    IRInst* emitElementExtract(
+        IRType*     type,
+        IRValue*    base,
+        IRValue*    index);
+
+    IRInst* emitElementAddress(
+        IRType*     type,
+        IRValue*    basePtr,
+        IRValue*    index);
+
+    IRInst* emitSwizzle(
+        IRType*         type,
+        IRValue*        base,
+        UInt            elementCount,
+        IRValue* const* elementIndices);
+
+    IRInst* emitSwizzle(
+        IRType*         type,
+        IRValue*        base,
+        UInt            elementCount,
+        UInt const*     elementIndices);
+
+    IRInst* emitSwizzleSet(
+        IRType*         type,
+        IRValue*        base,
+        IRValue*        source,
+        UInt            elementCount,
+        IRValue* const* elementIndices);
+
+    IRInst* emitSwizzleSet(
+        IRType*         type,
+        IRValue*        base,
+        IRValue*        source,
+        UInt            elementCount,
+        UInt const*     elementIndices);
+
+    IRInst* emitReturn(
+        IRValue*    val);
+
+    IRInst* emitReturn();
+
+    IRInst* emitBranch(
+        IRBlock*    block);
+
+    IRInst* emitBreak(
+        IRBlock*    target);
+
+    IRInst* emitContinue(
+        IRBlock*    target);
+
+    IRInst* emitLoop(
+        IRBlock*    target,
+        IRBlock*    breakBlock,
+        IRBlock*    continueBlock);
+
+    IRInst* emitBranch(
+        IRValue*    val,
+        IRBlock*    trueBlock,
+        IRBlock*    falseBlock);
+
+    IRInst* emitIf(
+        IRValue*    val,
+        IRBlock*    trueBlock,
+        IRBlock*    afterBlock);
+
+    IRInst* emitIfElse(
+        IRValue*    val,
+        IRBlock*    trueBlock,
+        IRBlock*    falseBlock,
+        IRBlock*    afterBlock);
+
+    IRInst* emitLoopTest(
+        IRValue*    val,
+        IRBlock*    bodyBlock,
+        IRBlock*    breakBlock);
+
+    IRDecoration* addDecorationImpl(
+        IRInst*         inst,
+        UInt            decorationSize,
+        IRDecorationOp  op);
+
+    template<typename T>
+    T* addDecoration(IRInst* inst, IRDecorationOp op)
+    {
+        return (T*) addDecorationImpl(inst, sizeof(T), op);
+    }
+
+    template<typename T>
+    T* addDecoration(IRInst* inst)
+    {
+        return (T*) addDecorationImpl(inst, sizeof(T), IRDecorationOp(T::kDecorationOp));
+    }
+
+    IRHighLevelDeclDecoration* addHighLevelDeclDecoration(IRInst* inst, Decl* decl);
+    IRLayoutDecoration* addLayoutDecoration(IRInst* inst, Layout* layout);
+};
+
+}
+
+#endif
diff --git a/source/slang/ir.cpp b/source/slang/ir.cpp
index 3a6410125..c48880cab 100644
--- a/source/slang/ir.cpp
+++ b/source/slang/ir.cpp
@@ -1,5 +1,6 @@
 // ir.cpp
 #include "ir.h"
+#include "ir-insts.h"
 
 #include "../core/basic.h"
 
@@ -65,7 +66,12 @@ namespace Slang
         return nullptr;
     }
 
-    //
+    // IRFunc
+
+    IRType* IRFunc::getResultType() { return getType()->getResultType(); }
+    UInt IRFunc::getParamCount() { return getType()->getParamCount(); }
+    IRType* IRFunc::getParamType(UInt index) { return getType()->getParamType(index); }
+
 
     IRParam* IRFunc::getFirstParam()
     {
@@ -81,6 +87,8 @@ namespace Slang
         return (IRParam*) firstInst;
     }
 
+    // IRParam
+
     IRParam* IRParam::getNextParam()
     {
         auto next = nextInst;
@@ -94,6 +102,36 @@ namespace Slang
 
     //
 
+    bool isTerminatorInst(IROp op)
+    {
+        switch (op)
+        {
+        default:
+            return false;
+
+        case kIROp_ReturnVal:
+        case kIROp_ReturnVoid:
+        case kIROp_unconditionalBranch:
+        case kIROp_conditionalBranch:
+        case kIROp_break:
+        case kIROp_continue:
+        case kIROp_loop:
+        case kIROp_if:
+        case kIROp_ifElse:
+        case kIROp_loopTest:
+            return true;
+        }
+    }
+
+    bool isTerminatorInst(IRInst* inst)
+    {
+        if (!inst) return false;
+        return isTerminatorInst(inst->op);
+    }
+
+
+    //
+
     // Add an instruction to a specific parent
     void IRBuilder::addInst(IRParentInst* parent, IRInst* inst)
     {
@@ -306,6 +344,28 @@ namespace Slang
             varArgs);
     }
 
+    template<typename T>
+    static T* createInstWithTrailingArgs(
+        IRBuilder*      builder,
+        IROp            op,
+        IRType*         type,
+        IRValue*        arg1,
+        UInt            varArgCount,
+        IRValue* const* varArgs)
+    {
+        IRValue* fixedArgs[] = { arg1 };
+        UInt fixedArgCount = sizeof(fixedArgs) / sizeof(fixedArgs[0]);
+
+        return (T*)createInstImpl(
+            builder,
+            sizeof(T) + varArgCount * sizeof(IRUse),
+            op,
+            type,
+            fixedArgCount,
+            fixedArgs,
+            varArgCount,
+            varArgs);
+    }
     //
 
     bool operator==(IRInstKey const& left, IRInstKey const& right)
@@ -637,6 +697,8 @@ namespace Slang
     {
         switch( flavor )
         {
+        case BaseType::Void:    return getVoidType();
+
         case BaseType::Bool:    return getBaseTypeImpl(this, kIROp_BoolType);
         case BaseType::Float:   return getBaseTypeImpl(this, kIROp_Float32Type);
         case BaseType::Int:     return getBaseTypeImpl(this, kIROp_Int32Type);
@@ -677,6 +739,34 @@ namespace Slang
             columnCount);
     }
 
+    IRType* IRBuilder::getArrayType(IRType* elementType, IRValue* elementCount)
+    {
+        // The client requests an unsized array by passing `nullptr` for
+        // the `elementCount`.
+        //
+        // We currently encode an unsized array as an ordinary array with
+        // zero elements. TODO: carefully consider this choice.
+        if (!elementCount)
+        {
+            elementCount = getIntValue(
+                getBaseType(BaseType::Int),
+                0);
+        }
+
+        return findOrEmitInst<IRArrayType>(
+            this,
+            kIROp_arrayType,
+            getTypeType(),
+            elementType,
+            elementCount);
+    }
+
+    IRType* IRBuilder::getArrayType(IRType* elementType)
+    {
+        return getArrayType(elementType, nullptr);
+    }
+
+
     IRType* IRBuilder::getTypeType()
     {
         return findOrEmitInst<IRType>(
@@ -753,21 +843,38 @@ namespace Slang
     }
 
     IRType* IRBuilder::getPtrType(
-        IRType* valueType)
+        IRType*         valueType,
+        IRAddressSpace  addressSpace)
     {
+        auto uintType = getBaseType(BaseType::UInt);
+        auto irAddressSpace = getIntValue(uintType, addressSpace);
+
         auto inst = findOrEmitInst<IRPtrType>(
             this,
             kIROp_PtrType,
             getTypeType(),
-            1,
-            (IRValue* const*) &valueType);
+            valueType,
+            irAddressSpace);
         return inst;
     }
 
 
-    IRValue* IRBuilder::getBoolValue(bool value)
+    IRType* IRBuilder::getPtrType(
+        IRType* valueType)
     {
-        SLANG_UNIMPLEMENTED_X("IR");
+        return getPtrType(valueType, kIRAddressSpace_Default);
+    }
+
+
+    IRValue* IRBuilder::getBoolValue(bool inValue)
+    {
+        IRIntegerValue value = inValue;
+        return findOrEmitConstant(
+            this,
+            kIROp_boolConst,
+            getBoolType(),
+            sizeof(value),
+            &value);
     }
 
     IRValue* IRBuilder::getIntValue(IRType* type, IRIntegerValue value)
@@ -883,9 +990,10 @@ namespace Slang
     }
 
     IRVar* IRBuilder::emitVar(
-        IRType* type)
+        IRType*         type,
+        IRAddressSpace  addressSpace)
     {
-        auto allocatedType = getPtrType(type);
+        auto allocatedType = getPtrType(type, addressSpace);
         auto inst = createInst<IRVar>(
             this,
             kIROp_Var,
@@ -894,6 +1002,13 @@ namespace Slang
         return inst;
     }
 
+
+    IRVar* IRBuilder::emitVar(
+        IRType* type)
+    {
+        return emitVar(type, kIRAddressSpace_Default);
+    }
+
     IRInst* IRBuilder::emitLoad(
         IRValue*    ptr)
     {
@@ -996,6 +1111,83 @@ namespace Slang
         return inst;
     }
 
+    IRInst* IRBuilder::emitSwizzle(
+        IRType*         type,
+        IRValue*        base,
+        UInt            elementCount,
+        IRValue* const* elementIndices)
+    {
+        auto inst = createInstWithTrailingArgs<IRSwizzle>(
+            this,
+            kIROp_swizzle,
+            type,
+            base,
+            elementCount,
+            elementIndices);
+
+        addInst(inst);
+        return inst;
+    }
+
+    IRInst* IRBuilder::emitSwizzle(
+        IRType*         type,
+        IRValue*        base,
+        UInt            elementCount,
+        UInt const*     elementIndices)
+    {
+        auto intType = getBaseType(BaseType::Int);
+
+        IRValue* irElementIndices[4];
+        for (UInt ii = 0; ii < elementCount; ++ii)
+        {
+            irElementIndices[ii] = getIntValue(intType, elementIndices[ii]);
+        }
+
+        return emitSwizzle(type, base, elementCount, irElementIndices);
+    }
+
+
+    IRInst* IRBuilder::emitSwizzleSet(
+        IRType*         type,
+        IRValue*        base,
+        IRValue*        source,
+        UInt            elementCount,
+        IRValue* const* elementIndices)
+    {
+        IRValue* fixedArgs[] = { base, source };
+        UInt fixedArgCount = sizeof(fixedArgs) / sizeof(fixedArgs[0]);
+
+        auto inst = createInstWithTrailingArgs<IRSwizzleSet>(
+            this,
+            kIROp_swizzleSet,
+            type,
+            fixedArgCount,
+            fixedArgs,
+            elementCount,
+            elementIndices);
+
+        addInst(inst);
+        return inst;
+    }
+
+    IRInst* IRBuilder::emitSwizzleSet(
+        IRType*         type,
+        IRValue*        base,
+        IRValue*        source,
+        UInt            elementCount,
+        UInt const*     elementIndices)
+    {
+        auto intType = getBaseType(BaseType::Int);
+
+        IRValue* irElementIndices[4];
+        for (UInt ii = 0; ii < elementCount; ++ii)
+        {
+            irElementIndices[ii] = getIntValue(intType, elementIndices[ii]);
+        }
+
+        return emitSwizzleSet(type, base, source, elementCount, irElementIndices);
+    }
+
     IRInst* IRBuilder::emitReturn(
         IRValue*    val)
     {
@@ -1018,6 +1210,133 @@ namespace Slang
         return inst;
     }
 
+    IRInst* IRBuilder::emitBranch(
+        IRBlock*    block)
+    {
+        auto inst = createInst<IRUnconditionalBranch>(
+            this,
+            kIROp_unconditionalBranch,
+            getVoidType(),
+            block);
+        addInst(inst);
+        return inst;
+    }
+
+    IRInst* IRBuilder::emitBreak(
+        IRBlock*    target)
+    {
+        auto inst = createInst<IRBreak>(
+            this,
+            kIROp_break,
+            getVoidType(),
+            target);
+        addInst(inst);
+        return inst;
+    }
+
+    IRInst* IRBuilder::emitContinue(
+        IRBlock*    target)
+    {
+        auto inst = createInst<IRContinue>(
+            this,
+            kIROp_continue,
+            getVoidType(),
+            target);
+        addInst(inst);
+        return inst;
+    }
+
+    IRInst* IRBuilder::emitLoop(
+        IRBlock*    target,
+        IRBlock*    breakBlock,
+        IRBlock*    continueBlock)
+    {
+        IRInst* args[] = { target, breakBlock, continueBlock };
+        UInt argCount = sizeof(args) / sizeof(args[0]);
+
+        auto inst = createInst<IRLoop>(
+            this,
+            kIROp_loop,
+            getVoidType(),
+            argCount,
+            args);
+        addInst(inst);
+        return inst;
+    }
+
+    IRInst* IRBuilder::emitBranch(
+        IRValue*    val,
+        IRBlock*    trueBlock,
+        IRBlock*    falseBlock)
+    {
+        IRInst* args[] = { val, trueBlock, falseBlock };
+        UInt argCount = sizeof(args) / sizeof(args[0]);
+
+        auto inst = createInst<IRConditionalBranch>(
+            this,
+            kIROp_conditionalBranch,
+            getVoidType(),
+            argCount,
+            args);
+        addInst(inst);
+        return inst;
+    }
+
+    IRInst* IRBuilder::emitIf(
+        IRValue*    val,
+        IRBlock*    trueBlock,
+        IRBlock*    afterBlock)
+    {
+        IRInst* args[] = { val, trueBlock, afterBlock };
+        UInt argCount = sizeof(args) / sizeof(args[0]);
+
+        auto inst = createInst<IRIf>(
+            this,
+            kIROp_if,
+            getVoidType(),
+            argCount,
+            args);
+        addInst(inst);
+        return inst;
+    }
+
+    IRInst* IRBuilder::emitIfElse(
+        IRValue*    val,
+        IRBlock*    trueBlock,
+        IRBlock*    falseBlock,
+        IRBlock*    afterBlock)
+    {
+        IRInst* args[] = { val, trueBlock, falseBlock, afterBlock };
+        UInt argCount = sizeof(args) / sizeof(args[0]);
+
+        auto inst = createInst<IRIfElse>(
+            this,
+            kIROp_ifElse,
+            getVoidType(),
+            argCount,
+            args);
+        addInst(inst);
+        return inst;
+    }
+
+    IRInst* IRBuilder::emitLoopTest(
+        IRValue*    val,
+        IRBlock*    bodyBlock,
+        IRBlock*    breakBlock)
+    {
+        IRInst* args[] = { val, bodyBlock, breakBlock };
+        UInt argCount = sizeof(args) / sizeof(args[0]);
+
+        auto inst = createInst<IRLoopTest>(
+            this,
+            kIROp_loopTest,
+            getVoidType(),
+            argCount,
+            args);
+        addInst(inst);
+        return inst;
+    }
+
     IRDecoration* IRBuilder::addDecorationImpl(
         IRInst*         inst,
         UInt            decorationSize,
@@ -1053,7 +1372,7 @@ namespace Slang
 
     struct IRDumpContext
     {
-        FILE*   file;
+        StringBuilder* builder;
         int     indent;
     };
 
@@ -1061,14 +1380,16 @@ namespace Slang
         IRDumpContext*  context,
         char const*     text)
     {
-        fprintf(context->file, "%s", text);
+        context->builder->append(text);
     }
 
     static void dump(
         IRDumpContext*  context,
         UInt            val)
     {
-        fprintf(context->file, "%llu", (unsigned long long)val);
+        context->builder->append(val);
+
+//        fprintf(context->file, "%llu", (unsigned long long)val);
     }
 
     static void dumpIndent(
@@ -1076,7 +1397,7 @@ namespace Slang
     {
         for (int ii = 0; ii < context->indent; ++ii)
         {
-            dump(context, "  ");
+            dump(context, "\t");
         }
     }
 
@@ -1088,79 +1409,318 @@ namespace Slang
         {
             dump(context, "<null>");
         }
-        else
+        else if(inst->id)
         {
             dump(context, "%");
             dump(context, inst->id);
         }
+        else
+        {
+            dump(context, "_");
+        }
     }
 
-    static void dumpInst(
+    static void dumpType(
+        IRDumpContext*  context,
+        IRType*         type);
+
+    static void dumpOperand(
         IRDumpContext*  context,
         IRInst*         inst)
     {
-        dumpIndent(context);
         if (!inst)
         {
-            dump(context, "<null>");
+            dump(context, "undef");
+            return;
         }
 
-        // TODO: need to display a name for the result...
+        switch (inst->op)
+        {
+        case kIROp_IntLit:
+            dump(context, ((IRConstant*)inst)->u.intVal);
+            return;
 
-        auto op = inst->op;
-        auto opInfo = &kIROpInfos[op];
+        case kIROp_FloatLit:
+            dump(context, ((IRConstant*)inst)->u.floatVal);
+            return;
 
-        if (inst->id)
+        case kIROp_boolConst:
+            dump(context, ((IRConstant*)inst)->u.intVal ? "true" : "false");
+            return;
+
+        case kIROp_TypeType:
+            dumpType(context, (IRType*)inst);
+            return;
+
+        default:
+            break;
+        }
+
+        auto type = inst->getType();
+        if (type)
         {
-            dumpID(context, inst);
-            dump(context, " = ");
+            switch (type->op)
+            {
+            case kIROp_TypeType:
+                dumpType(context, (IRType*)inst);
+                return;
+
+            default:
+                break;
+            }
         }
 
-        dump(context, opInfo->name);
 
-        // TODO: dump operands
-        uint32_t argCount = inst->argCount;
-        for (uint32_t ii = 0; ii < argCount; ++ii)
+        dumpID(context, inst);
+    }
+
+    static void dumpType(
+        IRDumpContext*  context,
+        IRType*         type)
+    {
+        if (!type)
         {
-            if (ii != 0)
-                dump(context, ", ");
-            else
+            dumpID(context, type);
+            return;
+        }
+
+        auto op = type->op;
+        auto opInfo = kIROpInfos[op];
+
+        switch (op)
+        {
+        case kIROp_StructType:
+            dumpID(context, type);
+            break;
+
+        default:
             {
-                dump(context, " ");
+                dump(context, opInfo.name);
+                UInt argCount = type->getArgCount();
+
+                if (argCount > 1)
+                {
+                    dump(context, "<");
+                    for (UInt aa = 1; aa < argCount; ++aa)
+                    {
+                        if (aa != 1) dump(context, ",");
+                        dumpOperand(context, type->getArg(aa));
+
+                    }
+                    dump(context, ">");
+                }
             }
+            break;
+        }
+    }
 
-            auto argVal = inst->getArgs()[ii].usedValue;
+    static void dumpInstTypeClause(
+        IRDumpContext*  context,
+        IRType*         type)
+    {
+        dump(context, "\t: ");
+        dumpType(context, type);
 
-            // TODO: actually print the damn operand...
+    }
 
-            dumpID(context, argVal);
-        }
+    static void dumpInst(
+        IRDumpContext*  context,
+        IRInst*         inst);
 
-        dump(context, "\n");
+    static void dumpChildrenRaw(
+        IRDumpContext*  context,
+        IRParentInst*   parent)
+    {
+        for (auto ii = parent->firstChild; ii; ii = ii->nextInst)
+        {
+            dumpInst(context, ii);
+        }
+    }
 
+    static void dumpChildren(
+        IRDumpContext*  context,
+        IRInst*         inst)
+    {
+        auto op = inst->op;
+        auto opInfo = &kIROpInfos[op];
         if (opInfo->flags & kIROpFlag_Parent)
         {
             dumpIndent(context);
             dump(context, "{\n");
             context->indent++;
             auto parent = (IRParentInst*)inst;
-            for (auto ii = parent->firstChild; ii; ii = ii->nextInst)
-            {
-                dumpInst(context, ii);
-            }
+            dumpChildrenRaw(context, parent);
             context->indent--;
             dumpIndent(context);
             dump(context, "}\n");
         }
     }
+    static void dumpInst(
+        IRDumpContext*  context,
+        IRInst*         inst)
+    {
+        if (!inst)
+        {
+            dumpIndent(context);
+            dump(context, "<null>");
+            return;
+        }
+
+        auto op = inst->op;
+
+        // There are several ops we want to special-case here,
+        // so that they will be more pleasant to look at.
+        //
+        switch (op)
+        {
+        case kIROp_Module:
+            dumpIndent(context);
+            dump(context, "module\n");
+            dumpChildren(context, inst);
+            return;
+
+        case kIROp_Func:
+            {
+                IRFunc* func = (IRFunc*)inst;
+                dump(context, "\n");
+                dumpIndent(context);
+                dump(context, "func ");
+                dumpID(context, func);
+                dump(context, "(\n");
+                context->indent++;
+                for (auto pp = func->getFirstParam(); pp; pp = pp->getNextParam())
+                {
+                    if (pp != func->getFirstParam())
+                        dump(context, ",\n");
+
+                    dumpIndent(context);
+                    dump(context, "param ");
+                    dumpID(context, pp);
+                    dumpInstTypeClause(context, pp->getType());
+                }
+                context->indent--;
+                dump(context, ")\n");
+
+                dumpIndent(context);
+                dump(context, "{\n");
+                context->indent++;
+
+                for (auto bb = func->getFirstBlock(); bb; bb = bb->getNextBlock())
+                {
+                    if (bb != func->getFirstBlock())
+                        dump(context, "\n");
+                    dumpInst(context, bb);
+                }
+
+                context->indent--;
+                dump(context, "}\n");
+            }
+            return;
+
+        case kIROp_TypeType:
+        case kIROp_Param:
+        case kIROp_IntLit:
+        case kIROp_FloatLit:
+        case kIROp_boolConst:
+            // Don't dump here
+            return;
+
+        case kIROp_Block:
+            {
+                IRBlock* block = (IRBlock*)inst;
+
+                context->indent--;
+                dump(context, "block ");
+                dumpID(context, block);
+                dump(context, ":\n");
+                context->indent++;
+
+                dumpChildrenRaw(context, block);
+            }
+            return;
+
+        default:
+            break;
+        }
 
-    void dumpIR(IRModule* module)
+        // We also want to special-case based on the *type*
+        // of the instruction
+        auto type = inst->getType();
+        if (type && type->op == kIROp_TypeType)
+        {
+            // We probably don't want to print most types
+            // when producing "friendly" output.
+            switch (type->op)
+            {
+            case kIROp_StructType:
+                break;
+
+            default:
+                return;
+            }
+        }
+
+
+        // Okay, we have a seemingly "ordinary" op now
+        dumpIndent(context);
+
+        auto opInfo = &kIROpInfos[op];
+
+        if (type && type->op == kIROp_TypeType)
+        {
+            dump(context, "type ");
+            dumpID(context, inst);
+            dump(context, "\t= ");
+        }
+        else if (type && type->op == kIROp_VoidType)
+        {
+        }
+        else
+        {
+            dump(context, "let  ");
+            dumpID(context, inst);
+            dumpInstTypeClause(context, type);
+            dump(context, "\t= ");
+        }
+
+
+        dump(context, opInfo->name);
+
+        uint32_t argCount = inst->argCount;
+        dump(context, "(");
+        for (uint32_t ii = 1; ii < argCount; ++ii)
+        {
+            if (ii != 1)
+                dump(context, ", ");
+
+            auto argVal = inst->getArgs()[ii].usedValue;
+
+            dumpOperand(context, argVal);
+        }
+        dump(context, ")");
+
+        dump(context, "\n");
+
+        // The instruction might have children,
+        // so we need to handle those here
+        dumpChildren(context, inst);
+    }
+
+    void printSlangIRAssembly(StringBuilder& builder, IRModule* module)
     {
         IRDumpContext context;
-        context.file = stderr;
+        context.builder = &builder;
         context.indent = 0;
 
-        dumpInst(&context, module);
+        dumpChildrenRaw(&context, module);
     }
 
+    String getSlangIRAssembly(IRModule* module)
+    {
+        StringBuilder sb;
+        printSlangIRAssembly(sb, module);
+        return sb;
+    }
+
+
 }
diff --git a/source/slang/ir.h b/source/slang/ir.h
index 6e4a25fe1..9b271b09b 100644
--- a/source/slang/ir.h
+++ b/source/slang/ir.h
@@ -9,7 +9,6 @@
 
 #include "../core/basic.h"
 
-
 namespace Slang {
 
 // TODO(tfoley): We should ditch this enumeration
@@ -143,6 +142,9 @@ enum IRDecorationOp : uint16_t
 {
     kIRDecorationOp_HighLevelDecl,
     kIRDecorationOp_Layout,
+    kIRDecorationOp_EntryPoint,
+    kIRDecorationOp_ComputeThreadGroupSize,
+    kIRDecorationOp_LoopControl,
 };
 
 // A "decoration" that gets applied to an instruction.
@@ -220,27 +222,6 @@ struct IRInst
 // All existing uses of `IRValue` should move to `IRInst`
 typedef IRInst IRValue;
 
-class Decl;
-
-// Associates an IR-level decoration with a source declaration
-// in the high-level AST, that can be used to extract
-// additional information that informs code emission.
-struct IRHighLevelDeclDecoration : IRDecoration
-{
-    enum { kDecorationOp = kIRDecorationOp_HighLevelDecl };
-
-    Decl* decl;
-};
-
-// Associates an IR-level decoration with a source layout
-struct IRLayoutDecoration : IRDecoration
-{
-    enum { kDecorationOp = kIRDecorationOp_Layout };
-
-    Layout* layout;
-};
-
-
 typedef long long IRIntegerValue;
 typedef double IRFloatingPointValue;
 
@@ -266,126 +247,13 @@ struct IRType : IRInst
 {
 };
 
-struct IRVectorType : IRType
-{
-    IRUse   elementType;
-    IRUse   elementCount;
-
-    IRType* getElementType() { return (IRType*) elementType.usedValue; }
-    IRInst* getElementCount() { return elementCount.usedValue; }
-};
-
-struct IRMatrixType : IRType
-{
-    IRUse   elementType;
-    IRUse   rowCount;
-    IRUse   columnCount;
-
-    IRType* getElementType() { return (IRType*) elementType.usedValue; }
-    IRInst* getRowCount() { return rowCount.usedValue; }
-    IRInst* getColumnCount() { return columnCount.usedValue; }
-};
-
-struct IRFuncType : IRType
-{
-    IRUse resultType;
-    // parameter tyeps are varargs...
-
-    IRType* getResultType() { return (IRType*) resultType.usedValue; }
-    UInt getParamCount()
-    {
-        return getArgCount() - 2;
-    }
-    IRType* getParamType(UInt index)
-    {
-        return (IRType*) getArg(2 + index);
-    }
-};
-
-struct IRPtrType : IRType
-{
-    IRUse valueType;
-
-    IRType* getValueType() { return (IRType*) valueType.usedValue; }
-};
-
-struct IRTextureType : IRType
-{
-    IRUse flavor;
-    IRUse elementType;
-
-    IRIntegerValue getFlavor() { return ((IRConstant*) flavor.usedValue)->u.intVal; }
-    IRType* getElementType() { return (IRType*) elementType.usedValue; }
-};
-
-struct IRBufferType : IRType
-{
-    IRUse elementType;
-    IRType* getElementType() { return (IRType*) elementType.usedValue; }
-};
-
-
-struct IRUniformBufferType : IRType
-{
-    IRUse elementType;
-    IRType* getElementType() { return (IRType*) elementType.usedValue; }
-};
-
-struct IRConstantBufferType : IRUniformBufferType {};
-struct IRTextureBufferType : IRUniformBufferType {};
-
-struct IRCall : IRInst
-{
-    IRUse func;
-};
-
-struct IRLoad : IRInst
-{
-    IRUse ptr;
-};
-
-struct IRStore : IRInst
-{
-    IRUse ptr;
-    IRUse val;
-};
-
-struct IRStructField;
-struct IRFieldExtract : IRInst
-{
-    IRUse   base;
-    IRUse   field;
-
-    IRInst* getBase() { return base.usedValue; }
-    IRStructField* getField() { return (IRStructField*) field.usedValue; }
-};
-
-struct IRFieldAddress : IRInst
-{
-    IRUse   base;
-    IRUse   field;
-
-    IRInst* getBase() { return base.usedValue; }
-    IRStructField* getField() { return (IRStructField*) field.usedValue; }
-};
-
-
 // A instruction that ends a basic block (usually because of control flow)
 struct IRTerminatorInst : IRInst
 {};
 
-struct IRReturn : IRTerminatorInst
-{};
-
-struct IRReturnVal : IRReturn
-{
-    IRUse val;
-
-    IRInst* getVal() { return val.usedValue; }
-};
+bool isTerminatorInst(IROp op);
+bool isTerminatorInst(IRInst* inst);
 
-struct IRReturnVoid : IRReturn
-{};
 
 // A parent instruction contains a sequence of other instructions
 //
@@ -398,20 +266,6 @@ struct IRParentInst : IRInst
     IRInst* lastChild;
 };
 
-struct IRStructField : IRInst
-{
-    IRType* getFieldType() { return (IRType*) type.usedValue; }
-
-    IRStructField* getNextField() { return (IRStructField*) nextInst; }
-};
-
-struct IRStructDecl : IRParentInst
-{
-    IRStructField* getFirstField() { return (IRStructField*) firstChild; }
-    IRStructField* getLastField() { return (IRStructField*) lastChild; }
-};
-
-
 // A basic block is a parent instruction that adds the constraint
 // that all the children need to be "ordinary" instructions (so
 // no function declarations, or nested blocks). We also expect
@@ -425,6 +279,8 @@ struct IRBlock : IRParentInst
 
     IRBlock* getPrevBlock() { return (IRBlock*) prevInst; }
     IRBlock* getNextBlock() { return (IRBlock*) nextInst; }
+
+    IRFunc* getParent() { return (IRFunc*)parent; }
 };
 
 // A function parameter is represented by an instruction
@@ -434,8 +290,7 @@ struct IRParam : IRInst
     IRParam* getNextParam();
 };
 
-struct IRVar : IRInst
-{};
+struct IRFuncType;
 
 // A function is a parent to zero or more blocks of instructions.
 //
@@ -445,9 +300,9 @@ struct IRFunc : IRParentInst
 {
     IRFuncType* getType() { return (IRFuncType*) type.usedValue; }
 
-    IRType* getResultType() { return getType()->getResultType(); }
-    UInt getParamCount() { return getType()->getParamCount(); }
-    IRType* getParamType(UInt index) { return getType()->getParamType(index); }
+    IRType* getResultType();
+    UInt getParamCount();
+    IRType* getParamType(UInt index);
 
     IRBlock* getFirstBlock() { return (IRBlock*) firstChild; }
     IRBlock* getLastBlock() { return (IRBlock*) lastChild; }
@@ -465,163 +320,10 @@ struct IRModule : IRParentInst
     IRInstID    idCounter;
 };
 
-// Description of an instruction to be used for global value numbering
-struct IRInstKey
-{
-    IRInst* inst;
-
-    int GetHashCode();
-};
-
-bool operator==(IRInstKey const& left, IRInstKey const& right);
-
-struct IRConstantKey
-{
-    IRConstant* inst;
-
-    int GetHashCode();
-};
-bool operator==(IRConstantKey const& left, IRConstantKey const& right);
-
-struct SharedIRBuilder
-{
-    // The module that will own all of the IR
-    IRModule*       module;
-
-    Dictionary<IRInstKey,       IRInst*>    globalValueNumberingMap;
-    Dictionary<IRConstantKey,   IRConstant*>    constantMap;
-};
-
-struct IRBuilder
-{
-    // Shared state for all IR builders working on the same module
-    SharedIRBuilder*    shared;
-
-    IRModule* getModule() { return shared->module; }
-
-    // The parent instruction to add children to.
-    IRParentInst*   parentInst;
-
-    void addInst(IRParentInst* parent, IRInst* inst);
-    void addInst(IRInst* inst);
-
-    IRType* getBaseType(BaseType flavor);
-    IRType* getBoolType();
-    IRType* getVectorType(IRType* elementType, IRValue* elementCount);
-    IRType* getMatrixType(
-        IRType* elementType,
-        IRValue* rowCount,
-        IRValue* columnCount);
-    IRType* getTypeType();
-    IRType* getVoidType();
-    IRType* getBlockType();
-
-    IRType* getIntrinsicType(
-        IROp op,
-        UInt argCount,
-        IRValue* const* args);
-
-    IRStructDecl* createStructType();
-    IRStructField* createStructField(IRType* fieldType);
-
-    IRType* getFuncType(
-        UInt            paramCount,
-        IRType* const*  paramTypes,
-        IRType*         resultType);
-
-    IRType* getPtrType(
-        IRType* valueType);
-
-    IRValue* getBoolValue(bool value);
-    IRValue* getIntValue(IRType* type, IRIntegerValue value);
-    IRValue* getFloatValue(IRType* type, IRFloatingPointValue value);
-
-    IRInst* emitCallInst(
-        IRType*         type,
-        IRValue*        func,
-        UInt            argCount,
-        IRValue* const* args);
-
-    IRInst* emitIntrinsicInst(
-        IRType*         type,
-        IROp            op,
-        UInt            argCount,
-        IRValue* const* args);
-
-    IRInst* emitConstructorInst(
-        IRType*         type,
-        UInt            argCount,
-        IRValue* const* args);
-
-    IRModule* createModule();
-
-    IRFunc* createFunc();
-
-    IRBlock* createBlock();
-    IRBlock* emitBlock();
-
-    IRParam* emitParam(
-        IRType* type);
-
-    IRVar* emitVar(
-        IRType* type);
-
-    IRInst* emitLoad(
-        IRValue*    ptr);
-
-    IRInst* emitStore(
-        IRValue*    dstPtr,
-        IRValue*    srcVal);
-
-    IRInst* emitFieldExtract(
-        IRType*         type,
-        IRValue*        base,
-        IRStructField*  field);
-
-    IRInst* emitFieldAddress(
-        IRType*         type,
-        IRValue*        basePtr,
-        IRStructField*  field);
-
-    IRInst* emitElementExtract(
-        IRType*     type,
-        IRValue*    base,
-        IRValue*    index);
-
-    IRInst* emitElementAddress(
-        IRType*     type,
-        IRValue*    basePtr,
-        IRValue*    index);
-
-
-    IRInst* emitReturn(
-        IRValue*    val);
-
-    IRInst* emitReturn();
-
-    IRDecoration* addDecorationImpl(
-        IRInst*         inst,
-        UInt            decorationSize,
-        IRDecorationOp  op);
-
-    template<typename T>
-    T* addDecoration(IRInst* inst, IRDecorationOp op)
-    {
-        return (T*) addDecorationImpl(inst, sizeof(T), op);
-    }
-
-    template<typename T>
-    T* addDecoration(IRInst* inst)
-    {
-        return (T*) addDecorationImpl(inst, sizeof(T), IRDecorationOp(T::kDecorationOp));
-    }
-
-    IRHighLevelDeclDecoration* addHighLevelDeclDecoration(IRInst* inst, Decl* decl);
-    IRLayoutDecoration* addLayoutDecoration(IRInst* inst, Layout* layout);
-};
-
-void dumpIR(IRModule* module);
+void printSlangIRAssembly(StringBuilder& builder, IRModule* module);
+String getSlangIRAssembly(IRModule* module);
 
 }
 
+
 #endif
diff --git a/source/slang/lower-to-ir.cpp b/source/slang/lower-to-ir.cpp
index 10b4aefca..5ee6d5460 100644
--- a/source/slang/lower-to-ir.cpp
+++ b/source/slang/lower-to-ir.cpp
@@ -2,44 +2,130 @@
 #include "lower-to-ir.h"
 
 #include "ir.h"
+#include "ir-insts.h"
 #include "type-layout.h"
 #include "visitor.h"
 
 namespace Slang
 {
 
-struct BoundMemberInfo;
+// This file implements lowering of the Slang AST to a simpler SSA
+// intermediate representation.
+//
+// IR is generated in a context (`IRGenContext`), which tracks the current
+// location in the IR where code should be emitted (e.g., what basic
+// block to add instructions to). Lowering a statement will emit some
+// number of instructions to the context, and possibly change the
+// insertion point (because of control flow).
+//
+// When lowering an expression we have a more interesting challenge, for
+// two main reasons:
+//
+// 1. There might be types that are representible in the AST, but which
+//    we don't want to support natively in the IR. An example is a `struct`
+//    type with both ordinary and resource-type members; we might want to
+//    split values with such a type into distinct values during lowering.
+//
+// 2. We need to handle the difference between l-value and r-value expressions,
+//    and in particular the fact that HLSL/Slang supports complicated sorts
+//    of l-values (e.g., `someVector.zxy` is an l-value, even though it can't
+//    be represented by a single pointer), and also allows l-values to appear
+//    in multiple contexts (not just the left-hand side of assignment, but
+//    also as an argument to match an `out` or `in out` parameter).
+//
+// Our solution to both of these problems is the same. Rather than having
+// the lowering of an expression return a single IR-level value (`IRInst*`),
+// we have it return a more complex type (`LoweredValInfo`) which can represent
+// a wider range of conceptual "values" which might correspond to multiple IR-level
+// values, and/or represent a pointer to an l-value rather than the r-value itself.
+
+// We want to keep the representation of a `LoweringValInfo` relatively light
+// - right now it is just a single pointer plus a "tag" to distinguish the cases.
+//
+// This means that cases that can't fit in a single pointer need a heap allocation
+// to store their payload. For simplicity we represent all of these with a class
+// hierarchy:
+//
+struct ExtendedValueInfo : RefObject
+{};
 
-struct SubscriptInfo : RefObject
+// This case is used to indicate a value that is a reference
+// to an AST-level subscript declaration.
+//
+struct SubscriptInfo : ExtendedValueInfo
 {
     DeclRef<SubscriptDecl> declRef;
 };
 
-struct BoundSubscriptInfo : RefObject
+// This case is used to indicate a reference to an AST-level
+// subscript operation bound to particular arguments.
+//
+// For example in a case like this:
+//
+//     RWStructuredBuffer<Foo> gBuffer;
+//     ... gBuffer[someIndex] ...
+//
+// the expression `gBuffer[someIndex]` will be lowered to
+// a value that references `RWStructureBuffer<Foo>::operator[]`
+// with arguments `(gBuffer, someIndex)`.
+//
+// Such a value can be an l-value, and depending on the context
+// where it is used, can lower into a call to either the getter
+// or setter operations of the subscript.
+//
+struct BoundSubscriptInfo : ExtendedValueInfo
 {
     DeclRef<SubscriptDecl>  declRef;
     IRType*                 type;
     List<IRValue*>          args;
 };
 
+// Some cases of `ExtendedValueInfo` need to
+// recursively contain `LoweredValInfo`s, and
+// so we forward declare them here and fill
+// them in later.
+//
+struct BoundMemberInfo;
+struct SwizzledLValueInfo;
+
+
+// This type is our core representation of lowered values.
+// In the simple case, it just wraps an `IRInst*`.
+// More complex cases, representing l-values or aggregate
+// values are also supported.
 struct LoweredValInfo
 {
+    // Which of the cases of value are we looking at?
     enum class Flavor
     {
+        // No value (akin to a null pointer)
         None,
+
+        // A simple IR value
         Simple,
+
+        // An l-value reprsented as an IR
+        // pointer to the value
         Ptr,
+
+        // A member declaration bound to a particular `this` value
         BoundMember,
+
+        // A reference to an AST-level subscript operation
         Subscript,
+
+        // An AST-level subscript operation bound to a particular
+        // object and arguments.
         BoundSubscript,
+
+        // The result of applying swizzling to an l-value
+        SwizzledLValue,
     };
 
     union
     {
         IRValue*            val;
-        BoundMemberInfo*    boundMemberInfo;
-        SubscriptInfo*      subscriptInfo;
-        BoundSubscriptInfo* boundSubscriptInfo;
+        ExtendedValueInfo*  ext;
     };
     Flavor flavor;
 
@@ -66,33 +152,87 @@ struct LoweredValInfo
     }
 
     static LoweredValInfo boundMember(
-        LoweredValInfo const& base,
-        LoweredValInfo const& member);
+        BoundMemberInfo*    boundMemberInfo);
+
+    BoundMemberInfo* getBoundMemberInfo()
+    {
+        assert(flavor == Flavor::BoundMember);
+        return (BoundMemberInfo*)ext;
+    }
 
     static LoweredValInfo subscript(
         SubscriptInfo* subscriptInfo);
 
+    SubscriptInfo* getSubscriptInfo()
+    {
+        assert(flavor == Flavor::Subscript);
+        return (SubscriptInfo*)ext;
+    }
+
     static LoweredValInfo boundSubscript(
         BoundSubscriptInfo* boundSubscriptInfo);
+
+    BoundSubscriptInfo* getBoundSubscriptInfo()
+    {
+        assert(flavor == Flavor::BoundSubscript);
+        return (BoundSubscriptInfo*)ext;
+    }
+
+    static LoweredValInfo swizzledLValue(
+        SwizzledLValueInfo* extInfo);
+
+    SwizzledLValueInfo* getSwizzledLValueInfo()
+    {
+        assert(flavor == Flavor::SwizzledLValue);
+        return (SwizzledLValueInfo*)ext;
+    }
 };
 
-struct BoundMemberInfo
+// Represents some declaration bound to a particular
+// object. For example, if we had `obj.f` where `f`
+// is a member function, we'd use a `BoundMemberInfo`
+// to represnet this.
+//
+// Note: This case is largely avoided by special-casing
+// in the handling of calls (like `obj.f(arg)`), but
+// it is being left here as an example of what we might
+// need/want to do in the long term.
+struct BoundMemberInfo : ExtendedValueInfo
 {
+    // The base object
     LoweredValInfo  base;
-    LoweredValInfo  member;
+
+    // The (AST-level) declaration reference.
+    DeclRef<Decl> declRef;
 };
 
-LoweredValInfo LoweredValInfo::boundMember(
-    LoweredValInfo const& base,
-    LoweredValInfo const& member)
+// Represents the result of a swizzle operation in
+// an l-value context. A swizzle without duplicate
+// elements is allowed as an l-value, even if the
+// element are non-contiguous (`.xz`) or out of
+// order (`.zxy`).
+//
+struct SwizzledLValueInfo : ExtendedValueInfo
 {
-    BoundMemberInfo* boundMember = new BoundMemberInfo();
-    boundMember->base = base;
-    boundMember->member = member;
+    // IR-level The type of the expression.
+    IRType*         type;
+
+    // The base expression (this should be an l-value)
+    LoweredValInfo  base;
+
+    // The number of elements in the swizzle
+    UInt            elementCount;
 
+    // THe indices for the elements being swizzled
+    UInt            elementIndices[4];
+};
+
+LoweredValInfo LoweredValInfo::boundMember(
+    BoundMemberInfo*    boundMemberInfo)
+{
     LoweredValInfo info;
     info.flavor = Flavor::BoundMember;
-    info.boundMemberInfo = boundMember;
+    info.ext = boundMemberInfo;
     return info;
 }
 
@@ -101,7 +241,7 @@ LoweredValInfo LoweredValInfo::subscript(
 {
     LoweredValInfo info;
     info.flavor = Flavor::Subscript;
-    info.subscriptInfo = subscriptInfo;
+    info.ext = subscriptInfo;
     return info;
 }
 
@@ -110,10 +250,18 @@ LoweredValInfo LoweredValInfo::boundSubscript(
 {
     LoweredValInfo info;
     info.flavor = Flavor::BoundSubscript;
-    info.boundSubscriptInfo = boundSubscriptInfo;
+    info.ext = boundSubscriptInfo;
     return info;
 }
 
+LoweredValInfo LoweredValInfo::swizzledLValue(
+        SwizzledLValueInfo* extInfo)
+{
+    LoweredValInfo info;
+    info.flavor = Flavor::SwizzledLValue;
+    info.ext = extInfo;
+    return info;
+}
 
 struct SharedIRGenContext
 {
@@ -123,8 +271,13 @@ struct SharedIRGenContext
 
     Dictionary<DeclRef<Decl>, LoweredValInfo> declValues;
 
-    // Arrays we keep around strictly for memory-management purposes
-    List<RefPtr<BoundSubscriptInfo>> boundSubscripts;
+    // Arrays we keep around strictly for memory-management purposes:
+
+    // Any extended values created during lowering need
+    // to be cleaned up after the fact. We don't try
+    // to reference-count these along the way because
+    // they need to get stored into a `union` inside `LoweredValInfo`
+    List<RefPtr<ExtendedValueInfo>> extValues;
 };
 
 
@@ -178,6 +331,29 @@ LoweredValInfo emitCallToVal(
     }
 }
 
+LoweredValInfo emitCompoundAssignOp(
+    IRGenContext*   context,
+    IRType*         type,
+    IROp            op,
+    UInt            argCount,
+    IRValue* const* args)
+{
+    auto builder = context->irBuilder;
+
+    assert(argCount == 2);
+    auto leftPtr = args[0];
+    auto rightVal = args[1];
+
+    auto leftVal = builder->emitLoad(leftPtr);
+
+    IRInst* innerArgs[] = { leftVal, rightVal };
+    auto innerOp = builder->emitIntrinsicInst(type, op, 2, innerArgs);
+
+    builder->emitStore(leftPtr, innerOp);
+
+    return LoweredValInfo::ptr(leftPtr);
+}
+
 // Given a `DeclRef` for something callable, along with a bunch of
 // arguments, emit an appropriate call to it.
 LoweredValInfo emitCallToDeclRef(
@@ -229,7 +405,7 @@ LoweredValInfo emitCallToDeclRef(
             boundSubscript->type = type;
             boundSubscript->args.AddRange(args, argCount);
 
-            context->shared->boundSubscripts.Add(boundSubscript);
+            context->shared->extValues.Add(boundSubscript);
 
             return LoweredValInfo::boundSubscript(boundSubscript);
         }
@@ -245,6 +421,35 @@ LoweredValInfo emitCallToDeclRef(
     {
         auto op = getIntrinsicOp(funcDecl, intrinsicOpModifier);
 
+        if (Int(op) < 0)
+        {
+            switch (op)
+            {
+            case kIRPseudoOp_Pos:
+                return LoweredValInfo::simple(args[0]);
+
+#define CASE(COMPOUND, OP)  \
+            case COMPOUND: return emitCompoundAssignOp(context, type, OP, argCount, args)
+
+            CASE(kIRPseudoOp_AddAssign, kIROp_Add);
+            CASE(kIRPseudoOp_SubAssign, kIROp_Sub);
+            CASE(kIRPseudoOp_MulAssign, kIROp_Mul);
+            CASE(kIRPseudoOp_DivAssign, kIROp_Div);
+            CASE(kIRPseudoOp_ModAssign, kIROp_Mod);
+            CASE(kIRPseudoOp_AndAssign, kIROp_BitAnd);
+            CASE(kIRPseudoOp_OrAssign, kIROp_BitOr);
+            CASE(kIRPseudoOp_XorAssign, kIROp_BitXor);
+            CASE(kIRPseudoOp_LshAssign, kIROp_Lsh);
+            CASE(kIRPseudoOp_RshAssign, kIROp_Rsh);
+
+#undef CASE
+
+            default:
+                SLANG_UNIMPLEMENTED_X("IR pseudo-op");
+                break;
+            }
+        }
+
         return LoweredValInfo::simple(builder->emitIntrinsicInst(
             type,
             op,
@@ -277,6 +482,8 @@ LoweredValInfo emitCallToDeclRef(
 
 IRValue* getSimpleVal(IRGenContext* context, LoweredValInfo lowered)
 {
+    auto builder = context->irBuilder;
+
 top:
     switch(lowered.flavor)
     {
@@ -287,12 +494,11 @@ top:
         return lowered.val;
 
     case LoweredValInfo::Flavor::Ptr:
-        return context->irBuilder->emitLoad(lowered.val);
+        return builder->emitLoad(lowered.val);
 
     case LoweredValInfo::Flavor::BoundSubscript:
         {
-            auto boundSubscriptInfo = lowered.boundSubscriptInfo;
-            auto builder = context->irBuilder;
+            auto boundSubscriptInfo = lowered.getBoundSubscriptInfo();
 
             for (auto getter : getMembersOfType<GetterDecl>(boundSubscriptInfo->declRef))
             {
@@ -309,6 +515,17 @@ top:
         }
         break;
 
+    case LoweredValInfo::Flavor::SwizzledLValue:
+        {
+            auto swizzleInfo = lowered.getSwizzledLValueInfo();
+            
+            return builder->emitSwizzle(
+                swizzleInfo->type,
+                getSimpleVal(context, swizzleInfo->base),
+                swizzleInfo->elementCount,
+                swizzleInfo->elementIndices);
+        }
+
     default:
         SLANG_UNEXPECTED("unhandled value flavor");
         return nullptr;
@@ -397,8 +614,11 @@ IRType* lowerSimpleType(
     return getSimpleType(lowered);
 }
 
+LoweredValInfo lowerLValueExpr(
+    IRGenContext*   context,
+    Expr*           expr);
 
-LoweredValInfo lowerExpr(
+LoweredValInfo lowerRValueExpr(
     IRGenContext*   context,
     Expr*           expr);
 
@@ -528,6 +748,38 @@ struct ValLoweringVisitor : ValVisitor<ValLoweringVisitor, LoweredValInfo, Lower
 
         return getBuilder()->getMatrixType(irElementType, irRowCount, irColumnCount);
     }
+
+    LoweredTypeInfo getArrayType(
+        LoweredTypeInfo const&  loweredElementType,
+        IRValue*                irElementCount)
+    {
+        switch (loweredElementType.flavor)
+        {
+        case LoweredTypeInfo::Flavor::Simple:
+            return getBuilder()->getArrayType(
+                loweredElementType.type,
+                irElementCount);
+            break;
+
+        default:
+            SLANG_UNEXPECTED("array element type");
+            break;
+        }
+    }
+
+    LoweredTypeInfo visitArrayExpressionType(ArrayExpressionType* type)
+    {
+        auto loweredElementType = lowerType(context, type->BaseType);
+        if (auto elementCount = type->ArrayLength)
+        {
+            auto irElementCount = lowerSimpleVal(context, elementCount);
+            return getArrayType(loweredElementType, irElementCount);
+        }
+        else
+        {
+            return getArrayType(loweredElementType, nullptr);
+        }
+    }
 };
 
 LoweredValInfo lowerVal(
@@ -556,15 +808,79 @@ struct LoweringVisitor
     , ValVisitor<LoweringVisitor, RefPtr<Val>, RefPtr<Type>>
 #endif
 
+LoweredValInfo createVar(
+    IRGenContext*   context,
+    LoweredTypeInfo type,
+    Decl*           decl = nullptr,
+    Layout*         layout = nullptr,
+    IRAddressSpace  addressSpace = kIRAddressSpace_Default)
+{
+    auto builder = context->irBuilder;
+    switch( type.flavor )
+    {
+    case LoweredTypeInfo::Flavor::Simple:
+        {
+            auto irAlloc = builder->emitVar(getSimpleType(type), addressSpace);
+
+            if (decl)
+            {
+                builder->addHighLevelDeclDecoration(irAlloc, decl);
+            }
+
+            if (layout)
+            {
+                builder->addLayoutDecoration(irAlloc, layout);
+            }
+
+
+            return LoweredValInfo::ptr(irAlloc);
+        }
+        break;
+
+    default:
+        SLANG_UNIMPLEMENTED_X("var type");
+        return LoweredValInfo();
+    }
+
+}
+
+void addArgs(
+    IRGenContext*   context,
+    List<IRValue*>* ioArgs,
+    LoweredValInfo  argInfo)
+{
+    auto& args = *ioArgs;
+    switch( argInfo.flavor )
+    {
+    case LoweredValInfo::Flavor::Simple:
+    case LoweredValInfo::Flavor::Ptr:
+    case LoweredValInfo::Flavor::SwizzledLValue:
+        args.Add(getSimpleVal(context, argInfo));
+        break;
+
+    default:
+        SLANG_UNIMPLEMENTED_X("addArgs case");
+        break;
+    }
+}
 
 //
 
-struct ExprLoweringVisitor : ExprVisitor<ExprLoweringVisitor, LoweredValInfo>
+template<typename Derived>
+struct ExprLoweringVisitorBase : ExprVisitor<Derived, LoweredValInfo>
 {
     IRGenContext* context;
 
     IRBuilder* getBuilder() { return context->irBuilder; }
 
+    // Lower an expression that should have the same l-value-ness
+    // as the visitor itself.
+    LoweredValInfo lowerSubExpr(Expr* expr)
+    {
+        return dispatch(expr);
+    }
+
+
     LoweredValInfo visitVarExpr(VarExpr* expr)
     {
         LoweredValInfo info = ensureDecl(context, expr->declRef);
@@ -576,6 +892,83 @@ struct ExprLoweringVisitor : ExprVisitor<ExprLoweringVisitor, LoweredValInfo>
         SLANG_UNEXPECTED("overloaded expressions should not occur in checked AST");
     }
 
+    LoweredValInfo visitIndexExpr(IndexExpr* expr)
+    {
+        auto type = lowerType(context, expr->type);
+        auto baseVal = lowerSubExpr(expr->BaseExpression);
+        auto indexVal = getSimpleVal(context, lowerRValueExpr(context, expr->IndexExpression));
+
+        return subscriptValue(type, baseVal, indexVal);
+    }
+
+    LoweredValInfo visitMemberExpr(MemberExpr* expr)
+    {
+        auto loweredType = lowerType(context, expr->type);
+        auto loweredBase = lowerRValueExpr(context, expr->BaseExpression);
+
+        auto declRef = expr->declRef;
+        if (auto fieldDeclRef = declRef.As<StructField>())
+        {
+            // Okay, easy enough: we have a reference to a field of a struct type...
+
+            auto loweredField = ensureDecl(context, fieldDeclRef);
+            return extractField(loweredType, loweredBase, loweredField);
+        }
+        else if (auto callableDeclRef = declRef.As<CallableDecl>())
+        {
+            RefPtr<BoundMemberInfo> boundMemberInfo = new BoundMemberInfo();
+            boundMemberInfo->base = loweredBase;
+            boundMemberInfo->declRef = callableDeclRef;
+            return LoweredValInfo::boundMember(boundMemberInfo);
+        }
+
+        SLANG_UNIMPLEMENTED_X("codegen for subscript expression");
+    }
+
+    // We will always lower a dereference expression (`*ptr`)
+    // as an l-value, since that is the easiest way to handle it.
+    LoweredValInfo visitDerefExpr(DerefExpr* expr)
+    {
+        auto loweredType = lowerType(context, expr->type);
+        auto loweredBase = lowerRValueExpr(context, expr->base);
+
+        // TODO: handle tupel-type for `base`
+
+        // The type of the lowered base must by some kind of pointer,
+        // in order for a dereference to make senese, so we just
+        // need to extract the value type from that pointer here.
+        //
+        auto loweredBaseVal = getSimpleVal(context, loweredBase);
+        auto loweredBaseType = loweredBaseVal->getType();
+        switch( loweredBaseType->op )
+        {
+        case kIROp_PtrType:
+        // TODO: should we enumerate these explicitly?
+        case kIROp_ConstantBufferType:
+        case kIROp_TextureBufferType:
+            // Note that we do *not* perform an actual `load` operation
+            // here, but rather just use the pointer value to construct
+            // an appropriate `LoweredValInfo` representing the underlying
+            // dereference.
+            //
+            // This is important so that an expression like `&((*foo).bar)`
+            // (which is desugared from `&foo->bar`) can be handled; such
+            // an expression does *not* perform a dereference at runtime,
+            // and is just a bit of pointer math.
+            //
+            return LoweredValInfo::ptr(loweredBaseVal);
+
+        default:
+            SLANG_UNIMPLEMENTED_X("codegen for deref expression");
+            return LoweredValInfo();
+        }
+    }
+
+    LoweredValInfo visitParenExpr(ParenExpr* expr)
+    {
+        return lowerSubExpr(expr->base);
+    }
+
     LoweredValInfo visitInitializerListExpr(InitializerListExpr* expr)
     {
         SLANG_UNIMPLEMENTED_X("codegen for initializer list expression");
@@ -605,23 +998,6 @@ struct ExprLoweringVisitor : ExprVisitor<ExprLoweringVisitor, LoweredValInfo>
         SLANG_UNIMPLEMENTED_X("codegen for aggregate type constructor expression");
     }
 
-    void addArgs(List<IRValue*>* ioArgs, LoweredValInfo argInfo)
-    {
-        auto& args = *ioArgs;
-        switch( argInfo.flavor )
-        {
-        case LoweredValInfo::Flavor::Simple:
-        case LoweredValInfo::Flavor::Ptr:
-            args.Add(getSimpleVal(context, argInfo));
-            break;
-
-        default:
-            SLANG_UNIMPLEMENTED_X("addArgs case");
-            break;
-        }
-    }
-
-
     // Add arguments that appeared directly in an argument list
     // to the list of argument values for a call.
     void addDirectCallArgs(
@@ -632,45 +1008,129 @@ struct ExprLoweringVisitor : ExprVisitor<ExprLoweringVisitor, LoweredValInfo>
 
         for( auto arg : expr->Arguments )
         {
-            auto loweredArg = lowerExpr(context, arg);
-            addArgs(&irArgs, loweredArg);
+            // TODO: Need to handle case of l-value arguments,
+            // when they are matched to `out` or `in out` parameters.
+            auto loweredArg = lowerRValueExpr(context, arg);
+            addArgs(context, ioArgs, loweredArg);
         }
     }
 
-    // Try to add "all" the arguments for a call to the argument list,
-    // including implicit arguments that come from (e.g.,) a member
-    // expression used to form the call.
-    void addCallArgs(
-        InvokeExpr*     expr,
-        List<IRValue*>* ioArgs)
-    {
-        auto& irArgs = *ioArgs;
+    // After a call to a function with `out` or `in out`
+    // parameters, we may need to copy data back into
+    // the l-value locations used for output arguments.
+    //
+    // During lowering of the argument list, we build
+    // up a list of these "fixup" assignments that need
+    // to be performed.
+    struct OutArgumentFixup
+    {
+        LoweredValInfo dst;
+        LoweredValInfo src;
+    };
 
-        // TODO: should unwrap any layers of identity expressions around this...
-        if( auto baseMemberExpr = expr->FunctionExpr.As<MemberExpr>() )
+    void addDirectCallArgs(
+        InvokeExpr*             expr,
+        DeclRef<CallableDecl>   funcDeclRef,
+        List<IRValue*>*         ioArgs,
+        List<OutArgumentFixup>* ioFixups)
+    {
+        auto funcDecl = funcDeclRef.getDecl();
+        auto& args = expr->Arguments;
+        UInt argCount = expr->Arguments.Count();
+        UInt argIndex = 0;
+        for (auto paramDeclRef : getMembersOfType<ParamDecl>(funcDeclRef))
         {
-            // This call took the form of a member function call, so
-            // we need to correctly add the `this` argument as
-            // an explicit argument.
-            //
-            auto loweredBase = lowerExpr(context, baseMemberExpr->BaseExpression);
-            addArgs(&irArgs, loweredBase);
-        }
+            if (argIndex >= argCount)
+            {
+                // The remaining parameters must be defaulted...
+                break;
+            }
 
-        addDirectCallArgs(expr, ioArgs);
-    }
+            auto paramDecl = paramDeclRef.getDecl();
+            auto paramType = lowerType(context, GetType(paramDeclRef));
+            auto argExpr = expr->Arguments[argIndex++];
 
-    LoweredValInfo lowerIntrinsicCall(
-        InvokeExpr* expr,
-        IROp intrinsicOp)
-    {
-        auto type = lowerSimpleType(context, expr->type);
+            if (paramDecl->HasModifier<OutModifier>()
+                || paramDecl->HasModifier<InOutModifier>())
+            {
+                // This is a `out` or `inout` parameter, and so
+                // the argument must be lowered as an l-value.
+
+                LoweredValInfo loweredArg = lowerLValueExpr(context, argExpr);
+
+                // According to our "calling convention" we need to
+                // pass a pointer into the callee.
+                //
+                // A naive approach would be to just take the address
+                // of `loweredArg` above and pass it in, but that
+                // has two issues:
+                //
+                // 1. The l-value might not be something that has a single
+                //    well-defined "address" (e.g., `foo.xzy`).
+                //
+                // 2. The l-value argument might actually alias some other
+                //    storage that the callee will access (e.g., we are
+                //    passing in a global variable, or two `out` parameters
+                //    are being passed the same location in an array).
+                //
+                // In each of these cases, the safe option is to create
+                // a temporary variable to use for argument-passing,
+                // and then do copy-in/copy-out around the call.
+
+                LoweredValInfo tempVar = createVar(context, paramType);
+
+                // If the parameter is `in out` or `inout`, then we need
+                // to ensure that we pass in the original value stored
+                // in the argument, which we accomplish by assigning
+                // from the l-value to our temp.
+                if (paramDecl->HasModifier<InModifier>()
+                    || paramDecl->HasModifier<InOutModifier>())
+                {
+                    assign(context, tempVar, loweredArg);
+                }
 
-        List<IRValue*>  irArgs;
-        addCallArgs(expr, &irArgs);
-        UInt argCount = irArgs.Count();
+                // Now we can pass the address of the temporary variable
+                // to the callee as the actual argument for the `in out`
+                assert(tempVar.flavor == LoweredValInfo::Flavor::Ptr);
+                (*ioArgs).Add(tempVar.val);
 
-        return LoweredValInfo::simple(getBuilder()->emitIntrinsicInst(type, intrinsicOp, argCount, &irArgs[0]));
+                // Finally, after the call we will need
+                // to copy in the other direction: from our
+                // temp back to the original l-value.
+                OutArgumentFixup fixup;
+                fixup.src = tempVar;
+                fixup.dst = loweredArg;
+
+                (*ioFixups).Add(fixup);
+
+            }
+            else
+            {
+                // This is a pure input parameter, and so we will
+                // pass it as an r-value.
+                LoweredValInfo loweredArg = lowerRValueExpr(context, argExpr);
+                addArgs(context, ioArgs, loweredArg);
+            }
+        }
+    }
+
+    // Add arguments that appeared directly in an argument list
+    // to the list of argument values for a call.
+    void addDirectCallArgs(
+        InvokeExpr*             expr,
+        DeclRef<Decl>           funcDeclRef,
+        List<IRValue*>*         ioArgs,
+        List<OutArgumentFixup>* ioFixups)
+    {
+        if (auto callableDeclRef = funcDeclRef.As<CallableDecl>())
+        {
+            addDirectCallArgs(expr, callableDeclRef, ioArgs, ioFixups);
+        }
+        else
+        {
+            SLANG_UNEXPECTED("shouldn't relaly happen");
+            addDirectCallArgs(expr, ioArgs);
+        }
     }
 
     void addFuncBaseArgs(
@@ -684,9 +1144,12 @@ struct ExprLoweringVisitor : ExprVisitor<ExprLoweringVisitor, LoweredValInfo>
         }
     }
 
-    LoweredValInfo lowerSimpleCall(InvokeExpr* expr)
+    void applyOutArgumentFixups(List<OutArgumentFixup> const& fixups)
     {
-
+        for (auto fixup : fixups)
+        {
+            assign(context, fixup.dst, fixup.src);
+        }
     }
 
     LoweredValInfo visitInvokeExpr(InvokeExpr* expr)
@@ -711,40 +1174,60 @@ struct ExprLoweringVisitor : ExprVisitor<ExprLoweringVisitor, LoweredValInfo>
         // arguments that will be part of the call.
         List<IRValue*> irArgs;
 
+        // We will also collect "fixup" actions that need
+        // to be performed after teh call, in order to
+        // copy the final values for `out` parameters
+        // back to their arguments.
+        List<OutArgumentFixup> argFixups;
 
         auto funcExpr = expr->FunctionExpr;
         if (auto memberFuncExpr = funcExpr.As<MemberExpr>())
         {
-            auto loweredBaseVal = lowerExpr(context, memberFuncExpr->BaseExpression);
-            addArgs(&irArgs, loweredBaseVal);
+            auto loweredBaseVal = lowerRValueExpr(context, memberFuncExpr->BaseExpression);
+            addArgs(context, &irArgs, loweredBaseVal);
 
             auto funcDeclRef = memberFuncExpr->declRef;
 
-            addDirectCallArgs(expr, &irArgs);
-            return emitCallToDeclRef(context, type, funcDeclRef, irArgs);
+            addDirectCallArgs(expr, funcDeclRef, &irArgs, &argFixups);
+            auto result = emitCallToDeclRef(context, type, funcDeclRef, irArgs);
+            applyOutArgumentFixups(argFixups);
+            return result;
         }
         else if (auto staticMemberFuncExpr = funcExpr.As<StaticMemberExpr>())
         {
             auto funcDeclRef = staticMemberFuncExpr->declRef;
-            addDirectCallArgs(expr, &irArgs);
-            return emitCallToDeclRef(context, type, funcDeclRef, irArgs);
+            addDirectCallArgs(expr, funcDeclRef, &irArgs, &argFixups);
+            auto result = emitCallToDeclRef(context, type, funcDeclRef, irArgs);
+            applyOutArgumentFixups(argFixups);
+            return result;
         }
         else if (auto varExpr = funcExpr.As<VarExpr>())
         {
             auto funcDeclRef = varExpr->declRef;
-            addDirectCallArgs(expr, &irArgs);
-            return emitCallToDeclRef(context, type, funcDeclRef, irArgs);
+            addDirectCallArgs(expr, funcDeclRef, &irArgs, &argFixups);
+            auto result = emitCallToDeclRef(context, type, funcDeclRef, irArgs);
+            applyOutArgumentFixups(argFixups);
+            return result;
         }
 
         // The default case is to assume that we just have
         // an ordinary expression, and can lower it as such.
-        LoweredValInfo funcVal = lowerExpr(context, expr->FunctionExpr);
+        LoweredValInfo funcVal = lowerRValueExpr(context, expr->FunctionExpr);
 
         // Now we add any direct arguments from the call expression itself.
         addDirectCallArgs(expr, &irArgs);
 
         // Delegate to the logic for invoking a value.
-        return emitCallToVal(context, type, funcVal, irArgs.Count(), irArgs.Buffer());
+        auto result = emitCallToVal(context, type, funcVal, irArgs.Count(), irArgs.Buffer());
+
+        // TODO: because of the nature of how the `emitCallToVal` case works
+        // right now, we don't have information on in/out parameters, and
+        // so we can't collect info to apply fixups.
+        //
+        // Once we have a better representation for function types, though,
+        // this should be fixable.
+
+        return result;
     }
 
     LoweredValInfo subscriptValue(
@@ -776,15 +1259,6 @@ struct ExprLoweringVisitor : ExprVisitor<ExprLoweringVisitor, LoweredValInfo>
 
     }
 
-    LoweredValInfo visitIndexExpr(IndexExpr* expr)
-    {
-        auto type = lowerType(context, expr->type);
-        auto baseVal = lowerExpr(context, expr->BaseExpression);
-        auto indexVal = getSimpleVal(context, lowerExpr(context, expr->IndexExpression));
-
-        return subscriptValue(type, baseVal, indexVal);
-    }
-
     LoweredValInfo extractField(
         LoweredTypeInfo fieldType,
         LoweredValInfo  base,
@@ -824,70 +1298,6 @@ struct ExprLoweringVisitor : ExprVisitor<ExprLoweringVisitor, LoweredValInfo>
         return ensureDecl(context, expr->declRef);
     }
 
-    LoweredValInfo visitMemberExpr(MemberExpr* expr)
-    {
-        auto loweredType = lowerType(context, expr->type);
-        auto loweredBase = lowerExpr(context, expr->BaseExpression);
-
-        auto declRef = expr->declRef;
-        if (auto fieldDeclRef = declRef.As<StructField>())
-        {
-            // Okay, easy enough: we have a reference to a field of a struct type...
-
-            auto loweredField = ensureDecl(context, fieldDeclRef);
-            return extractField(loweredType, loweredBase, loweredField);
-        }
-        else if (auto callableDeclRef = declRef.As<CallableDecl>())
-        {
-            auto loweredFunc = ensureDecl(context, callableDeclRef);
-            return LoweredValInfo::boundMember(loweredBase, loweredFunc);
-        }
-
-        SLANG_UNIMPLEMENTED_X("codegen for subscript expression");
-    }
-
-    LoweredValInfo visitSwizzleExpr(SwizzleExpr* expr)
-    {
-        SLANG_UNIMPLEMENTED_X("codegen for swizzle expression");
-    }
-
-    LoweredValInfo visitDerefExpr(DerefExpr* expr)
-    {
-        auto loweredType = lowerType(context, expr->type);
-        auto loweredBase = lowerExpr(context, expr->base);
-
-        // TODO: handle tupel-type for `base`
-
-        // The type of the lowered base must by some kind of pointer,
-        // in order for a dereference to make senese, so we just
-        // need to extract the value type from that pointer here.
-        //
-        auto loweredBaseVal = getSimpleVal(context, loweredBase);
-        auto loweredBaseType = loweredBaseVal->getType();
-        switch( loweredBaseType->op )
-        {
-        case kIROp_PtrType:
-        // TODO: should we enumerate these explicitly?
-        case kIROp_ConstantBufferType:
-        case kIROp_TextureBufferType:
-            // Note that we do *not* perform an actual `load` operation
-            // here, but rather just use the pointer value to construct
-            // an appropriate `LoweredValInfo` representing the underlying
-            // dereference.
-            //
-            // This is important so that an expression like `&((*foo).bar)`
-            // (which is desugared from `&foo->bar`) can be handled; such
-            // an expression does *not* perform a dereference at runtime,
-            // and is just a bit of pointer math.
-            //
-            return LoweredValInfo::ptr(loweredBaseVal);
-
-        default:
-            SLANG_UNIMPLEMENTED_X("codegen for deref expression");
-            return LoweredValInfo();
-        }
-    }
-
     LoweredValInfo visitTypeCastExpr(TypeCastExpr* expr)
     {
         SLANG_UNIMPLEMENTED_X("codegen for type cast expression");
@@ -916,8 +1326,8 @@ struct ExprLoweringVisitor : ExprVisitor<ExprLoweringVisitor, LoweredValInfo>
         // and right-hand sides, and then peform an assignment
         // based on the resulting values.
         //
-        auto leftVal = lowerExpr(context, expr->left);
-        auto rightVal = lowerExpr(context, expr->right);
+        auto leftVal = lowerLValueExpr(context, expr->left);
+        auto rightVal = lowerRValueExpr(context, expr->right);
         assign(context, leftVal, rightVal);
 
         // The result value of the assignment expression is
@@ -925,18 +1335,80 @@ struct ExprLoweringVisitor : ExprVisitor<ExprLoweringVisitor, LoweredValInfo>
         // to be an l-value).
         return leftVal;
     }
+};
 
-    LoweredValInfo visitParenExpr(ParenExpr* expr)
+struct LValueExprLoweringVisitor : ExprLoweringVisitorBase<LValueExprLoweringVisitor>
+{
+    // When visiting a swizzle expression in an l-value context,
+    // we need to construct a "sizzled l-value."
+    LoweredValInfo visitSwizzleExpr(SwizzleExpr* expr)
     {
-        return lowerExpr(context, expr->base);
+        auto irType = lowerSimpleType(context, expr->type);
+        auto loweredBase = lowerRValueExpr(context, expr->base);
+
+        RefPtr<SwizzledLValueInfo> swizzledLValue = new SwizzledLValueInfo();
+        swizzledLValue->type = irType;
+        swizzledLValue->base = loweredBase;
+
+        UInt elementCount = (UInt)expr->elementCount;
+        swizzledLValue->elementCount = elementCount;
+        for (UInt ii = 0; ii < elementCount; ++ii)
+        {
+            swizzledLValue->elementIndices[ii] = (UInt) expr->elementIndices[ii];
+        }
+
+        context->shared->extValues.Add(swizzledLValue);
+        return LoweredValInfo::swizzledLValue(swizzledLValue);
+    }
+
+};
+
+struct RValueExprLoweringVisitor : ExprLoweringVisitorBase<RValueExprLoweringVisitor>
+{
+    // A swizzle in an r-value context can save time by just
+    // emitting the swizzle instuctions directly.
+    LoweredValInfo visitSwizzleExpr(SwizzleExpr* expr)
+    {
+        auto irType = lowerSimpleType(context, expr->type);
+        auto irBase = getSimpleVal(context, lowerRValueExpr(context, expr->base));
+
+        auto builder = getBuilder();
+
+        auto irIntType = builder->getBaseType(BaseType::Int);
+
+        UInt elementCount = (UInt)expr->elementCount;
+        IRValue* irElementIndices[4];
+        for (UInt ii = 0; ii < elementCount; ++ii)
+        {
+            irElementIndices[ii] = builder->getIntValue(
+                irIntType,
+                (IRIntegerValue)expr->elementIndices[ii]);
+        }
+
+        auto irSwizzle = builder->emitSwizzle(
+            irType,
+            irBase,
+            elementCount,
+            &irElementIndices[0]);
+
+        return LoweredValInfo::simple(irSwizzle);
     }
 };
 
-LoweredValInfo lowerExpr(
+LoweredValInfo lowerLValueExpr(
+    IRGenContext*   context,
+    Expr*           expr)
+{
+    LValueExprLoweringVisitor visitor;
+    visitor.context = context;
+    return visitor.dispatch(expr);
+}
+
+LoweredValInfo lowerRValueExpr(
     IRGenContext*   context,
     Expr*           expr)
 {
-    ExprLoweringVisitor visitor;
+    RValueExprLoweringVisitor visitor;
     visitor.context = context;
     return visitor.dispatch(expr);
 }
@@ -952,6 +1424,185 @@ struct StmtLoweringVisitor : StmtVisitor<StmtLoweringVisitor>
         SLANG_UNIMPLEMENTED_X("stmt catch-all");
     }
 
+    // Create a basic block in the current function,
+    // so that it can be used for a label.
+    IRBlock* createBlock()
+    {
+        return getBuilder()->createBlock();
+    }
+
+    // Insert a block at the current location (ending
+    // the previous block with an unconditional jump
+    // if needed).
+    void insertBlock(IRBlock* block)
+    {
+        auto builder = getBuilder();
+        auto parent = builder->parentInst;
+
+        IRBlock* prevBlock = nullptr;
+        IRFunc* parentFunc = nullptr;
+
+        switch (parent->op)
+        {
+        case kIROp_Block:
+            prevBlock = (IRBlock*)parent;
+            parentFunc = prevBlock->getParent();
+            break;
+
+        default:
+            SLANG_UNEXPECTED("bad parent kind for block");
+            return;
+        }
+
+        // If the previous block doesn't already have
+        // a terminator instruction, then be sure to
+        // emit a branch to the new block.
+        if (!isTerminatorInst(prevBlock->lastChild))
+        {
+            builder->emitBranch(block);
+        }
+
+        builder->parentInst = parentFunc;
+        builder->addInst(block);
+        builder->parentInst = block;
+    }
+
+    // Start a new block at the current location.
+    // This is just the composition of `createBlock`
+    // and `insertBlock`.
+    IRBlock* startBlock()
+    {
+        auto block = createBlock();
+        insertBlock(block);
+        return block;
+    }
+
+    void visitIfStmt(IfStmt* stmt)
+    {
+        auto builder = getBuilder();
+
+        auto condExpr = stmt->Predicate;
+        auto thenStmt = stmt->PositiveStatement;
+        auto elseStmt = stmt->NegativeStatement;
+
+        auto irCond = getSimpleVal(context,
+            lowerRValueExpr(context, condExpr));
+
+        if (elseStmt)
+        {
+            auto thenBlock = createBlock();
+            auto elseBlock = createBlock();
+            auto afterBlock = createBlock();
+
+            builder->emitIfElse(irCond, thenBlock, elseBlock, afterBlock);
+
+            insertBlock(thenBlock);
+            lowerStmt(context, thenStmt);
+            builder->emitBranch(afterBlock);
+
+            insertBlock(elseBlock);
+            lowerStmt(context, elseStmt);
+
+            insertBlock(afterBlock);
+        }
+        else
+        {
+            auto thenBlock = createBlock();
+            auto afterBlock = createBlock();
+
+            builder->emitIf(irCond, thenBlock, afterBlock);
+
+            insertBlock(thenBlock);
+            lowerStmt(context, thenStmt);
+
+            insertBlock(afterBlock);
+        }
+    }
+
+    void addLoopDecorations(
+        IRInst* inst,
+        Stmt*   stmt)
+    {
+        for(auto attr : stmt->GetModifiersOfType<HLSLUncheckedAttribute>())
+        {
+            // TODO: We should actually catch these attributes during
+            // semantic checking, so that they have a strongly-typed
+            // representation in the AST.
+            if(getText(attr->getName()) == "unroll")
+            {
+                auto decoration = getBuilder()->addDecoration<IRLoopControlDecoration>(inst);
+                decoration->mode = kIRLoopControl_Unroll;
+            }
+        }
+    }
+
+    void visitForStmt(ForStmt* stmt)
+    {
+        auto builder = getBuilder();
+
+        // The initializer clause for the statement
+        // can always safetly be emitted to the current block.
+        if (auto initStmt = stmt->InitialStatement)
+        {
+            lowerStmt(context, initStmt);
+        }
+
+        // We will create blocks for the various places
+        // we need to jump to inside the control flow,
+        // including the blocks that will be referenced
+        // by `continue` or `break` statements.
+        auto loopHead = createBlock();
+        auto bodyLabel = createBlock();
+        auto breakLabel = createBlock();
+        auto continueLabel = createBlock();
+
+        // TODO: register `loopHead` as the target for a
+        // `continue` statement.
+
+        // Emit the branch that will start out loop,
+        // and then insert the block for the head.
+
+        auto loopInst = builder->emitLoop(
+            loopHead,
+            breakLabel,
+            continueLabel);
+
+        addLoopDecorations(loopInst, stmt);
+
+        insertBlock(loopHead);
+
+        // Now that we are within the header block, we
+        // want to emit the expression for the loop condition:
+        if (auto condExpr = stmt->PredicateExpression)
+        {
+            auto irCondition = getSimpleVal(context,
+                lowerRValueExpr(context, stmt->PredicateExpression));
+
+            // Now we want to `break` if the loop condition is false.
+            builder->emitLoopTest(
+                irCondition,
+                bodyLabel,
+                breakLabel);
+        }
+
+        // Emit the body of the loop
+        insertBlock(bodyLabel);
+        lowerStmt(context, stmt->Statement);
+
+        // Insert the `continue` block
+        insertBlock(continueLabel);
+        if (auto incrExpr = stmt->SideEffectExpression)
+        {
+            lowerRValueExpr(context, incrExpr);
+        }
+
+        // At the end of the body we need to jump back to the top.
+        builder->emitBranch(loopHead);
+
+        // Finally we insert the label that a `break` will jump to
+        insertBlock(breakLabel);
+    }
+
     void visitExpressionStmt(ExpressionStmt* stmt)
     {
         // The statement evaluates an expression
@@ -960,7 +1611,11 @@ struct StmtLoweringVisitor : StmtVisitor<StmtLoweringVisitor>
         // lower the expression, and don't use
         // the result.
         //
-        lowerExpr(context, stmt->Expression);
+        // Note that we lower using the l-value path,
+        // so that an expression statement that names
+        // a location (but doesn't load from it)
+        // will not actually emit a load.
+        lowerLValueExpr(context, stmt->Expression);
     }
 
     void visitDeclStmt(DeclStmt* stmt)
@@ -1004,7 +1659,7 @@ struct StmtLoweringVisitor : StmtVisitor<StmtLoweringVisitor>
         // a value first, and then emit the resulting value.
         if( auto expr = stmt->Expression )
         {
-            auto loweredExpr = lowerExpr(context, expr);
+            auto loweredExpr = lowerRValueExpr(context, expr);
 
             getBuilder()->emitReturn(getSimpleVal(context, loweredExpr));
         }
@@ -1026,9 +1681,15 @@ void lowerStmt(
 
 void assign(
     IRGenContext*           context,
-    LoweredValInfo const&   left,
-    LoweredValInfo const&   right)
+    LoweredValInfo const&   inLeft,
+    LoweredValInfo const&   inRight)
 {
+    LoweredValInfo left = inLeft;
+    LoweredValInfo right = inRight;
+
+    auto builder = context->irBuilder;
+
+top:
     switch (left.flavor)
     {
     case LoweredValInfo::Flavor::Ptr:
@@ -1036,8 +1697,8 @@ void assign(
         {
         case LoweredValInfo::Flavor::Simple:
         case LoweredValInfo::Flavor::Ptr:
+        case LoweredValInfo::Flavor::SwizzledLValue:
             {
-                auto builder = context->irBuilder;
                 builder->emitStore(
                     left.val,
                     getSimpleVal(context, right));
@@ -1050,6 +1711,90 @@ void assign(
         }
         break;
 
+    case LoweredValInfo::Flavor::SwizzledLValue:
+        {
+            // The `left` value is of the form `<someLValue>.<swizzleElements>`.
+            //
+            // We could conceivably define a custom "swizzled store" instruction
+            // that would handle the common case where the base l-value is
+            // a simple lvalue (`LowerdValInfo::Flavor::Ptr`):
+            //
+            //     float4 foo;
+            //     foo.zxy = float3(...);
+            //
+            // However, this doesn't handle complex cases like the following:
+            //
+            //     RWStructureBuffer<float4> foo;
+            //     ...
+            //     foo[index].xzy = float3(...);
+            //
+            // In a case like that, we really need to lower through a temp:
+            //
+            //     float4 tmp = foo[index];
+            //     tmp.xzy = float3(...);
+            //     foo[index] = tmp;
+            //
+            // We want to handle the general case, we we might as well
+            // try to handle everything uniformly.
+            //
+            auto swizzleInfo = left.getSwizzledLValueInfo();
+            auto type = swizzleInfo->type;
+            auto loweredBase = swizzleInfo->base;
+
+            // Load from the base value:
+            IRInst* irLeftVal = getSimpleVal(context, loweredBase);
+            auto irRightVal = getSimpleVal(context, right);
+
+            // Now apply the swizzle
+            IRInst* irSwizzled = builder->emitSwizzleSet(
+                irLeftVal->getType(),
+                irLeftVal,
+                irRightVal,
+                swizzleInfo->elementCount,
+                swizzleInfo->elementIndices);
+
+            // And finally, store the value back where we got it.
+            //
+            // Note: this is effectively a recursive call to
+            // `assign()`, so we do a simple tail-recursive call here.
+            left = loweredBase;
+            right = LoweredValInfo::simple(irSwizzled);
+            goto top;
+        }
+        break;
+
+    case LoweredValInfo::Flavor::BoundSubscript:
+        {
+            // The `left` value refers to a subscript operation on
+            // a resource type, bound to particular arguments, e.g.:
+            // `someStructuredBuffer[index]`.
+            //
+            // When storing to such a value, we need to emit a call
+            // to the appropriate builtin "setter" accessor.
+            auto subscriptInfo = left.getBoundSubscriptInfo();
+            auto type = subscriptInfo->type;
+
+            // Search for an appropriate "setter" declaration
+            for (auto setterDeclRef : getMembersOfType<SetterDecl>(subscriptInfo->declRef))
+            {
+                auto allArgs = subscriptInfo->args;
+                
+                addArgs(context, &allArgs, right);
+
+                emitCallToDeclRef(
+                    context,
+                    builder->getVoidType(),
+                    setterDeclRef,
+                    allArgs);
+                return;
+            }
+
+            // No setter found? Then we have an error!
+            SLANG_UNEXPECTED("no setter found");
+            break;
+        }
+        break;
+
     default:
         SLANG_UNIMPLEMENTED_X("assignment");
         break;
@@ -1120,33 +1865,44 @@ struct DeclLoweringVisitor : DeclVisitor<DeclLoweringVisitor, LoweredValInfo>
 
         auto varType = lowerType(context, decl->getType());
 
-        LoweredValInfo varVal;
+        // TODO: If the variable is marked `static` then we need to
+        // deal with it specially: we should move its allocation out
+        // to the global scope, and then we have to deal with its
+        // initializer expression a bit carefully (it should only
+        // be initialized on-demand at its first use).
+
+        // Some qualifiers on a variable will change how we allocate it,
+        // so we need to reflect that somehow. The first example
+        // we run into is the `groupshared` qualifier, which marks
+        // a variable in a compute shader as having per-group allocation
+        // rather than the traditional per-thread (or rather per-thread
+        // per-activation-record) allocation.
+        //
+        // Options include:
+        //
+        //  - Use a distinct allocation opration, so that the type
+        //    of the variable address/value is unchanged.
+        //
+        //  - Add a notion of an "address space" to pointer types,
+        //    so that we can allocate things in distinct spaces.
+        //
+        //  - Add a notion of a "rate" so that we can declare a
+        //    variable with a distinct rate.
+        //
+        // For now we might do the expedient thing and handle this
+        // via a notion of an "address space."
 
-        switch( varType.flavor )
+        IRAddressSpace addressSpace = kIRAddressSpace_Default;
+        if (decl->HasModifier<HLSLGroupSharedModifier>())
         {
-        case LoweredTypeInfo::Flavor::Simple:
-            {
-                auto irAlloc = getBuilder()->emitVar(getSimpleType(varType));
-
-                getBuilder()->addHighLevelDeclDecoration(irAlloc, decl);
-
-                if (getLayout())
-                {
-                    getBuilder()->addLayoutDecoration(irAlloc, getLayout());
-                }
-
-
-                varVal = LoweredValInfo::ptr(irAlloc);
-            }
-            break;
-
-        default:
-            SLANG_UNIMPLEMENTED_X("struct field type");
+            addressSpace = kIRAddressSpace_GroupShared;
         }
 
+        LoweredValInfo varVal = createVar(context, varType, decl, getLayout(), addressSpace);
+
         if( auto initExpr = decl->initExpr )
         {
-            auto initVal = lowerExpr(context, initExpr);
+            auto initVal = lowerRValueExpr(context, initExpr);
 
             assign(context, varVal, initVal);
         }
@@ -1241,6 +1997,8 @@ struct DeclLoweringVisitor : DeclVisitor<DeclLoweringVisitor, LoweredValInfo>
 
             IRParam* irParam = subBuilder->emitParam(irParamType);
 
+            subBuilder->addHighLevelDeclDecoration(irParam, paramDecl);
+
             DeclRef<ParamDecl> paramDeclRef = makeDeclRef(paramDecl.Ptr());
 
             LoweredValInfo irParamVal = LoweredValInfo::simple(irParam);
@@ -1278,6 +2036,21 @@ struct DeclLoweringVisitor : DeclVisitor<DeclLoweringVisitor, LoweredValInfo>
 
         lowerStmt(subContext, decl->Body);
 
+        // We need to carefully add a terminator instruction to the end
+        // of the body, in case the user didn't do so.
+        if (!isTerminatorInst(subContext->irBuilder->parentInst->lastChild))
+        {
+            if (irResultType->op == kIROp_VoidType)
+            {
+                subContext->irBuilder->emitReturn();
+            }
+            else
+            {
+                SLANG_UNEXPECTED("Needed a return here");
+                subContext->irBuilder->emitReturn();
+            }
+        }
+
         getBuilder()->addHighLevelDeclDecoration(irFunc, decl);
 
         getBuilder()->addInst(irFunc);
@@ -1365,11 +2138,48 @@ static void lowerEntryPointToIR(
     EntryPointRequest*  entryPointRequest,
     EntryPointLayout*   entryPointLayout)
 {
-    auto entryPointFunc = entryPointLayout->entryPoint;
+    // First, lower the entry point like an ordinary function
+    auto entryPointFuncDecl = entryPointLayout->entryPoint;
+    auto loweredEntryPointFunc = lowerDecl(context, entryPointFuncDecl, entryPointLayout);
+    auto irFunc = getSimpleVal(context, loweredEntryPointFunc);
+
+    auto builder = context->irBuilder;
+
+    // We are going to attach all the entry-point-specific information
+    // to the declaration as meta-data decorations for now.
+    //
+    // I'm not convinced this is the right way to go, but it is
+    // the easiest and most expedient thing.
+    //
+    auto profile = entryPointRequest->profile;
+    auto stage = profile.GetStage();
 
-    // TODO: entry point lowering is probably *not* just like lowering a function...
+    auto entryPointDecoration = builder->addDecoration<IREntryPointDecoration>(irFunc);
+    entryPointDecoration->profile = profile;
 
-    lowerDecl(context, entryPointFunc, entryPointLayout);
+    // Next, we need to start attaching the meta-data that is
+    // required based on the particular stage we are targetting:
+    switch (stage)
+    {
+    case Stage::Compute:
+        {
+            // We need to attach information about the thread group size here.
+            auto threadGroupSizeDecoration = builder->addDecoration<IRComputeThreadGroupSizeDecoration>(irFunc);
+            static const UInt kAxisCount = 3;
+
+            // TODO: this is kind of gross because we are using a public
+            // reflection API function, rather than some kind of internal
+            // utility it forwards to...
+            spReflectionEntryPoint_getComputeThreadGroupSize(
+                (SlangReflectionEntryPoint*)entryPointLayout,
+                kAxisCount,
+                &threadGroupSizeDecoration->sizeAlongAxis[0]);
+        }
+        break;
+
+    default:
+        break;
+    }
 }
 
 IRModule* lowerEntryPointToIR(
@@ -1412,4 +2222,17 @@ IRModule* lowerEntryPointToIR(
 
 }
 
+String emitSlangIRAssemblyForEntryPoint(
+    EntryPointRequest*  entryPoint)
+{
+    auto compileRequest = entryPoint->compileRequest;
+    auto irModule = lowerEntryPointToIR(
+        entryPoint,
+        compileRequest->layout.Ptr(),
+        // TODO: we need to pick the target more carefully here
+        CodeGenTarget::HLSL);
+
+    return getSlangIRAssembly(irModule);
+}
+
 }
diff --git a/source/slang/options.cpp b/source/slang/options.cpp
index 669ab1827..a87692700 100644
--- a/source/slang/options.cpp
+++ b/source/slang/options.cpp
@@ -300,6 +300,8 @@ struct OptionsParser
 
                     CASE(spirv, SPIRV);
                     CASE(spirv-assembly, SPIRV_ASM);
+                    CASE(slang-ir, IR);
+                    CASE(slang-ir-assembly, IR_ASM);
                     CASE(none, TARGET_NONE);
 
                 #undef CASE
diff --git a/source/slang/profile-defs.h b/source/slang/profile-defs.h
index 84153ee46..513ba3078 100644
--- a/source/slang/profile-defs.h
+++ b/source/slang/profile-defs.h
@@ -47,6 +47,8 @@ LANGUAGE(GLSL_ES,			glsl_es)
 LANGUAGE(GLSL_VK,			glsl_vk)
 LANGUAGE(SPIRV,				spirv)
 LANGUAGE(SPIRV_GL,			spirv_gl)
+LANGUAGE(SlangIR,           slang_ir)
+LANGUAGE(SlangIRAssembly,   slang_ir_assembly)
 
 LANGUAGE_ALIAS(GLSL,		glsl_gl)
 LANGUAGE_ALIAS(SPIRV,		spirv_vk)
diff --git a/source/slang/slang.vcxproj b/source/slang/slang.vcxproj
index 1f55138e4..08a448a6d 100644
--- a/source/slang/slang.vcxproj
+++ b/source/slang/slang.vcxproj
@@ -172,6 +172,7 @@
     <ClInclude Include="emit.h" />
     <ClInclude Include="expr-defs.h" />
     <ClInclude Include="ir-inst-defs.h" />
+    <ClInclude Include="ir-insts.h" />
     <ClInclude Include="ir.h" />
     <ClInclude Include="lexer.h" />
     <ClInclude Include="lookup.h" />
diff --git a/source/slang/slang.vcxproj.filters b/source/slang/slang.vcxproj.filters
index 9a85ce966..111b23d36 100644
--- a/source/slang/slang.vcxproj.filters
+++ b/source/slang/slang.vcxproj.filters
@@ -39,6 +39,7 @@
     <ClInclude Include="ir.h" />
     <ClInclude Include="lower-to-ir.h" />
     <ClInclude Include="ir-inst-defs.h" />
+    <ClInclude Include="ir-insts.h" />
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="check.cpp" />
@@ -65,8 +66,8 @@
     <ClCompile Include="lower-to-ir.cpp" />
   </ItemGroup>
   <ItemGroup>
-    <None Include="core.meta.slang" />
-    <None Include="glsl.meta.slang" />
-    <None Include="hlsl.meta.slang" />
+    <CustomBuild Include="core.meta.slang" />
+    <CustomBuild Include="glsl.meta.slang" />
+    <CustomBuild Include="hlsl.meta.slang" />
   </ItemGroup>
 </Project>
\ No newline at end of file
diff --git a/source/slang/type-layout.cpp b/source/slang/type-layout.cpp
index 00a625427..ec71df37d 100644
--- a/source/slang/type-layout.cpp
+++ b/source/slang/type-layout.cpp
@@ -621,6 +621,8 @@ LayoutRulesFamilyImpl* GetLayoutRulesFamilyImpl(CodeGenTarget target)
     case CodeGenTarget::HLSL:
     case CodeGenTarget::DXBytecode:
     case CodeGenTarget::DXBytecodeAssembly:
+    case CodeGenTarget::SlangIR:
+    case CodeGenTarget::SlangIRAssembly:
         return &kHLSLLayoutRulesFamilyImpl;
 
     case CodeGenTarget::GLSL: