IR: support global variable with initializers (#294)

The big change here is that the ability to contain basic blocks with instructions in them has been hoisted from `IRFunc` into a new base type `IRGlobalValueWithCode` shared with `IRGlobalVar`.
The basic blocks of a global variable define initialization logic for it; they can be looked at like a function that returns the initial value.

Places in the IR that used to assume functions contain all the code need to be updated, but so far I only handled the cloning step.

The emit logic currently handles an initializer for a global variable by outputting its logic as a separate function, and then having the variable call that function to initialize itself. This should be cleaned up over time so that we generate an ordinary expression whenever possible.

I also made the emit logic correctly label any global variable without a layout (that is, any that don't represent a shader parameter) as `static` so that the downstream HLSL compiler sees them as variables rather than parameters.

1 files changed, 41 insertions, 11 deletions

diff --git a/source/slang/emit.cpp b/source/slang/emit.cpp
index 383442236..4cad7b28d 100644
--- a/source/slang/emit.cpp
+++ b/source/slang/emit.cpp
@@ -6461,7 +6461,23 @@ emitDeclImpl(decl, nullptr);
     {
         auto allocatedType = varDecl->getType();
         auto varType = allocatedType->getValueType();
-//        auto addressSpace = allocatedType->getAddressSpace();
+
+        String initFuncName;
+        if (varDecl->firstBlock)
+        {
+            // A global variable with code means it has an initializer
+            // associated with it. Eventually we'd like to emit that
+            // initializer directly as an expression here, but for
+            // now we'll emit it as a separate function.
+
+            initFuncName = getIRName(varDecl);
+            initFuncName.append("_init");
+            emitIRType(ctx, varType, initFuncName);
+            Emit("()\n{\n");
+            emitIRStmtsForBlocks(ctx, varDecl->firstBlock, nullptr);
+            Emit("}\n");
+        }
+
 
         if (auto paramBlockType = varType->As<UniformParameterGroupType>())
         {
@@ -6475,20 +6491,27 @@ emitDeclImpl(decl, nullptr);
         // Need to emit appropriate modifiers here.
 
         auto layout = getVarLayout(ctx, varDecl);
-        
-        emitIRVarModifiers(ctx, layout);
 
-#if 0
-        switch (addressSpace)
+        if (!layout)
         {
-        default:
-            break;
+            // A global variable without a layout is just an
+            // ordinary global variable, and may need special
+            // modifiers to indicate it as such.
+            switch (getTarget(ctx))
+            {
+            case CodeGenTarget::HLSL:
+                // HLSL requires the `static` modifier on any
+                // global variables; otherwise they are assumed
+                // to be uniforms.
+                Emit("static ");
+                break;
 
-        case kIRAddressSpace_GroupShared:
-            emit("groupshared ");
-            break;
+            default:
+                break;
+            }
         }
-#endif
+
+        emitIRVarModifiers(ctx, layout);
 
         emitIRType(ctx, varType, getIRName(varDecl));
 
@@ -6496,6 +6519,13 @@ emitDeclImpl(decl, nullptr);
 
         emitIRLayoutSemantics(ctx, varDecl);
 
+        if (varDecl->firstBlock)
+        {
+            Emit(" = ");
+            emit(initFuncName);
+            Emit("()");
+        }
+
         emit(";\n");
     }