Replace old notion of "intrinsic" operations

The code previously had an enumerated type for "intrinsic" operations, and allowed functions to be marked `__intrinsic_op(...)` to indicate the operation they map to.
The nature of the IR meant that each of these intrinsic ops had to have a corresponding IR opcode, but the `enum` types weren't the same.
This change cleans things up a bit by deciding that the `__intrinsic_op(...)` modifier names an actual IR opcode, and so the `IntrinsicOp` enum is gone.

The biggest source of complexity here is that there are certain operations that need to be "intrinsic"-ish for the purposes of the current AST-based translation path, because we need them to round-trip from source to AST and back.
Right now this is being handled by defining a bunch of "pseudo-ops" which can be used in the `__intrinsic_op` modifier, but which are *not* meant to be represented in the IR.
Currently I don't actually handle this during IR generation.
In the long run, once we are using IR for everything that needs cross-compilation, we should be able to eliminate the pseudo-ops in favor of just having these be ordinary (inline) functions defined in the stdlib (e.g., the `+=` operator can just have a direct definition).

There was a second category of modifier that gets a little caught up in this, which is the `__intrinsic` modifier, which got used in two ways:

1. A function marked `__intrinsic(glsl, ...)` had what I call a "target intrinsic" modifier, which specified how to lower it for a specific target (e.g., GLSL).

2. A function just marked `__intrinsic` was supposed to be a marker for "this function shouldn't be emitted in the output, because the implementation is expected to be provided"

The latter category of function should really be an `__intrinsic_op`, so I translated all those uses. I added a tiny bit of sugar so that `__intrinsic_op` without an explicit opcode will look up an opcode based on the name of the function being called, so that an operation like `sin` can automatically be plumbed through to an equivalent IR op. (The first category is a stopgap for the AST-based cross-compilation, and will hopefully be replaced by something better  as we get the IR-based path working).

Getting the switch from `__intrinsic` to `__intrinsic_op` working required shuffling around some code in `emit.cpp` that handles looking up those modifiers and emitting builtin operations appropriately during cross-compilation.

Depending on where we go with things, a possible extension of this approach is to allow multiple operands to `__intrinsic_op` so that the first specifies the opcode, and then the rest are literal arguments to specify "sub-ops." This could help us handle stuff like texture-fetch operations without an explosion in the number of opcodes. I still need to think about whether this is a good idea or not.

1 files changed, 21 insertions, 2 deletions

diff --git a/source/slang/lower-to-ir.cpp b/source/slang/lower-to-ir.cpp
index d4cac0337..a8acadb59 100644
--- a/source/slang/lower-to-ir.cpp
+++ b/source/slang/lower-to-ir.cpp
@@ -407,7 +407,7 @@ struct ExprLoweringVisitor : ExprVisitor<ExprLoweringVisitor, LoweredValInfo>
 
     LoweredValInfo lowerIntrinsicCall(
         InvokeExpr* expr,
-        IntrinsicOp intrinsicOp)
+        IROp intrinsicOp)
     {
         auto type = lowerSimpleType(context, expr->type);
 
@@ -431,6 +431,24 @@ struct ExprLoweringVisitor : ExprVisitor<ExprLoweringVisitor, LoweredValInfo>
         return LoweredValInfo::simple(getBuilder()->emitCallInst(type, getSimpleVal(loweredFunc), argCount, irArgs.Buffer()));
     }
 
+    IROp getIntrinsicOp(
+        Decl*                   decl,
+        IntrinsicOpModifier*    intrinsicOpMod)
+    {
+        if (int(intrinsicOpMod->op) != 0)
+            return intrinsicOpMod->op;
+
+        // No specified modifier? Then we need to look it up
+        // based on the name of the declaration...
+
+        auto name = decl->getName();
+        auto nameText = getText(name);
+
+        IROp op = findIROp(nameText.Buffer());
+        assert(op != kIROp_Invalid);
+        return op;
+    }
+
     LoweredValInfo visitInvokeExpr(InvokeExpr* expr)
     {
         // TODO: need to detect calls to builtins here, so that we can expand
@@ -443,7 +461,8 @@ struct ExprLoweringVisitor : ExprVisitor<ExprLoweringVisitor, LoweredValInfo>
             auto funcDecl = funcDeclRef.getDecl();
             if(auto intrinsicOpModifier = funcDecl->FindModifier<IntrinsicOpModifier>())
             {
-                return lowerIntrinsicCall(expr, intrinsicOpModifier->op);
+                auto op = getIntrinsicOp(funcDecl, intrinsicOpModifier);
+                return lowerIntrinsicCall(expr, op);
                 // 
             }
             // TODO: handle target intrinsic modifier too...