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, 15 insertions, 19 deletions

diff --git a/source/slang/modifier-defs.h b/source/slang/modifier-defs.h
index d7d0391e4..9a16a0bdd 100644
--- a/source/slang/modifier-defs.h
+++ b/source/slang/modifier-defs.h
@@ -25,32 +25,28 @@ SIMPLE_MODIFIER(Exported);
 
 #undef SIMPLE_MODIFIER
 
-// Base class for modifiers that mark something as "intrinsic"
-// and thus lacking a direct implementation in the language.
-ABSTRACT_SYNTAX_CLASS(IntrinsicModifierBase, Modifier)
-END_SYNTAX_CLASS()
-
-// A modifier that marks something as one of a small set of
-// truly intrinsic operations that the compiler knows about
-// directly.
-SYNTAX_CLASS(IntrinsicOpModifier, IntrinsicModifierBase)
+// A modifier that marks something as an operation that
+// has a one-to-one translation to the IR, and thus
+// has no direct definition in the high-level language.
+//
+SYNTAX_CLASS(IntrinsicOpModifier, Modifier)
 
-// token that names the intrinsic op
-FIELD(Token, opToken)
+    // token that names the intrinsic op
+    FIELD(Token, opToken)
 
-// The opcode for the intrinsic operation
-FIELD_INIT(IntrinsicOp, op, IntrinsicOp::Unknown)
+    // The opcode for the intrinsic operation
+    FIELD_INIT(IROp, op, kIROp_Nop)
 END_SYNTAX_CLASS()
 
 // A modifier that marks something as an intrinsic function,
 // for some subset of targets.
-SYNTAX_CLASS(TargetIntrinsicModifier, IntrinsicModifierBase)
-// Token that names the target that the operation
-// is an intrisic for.
-FIELD(Token, targetToken)
+SYNTAX_CLASS(TargetIntrinsicModifier, Modifier)
+    // Token that names the target that the operation
+    // is an intrisic for.
+    FIELD(Token, targetToken)
 
-// A custom definition for the operation
-FIELD(Token, definitionToken)
+    // A custom definition for the operation
+    FIELD(Token, definitionToken)
 END_SYNTAX_CLASS()
 
 // A modifier to tag something as an intrinsic that requires