From ad3539574f52634c51523cfec1747e7565ad8876 Mon Sep 17 00:00:00 2001
From: Tim Foley <tfoley@nvidia.com>
Date: Wed, 6 Sep 2017 14:56:28 -0700
Subject: 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.
---
 source/slang/ir.cpp | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

(limited to 'source/slang/ir.cpp')

diff --git a/source/slang/ir.cpp b/source/slang/ir.cpp
index 3f07a685f..e3647a47b 100644
--- a/source/slang/ir.cpp
+++ b/source/slang/ir.cpp
@@ -13,15 +13,24 @@ namespace Slang
 #include "ir-inst-defs.h"
     };
 
+    //
 
-    static const IROp kIRIntrinsicOps[] =
+    IROp findIROp(char const* name)
     {
-        (IROp) 0,
+        // TODO: need to make this faster by using a dictionary...
 
-#define INTRINSIC(NAME) kIROp_Intrinsic_##NAME,
-#include "intrinsic-defs.h"
+        if (0) {}
 
-    };
+#define INST(ID, MNEMONIC, ARG_COUNT, FLAGS)  \
+    else if(strcmp(name, #MNEMONIC) == 0) return kIROp_##ID;
+
+#define PSEUDO_INST(ID)  \
+    else if(strcmp(name, #ID) == 0) return kIRPseudoOp_##ID;
+
+#include "ir-inst-defs.h"
+
+        return IROp(kIROp_Invalid);
+    }
 
     //
 
@@ -767,13 +776,13 @@ namespace Slang
 
     IRInst* IRBuilder::emitIntrinsicInst(
         IRType*         type,
-        IntrinsicOp     intrinsicOp,
+        IROp            op,
         UInt            argCount,
         IRValue* const* args)
     {
         auto inst = createInstWithTrailingArgs<IRInst>(
             this,
-            kIRIntrinsicOps[(int)intrinsicOp],
+            op,
             type,
             argCount,
             args);
-- 
cgit v1.2.3