Support __target_intrinsic modifiers in IR codegen (#401)

The standard library already has a bunch of these decorations, since they were added to support Slang->Vulkan codegen on the AST-to-AST path. This change makes the IR code generator able to exploit the modifiers so that we pick up a bunch of Vulkan support "for free" in the short term.

The basic change is in `lower-to-ir.cpp` where we copy over any `TargetIntrinsicModifier`s to become `IRTargetIntrinsicDecoration`s with the same information. We then need a bit of logic in `ir.cpp` to make sure we clone them as needed.

The core work of using the modifiers is in `emit.cpp`, where I basically just copy-pasted the existing logic that applied in the AST path (all the AST-related code there is dead, and we should clean it up soon).

The big change that comes with this logic is that when dealing with a member function, the numbering of the argument used in the intrinsic definition string changes, so that `$0` refers to the base object (whereas before the base object was looked up via the base expression of a `MemberExpr` used for the function). This requires a bunch of the definitions in the library to be updated; hopefully I caught them all.

For kicks, I've re-enabled a cross-compilation test just to confirm that we are generating valid SPIR-V for code that performs texture-fetch operations. I don't expect us to keep that test enabled as-is in the long term, though, because it would be much better to instead use render-test to do the same thing. Alas, beefing up the Vulkan support in render-test is an outstanding work item, and I didn't want to pollute this change with more work along those lines.

1 files changed, 9 insertions, 0 deletions

diff --git a/source/slang/ir.cpp b/source/slang/ir.cpp
index b965f908c..77aac3f5a 100644
--- a/source/slang/ir.cpp
+++ b/source/slang/ir.cpp
@@ -3226,6 +3226,15 @@ namespace Slang
                 }
                 break;
 
+            case kIRDecorationOp_TargetIntrinsic:
+                {
+                    auto originalDecoration = (IRTargetIntrinsicDecoration*)dd;
+                    auto newDecoration = context->builder->addDecoration<IRTargetIntrinsicDecoration>(clonedValue);
+                    newDecoration->targetName = originalDecoration->targetName;
+                    newDecoration->definition = originalDecoration->definition;
+                }
+                break;
+
             default:
                 // Don't clone any decorations we don't understand.
                 break;