Fix wgsl legalization around __ref parameter. (#5597)

* Fix wgsl legalization around __ref parameter.

* Add intrinsic and test case.

2 files changed, 21 insertions, 0 deletions

diff --git a/source/slang/hlsl.meta.slang b/source/slang/hlsl.meta.slang
index 14f9f78f2..395ea5012 100644
--- a/source/slang/hlsl.meta.slang
+++ b/source/slang/hlsl.meta.slang
@@ -20645,3 +20645,22 @@ extension<T, L : IBufferDataLayout> RasterizerOrderedStructuredBuffer<T, L> : IR
 {
     int getCount() { uint count; uint stride; this.GetDimensions(count, stride); return count; }
 }
+
+//@public:
+
+/// Mark a variable as being workgroup uniform.
+/// @param v The variable to mark as workgroup uniform.
+/// @return The value of `v`.
+/// @remarks This intrinsic maps to `workgroupUniformLoad` when targeting WGSL and is a no-op on other targets.
+/// WGSL is strict on uniformity, and this intrinsic is needed to mark a variable as workgroup uniform in order
+// to silence uniformity errors in certain cases.
+T workgroupUniformLoad<T>(__ref T v)
+{
+    __target_switch
+    {
+    case wgsl:
+        __intrinsic_asm "workgroupUniformLoad(&($0))";
+    default:
+        return v;
+    }
+}
\ No newline at end of file
diff --git a/source/slang/slang-ir-wgsl-legalize.cpp b/source/slang/slang-ir-wgsl-legalize.cpp
index adb027668..4d617a169 100644
--- a/source/slang/slang-ir-wgsl-legalize.cpp
+++ b/source/slang/slang-ir-wgsl-legalize.cpp
@@ -1398,6 +1398,8 @@ struct LegalizeWGSLEntryPointContext
             {
             case kIROp_Var:
             case kIROp_Param:
+            case kIROp_GlobalParam:
+            case kIROp_GlobalVar:
                 continue;
             default:
                 break;