[clang] Warns that the WaveSize attribute is unsupported for the SPIR-V target. (PR #196004)

[Dan Brown via cfe-commits]

https://github.com/danbrown-amd created https://github.com/llvm/llvm-project/pull/196004

Addresses #187188.

>From 34438376a35e12e2d71891ef7e77b39ffbf506ec Mon Sep 17 00:00:00 2001
From: danbrown-amd <danbrown at amd.com>
Date: Wed, 6 May 2026 00:18:37 -0600
Subject: [PATCH] Warns that WaveSize attribute is unsupported for the SPIR-V
 target. Addresses #187188.

---
 clang/include/clang/Basic/DiagnosticSemaKinds.td | 4 ++++
 clang/lib/Sema/SemaHLSL.cpp                      | 4 +++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index e059260778631..e95d9ef58e9dd 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -13703,6 +13703,10 @@ def warn_attr_min_eq_max:  Warning<
 
 def err_hlsl_attribute_number_arguments_insufficient_shader_model: Error<
   "attribute %0 with %1 arguments requires shader model %2 or greater">;
+def warn_hlsl_wavesize_unsupported_spirv : Warning<
+  "attribute 'WaveSize' is not supported for the SPIR-V target; "
+  "consider using VK_EXT_subgroup_size_control">,
+  InGroup<HLSLAttributeStatement>;
 def err_hlsl_expect_arg_const_int_one_or_neg_one: Error<
   "argument %0 must be constant integer 1 or -1">;
 def err_invalid_hlsl_resource_type: Error<
diff --git a/clang/lib/Sema/SemaHLSL.cpp b/clang/lib/Sema/SemaHLSL.cpp
index aba1c5072a5fc..a33e54d15ba2a 100644
--- a/clang/lib/Sema/SemaHLSL.cpp
+++ b/clang/lib/Sema/SemaHLSL.cpp
@@ -1000,7 +1000,9 @@ void SemaHLSL::CheckEntryPoint(FunctionDecl *FD) {
       FD->setInvalidDecl();
     }
     if (const auto *WS = FD->getAttr<HLSLWaveSizeAttr>()) {
-      if (Ver < VersionTuple(6, 6)) {
+      if (TargetInfo.getTriple().isSPIRV()) {
+        Diag(WS->getLocation(), diag::warn_hlsl_wavesize_unsupported_spirv);
+      } else if (Ver < VersionTuple(6, 6)) {
         Diag(WS->getLocation(), diag::err_hlsl_attribute_in_wrong_shader_model)
             << WS << "6.6";
         FD->setInvalidDecl();