[clang] [HLSL][SPIRV] Allow large z value in numthreads (PR #144934)

[Steven Perron via cfe-commits]

https://github.com/s-perron created https://github.com/llvm/llvm-project/pull/144934

The current validation checks for numthreads assume that the target is
DXIL so the version checks inadvertently issue error when targeting
SPIR-V.


>From 0b809d5a51a76ef76a68574b8dc447de10d4654a Mon Sep 17 00:00:00 2001
From: Steven Perron <stevenperron at google.com>
Date: Thu, 19 Jun 2025 13:56:27 -0400
Subject: [PATCH] [HLSL][SPIRV] Allow large z value in numthreads

The current validation checks for numthreads assume that the target is
DXIL so the version checks inadvertently issue error when targeting
SPIR-V.
---
 clang/lib/Sema/SemaHLSL.cpp          |  7 +++++--
 clang/test/SemaHLSL/num_threads.hlsl | 16 ++++++++++++----
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/clang/lib/Sema/SemaHLSL.cpp b/clang/lib/Sema/SemaHLSL.cpp
index b55f4fd786b58..9f39c077cea7a 100644
--- a/clang/lib/Sema/SemaHLSL.cpp
+++ b/clang/lib/Sema/SemaHLSL.cpp
@@ -1033,12 +1033,15 @@ void SemaHLSL::handleRootSignatureAttr(Decl *D, const ParsedAttr &AL) {
 void SemaHLSL::handleNumThreadsAttr(Decl *D, const ParsedAttr &AL) {
   llvm::VersionTuple SMVersion =
       getASTContext().getTargetInfo().getTriple().getOSVersion();
+  bool IsDXIL = getASTContext().getTargetInfo().getTriple().getArch() ==
+                llvm::Triple::dxil;
+
   uint32_t ZMax = 1024;
   uint32_t ThreadMax = 1024;
-  if (SMVersion.getMajor() <= 4) {
+  if (IsDXIL && SMVersion.getMajor() <= 4) {
     ZMax = 1;
     ThreadMax = 768;
-  } else if (SMVersion.getMajor() == 5) {
+  } else if (IsDXIL && SMVersion.getMajor() == 5) {
     ZMax = 64;
     ThreadMax = 1024;
   }
diff --git a/clang/test/SemaHLSL/num_threads.hlsl b/clang/test/SemaHLSL/num_threads.hlsl
index b5f9ad6c33cd6..96200312bbf69 100644
--- a/clang/test/SemaHLSL/num_threads.hlsl
+++ b/clang/test/SemaHLSL/num_threads.hlsl
@@ -10,6 +10,8 @@
 // RUN: %clang_cc1 -triple dxil-pc-shadermodel5.0-compute -x hlsl -ast-dump -o - %s -DFAIL -verify
 // RUN: %clang_cc1 -triple dxil-pc-shadermodel4.0-compute -x hlsl -ast-dump -o - %s -DFAIL -verify
 
+// RUN: %clang_cc1 -triple spirv-pc-vulkan1.3-compute -x hlsl -ast-dump -o - %s | FileCheck %s --check-prefixes=CHECK,CHECK-SPIRV
+
 #if __SHADER_TARGET_STAGE == __SHADER_STAGE_COMPUTE || __SHADER_TARGET_STAGE == __SHADER_STAGE_MESH || __SHADER_TARGET_STAGE == __SHADER_STAGE_AMPLIFICATION || __SHADER_TARGET_STAGE == __SHADER_STAGE_LIBRARY
 #ifdef FAIL
 
@@ -88,24 +90,30 @@ int entry() {
 
 // Because these two attributes match, they should both appear in the AST
 [numthreads(2,2,1)]
-// CHECK: HLSLNumThreadsAttr 0x{{[0-9a-fA-F]+}} <line:90:2, col:18> 2 2 1
+// CHECK: HLSLNumThreadsAttr 0x{{[0-9a-fA-F]+}} <line:{{[0-9]+}}:2, col:18> 2 2 1
 int secondFn();
 
 [numthreads(2,2,1)]
-// CHECK: HLSLNumThreadsAttr 0x{{[0-9a-fA-F]+}} <line:94:2, col:18> 2 2 1
+// CHECK: HLSLNumThreadsAttr 0x{{[0-9a-fA-F]+}} <line:{{[0-9]+}}:2, col:18> 2 2 1
 int secondFn() {
   return 1;
 }
 
 [numthreads(4,2,1)]
-// CHECK: HLSLNumThreadsAttr 0x{{[0-9a-fA-F]+}} <line:100:2, col:18> 4 2 1
+// CHECK: HLSLNumThreadsAttr 0x{{[0-9a-fA-F]+}} <line:{{[0-9]+}}:2, col:18> 4 2 1
 int onlyOnForwardDecl();
 
-// CHECK: HLSLNumThreadsAttr 0x{{[0-9a-fA-F]+}} <line:100:2, col:18> Inherited 4 2 1
+// CHECK: HLSLNumThreadsAttr 0x{{[0-9a-fA-F]+}} <line:{{[0-9]+}}:2, col:18> Inherited 4 2 1
 int onlyOnForwardDecl() {
   return 1;
 }
 
+#ifdef __spirv__ 
+[numthreads(4,2,128)]
+// CHECK-SPIRV: HLSLNumThreadsAttr 0x{{[0-9a-fA-F]+}} <line:{{[0-9]+}}:2, col:20> 4 2 128
+int largeZ();
+#endif 
+
 #else // Vertex and Pixel only beyond here
 // expected-error-re at +1 {{attribute 'numthreads' is unsupported in '{{[A-Za-z]+}}' shaders, requires one of the following: compute, amplification, mesh}}
 [numthreads(1,1,1)]