[HLSL] Treat main as any other function

[llvm-beanz]

HLSL doesn't distinguish main from any other function. It does treat entry points special, but they're not required to be called main so we have a different attribute annotation to mark them.

At the moment this change really just changes the mangling of functions named main in the Itanium mangling.

Fixes #110517

[llvmbot]

@llvm/pr-subscribers-hlsl

@llvm/pr-subscribers-clang

Author: Chris B (llvm-beanz)

Changes

HLSL doesn't distinguish main from any other function. It does treat entry points special, but they're not required to be called main so we have a different attribute annotation to mark them.

At the moment this change really just changes the mangling of functions named main in the Itanium mangling.

Fixes #110517

---

Full diff: https://github.com/llvm/llvm-project/pull/110546.diff

3 Files Affected:

• (modified) clang/lib/AST/Decl.cpp (+1)
• (modified) clang/test/CodeGenHLSL/builtins/wave_get_lane_index_do_while.hlsl (+1-1)
• (modified) clang/test/Options/enable_16bit_types_validation_spirv.hlsl (+1-1)

diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index a14b1b33d35efc..84ef9f74582ef6 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -3302,6 +3302,7 @@ bool FunctionDecl::isImmediateFunction() const {
 
 bool FunctionDecl::isMain() const {
   return isNamed(this, "main") && !getLangOpts().Freestanding &&
+         !getLangOpts().HLSL &&
          (getDeclContext()->getRedeclContext()->isTranslationUnit() ||
           isExternC());
 }
diff --git a/clang/test/CodeGenHLSL/builtins/wave_get_lane_index_do_while.hlsl b/clang/test/CodeGenHLSL/builtins/wave_get_lane_index_do_while.hlsl
index 9481b0d60a2723..c223b9117e9277 100644
--- a/clang/test/CodeGenHLSL/builtins/wave_get_lane_index_do_while.hlsl
+++ b/clang/test/CodeGenHLSL/builtins/wave_get_lane_index_do_while.hlsl
@@ -1,7 +1,7 @@
 // RUN: %clang_cc1 -std=hlsl2021 -finclude-default-header -x hlsl -triple \
 // RUN:   spirv-pc-vulkan-library %s -emit-llvm -disable-llvm-passes -o - | FileCheck %s
 
-// CHECK: define spir_func void @main() [[A0:#[0-9]+]] {
+// CHECK: define spir_func void @{{.*}}main{{.*}}() [[A0:#[0-9]+]] {
 void main() {
 // CHECK: entry:
 // CHECK:   %[[CT_ENTRY:[0-9]+]] = call token @llvm.experimental.convergence.entry()
diff --git a/clang/test/Options/enable_16bit_types_validation_spirv.hlsl b/clang/test/Options/enable_16bit_types_validation_spirv.hlsl
index aeb7a8369f4034..3e6734011c39ad 100644
--- a/clang/test/Options/enable_16bit_types_validation_spirv.hlsl
+++ b/clang/test/Options/enable_16bit_types_validation_spirv.hlsl
@@ -4,7 +4,7 @@
 // SPIRV: error: '-fnative-half-type' option requires target HLSL Version >= 2018, but HLSL Version is 'hlsl2016'
 
 // valid: "spirv-unknown-vulkan-library"
-// valid: define spir_func void @main() #0 {
+// valid: define spir_func void @{{.*}}main{{.*}}() #0 {
 
 [numthreads(1,1,1)]
 void main()

[bogner]

There is still logic elsewhere that sets the default entry point to "main", right? This looks right to me.

[s-perron]

This fixes the problem in #108567

[llvm-beanz]

There is still logic elsewhere that sets the default entry point to "main", right? This looks right to me.

Yes, and we apply the HLSLShader attribute to main and key generating the entry off that in clangCodeGen.