[clang] [HLSL][SPIR-V] Add `-fspv-enable-maximal-reconvergence` flag to clang dxc. (PR #163474)
Lucie Choi via cfe-commits
cfe-commits at lists.llvm.org
Wed Oct 15 09:03:31 PDT 2025
https://github.com/luciechoi updated https://github.com/llvm/llvm-project/pull/163474
>From fce0b6bdb650b85b600cd2a00041cdda8e5d87a0 Mon Sep 17 00:00:00 2001
From: luciechoi <ychoi0407 at gmail.com>
Date: Tue, 14 Oct 2025 23:19:39 +0000
Subject: [PATCH 1/2] [HLSL] Add `-fspv-enable-maximal-reconvergence` flag to
clang dxc.
---
clang/include/clang/Basic/LangOptions.def | 1 +
clang/include/clang/Driver/Options.td | 9 +++++++++
clang/lib/CodeGen/CGHLSLRuntime.cpp | 4 ++++
clang/lib/Driver/ToolChains/Clang.cpp | 3 ++-
.../vk-features/maximal_reconvergence.hlsl | 17 +++++++++++++++++
5 files changed, 33 insertions(+), 1 deletion(-)
create mode 100644 clang/test/CodeGenHLSL/vk-features/maximal_reconvergence.hlsl
diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
index 9e850089ad87f..d32fecdb96f32 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -243,6 +243,7 @@ ENUM_LANGOPT(HLSLVersion, HLSLLangStd, 16, HLSL_Unset, NotCompatible, "HLSL Vers
LANGOPT(HLSLStrictAvailability, 1, 0, NotCompatible,
"Strict availability diagnostic mode for HLSL built-in functions.")
LANGOPT(HLSLSpvUseUnknownImageFormat, 1, 0, NotCompatible, "For storage images and texel buffers, sets the default format to 'Unknown' when not specified via the `vk::image_format` attribute. If this option is not used, the format is inferred from the resource's data type.")
+LANGOPT(HLSLSpvEnableMaximalReconvergence, 1, 0, NotCompatible, "Enables maximal reconvergence for SPIR-V codegen. This ensures that all control flow merges at the nearest possible merge point as defined by the Vulkan spec.")
LANGOPT(CUDAIsDevice , 1, 0, NotCompatible, "compiling for CUDA device")
LANGOPT(CUDAHostDeviceConstexpr, 1, 1, NotCompatible, "treating unattributed constexpr functions as __host__ __device__")
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 611b68e5281f0..c71d440dee74d 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -9600,6 +9600,15 @@ def fhlsl_spv_use_unknown_image_format
"from the resource's data type.">,
MarshallingInfoFlag<LangOpts<"HLSLSpvUseUnknownImageFormat">>;
+def fhlsl_spv_enable_maximal_reconvergence
+ : Flag<["-"], "fspv-enable-maximal-reconvergence">,
+ Group<dxc_Group>,
+ Visibility<[CC1Option, DXCOption]>,
+ HelpText<"Enables maximal reconvergence for SPIR-V codegen. This ensures "
+ "that all control flow merges at the nearest possible merge point "
+ "as defined by the Vulkan spec.">,
+ MarshallingInfoFlag<LangOpts<"HLSLSpvEnableMaximalReconvergence">>;
+
def no_wasm_opt : Flag<["--"], "no-wasm-opt">,
Group<m_Group>,
HelpText<"Disable the wasm-opt optimizer">,
diff --git a/clang/lib/CodeGen/CGHLSLRuntime.cpp b/clang/lib/CodeGen/CGHLSLRuntime.cpp
index 603cef9116dc2..ecab9336a9f82 100644
--- a/clang/lib/CodeGen/CGHLSLRuntime.cpp
+++ b/clang/lib/CodeGen/CGHLSLRuntime.cpp
@@ -519,6 +519,10 @@ void clang::CodeGen::CGHLSLRuntime::setHLSLEntryAttributes(
if (CGM.getCodeGenOpts().OptimizationLevel == 0)
Fn->addFnAttr(llvm::Attribute::OptimizeNone);
Fn->addFnAttr(llvm::Attribute::NoInline);
+
+ if (CGM.getLangOpts().HLSLSpvEnableMaximalReconvergence) {
+ Fn->addFnAttr("enable-maximal-reconvergence", "true");
+ }
}
static Value *buildVectorInput(IRBuilder<> &B, Function *F, llvm::Type *Ty) {
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index bf755739760c0..682aa394c96b3 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -3755,7 +3755,8 @@ static void RenderHLSLOptions(const ArgList &Args, ArgStringList &CmdArgs,
options::OPT_hlsl_entrypoint,
options::OPT_fdx_rootsignature_define,
options::OPT_fdx_rootsignature_version,
- options::OPT_fhlsl_spv_use_unknown_image_format};
+ options::OPT_fhlsl_spv_use_unknown_image_format,
+ options::OPT_fhlsl_spv_enable_maximal_reconvergence};
if (!types::isHLSL(InputType))
return;
for (const auto &Arg : ForwardedArguments)
diff --git a/clang/test/CodeGenHLSL/vk-features/maximal_reconvergence.hlsl b/clang/test/CodeGenHLSL/vk-features/maximal_reconvergence.hlsl
new file mode 100644
index 0000000000000..870fbabaac1bf
--- /dev/null
+++ b/clang/test/CodeGenHLSL/vk-features/maximal_reconvergence.hlsl
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -triple spirv1.6-unknown-vulkan1.3-compute -fspv-enable-maximal-reconvergence -emit-llvm -o - -O0 %s | FileCheck %s --check-prefixes=CHECK
+// RUN: %clang_cc1 -triple spirv1.6-unknown-vulkan1.3-compute -hlsl-entry test -fspv-enable-maximal-reconvergence -emit-llvm -o - -O0 %s | FileCheck %s --check-prefixes=CHECK-ENTRY
+
+[numthreads(1,1,1)]
+void main() {
+// CHECK: define void @main() [[attributeNumber:#[0-9]+]] {
+}
+
+// CHECK: attributes [[attributeNumber]] = {{.*}} "enable-maximal-reconvergence"="true" {{.*}}
+
+
+[numthreads(1,1,1)]
+void test() {
+// CHECK-ENTRY: define void @test() [[attributeNumber:#[0-9]+]] {
+}
+
+// CHECK-ENTRY: attributes [[attributeNumber]] = {{.*}} "enable-maximal-reconvergence"="true" {{.*}}
\ No newline at end of file
>From 1997b1037ae186f107dda36cc92ec4bd050d1e2c Mon Sep 17 00:00:00 2001
From: luciechoi <ychoi0407 at gmail.com>
Date: Wed, 15 Oct 2025 16:01:52 +0000
Subject: [PATCH 2/2] fix the feature description
---
clang/include/clang/Basic/LangOptions.def | 2 +-
clang/include/clang/Driver/Options.td | 6 +++---
.../test/CodeGenHLSL/vk-features/maximal_reconvergence.hlsl | 2 +-
3 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
index d32fecdb96f32..5f70b5149e585 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -243,7 +243,7 @@ ENUM_LANGOPT(HLSLVersion, HLSLLangStd, 16, HLSL_Unset, NotCompatible, "HLSL Vers
LANGOPT(HLSLStrictAvailability, 1, 0, NotCompatible,
"Strict availability diagnostic mode for HLSL built-in functions.")
LANGOPT(HLSLSpvUseUnknownImageFormat, 1, 0, NotCompatible, "For storage images and texel buffers, sets the default format to 'Unknown' when not specified via the `vk::image_format` attribute. If this option is not used, the format is inferred from the resource's data type.")
-LANGOPT(HLSLSpvEnableMaximalReconvergence, 1, 0, NotCompatible, "Enables maximal reconvergence for SPIR-V codegen. This ensures that all control flow merges at the nearest possible merge point as defined by the Vulkan spec.")
+LANGOPT(HLSLSpvEnableMaximalReconvergence, 1, 0, NotCompatible, "Enables the MaximallyReconvergesKHR execution mode for this module. This ensures that control flow reconverges at well-defined merge points as defined by the Vulkan spec.")
LANGOPT(CUDAIsDevice , 1, 0, NotCompatible, "compiling for CUDA device")
LANGOPT(CUDAHostDeviceConstexpr, 1, 1, NotCompatible, "treating unattributed constexpr functions as __host__ __device__")
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index c71d440dee74d..fb0cb0803111d 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -9604,9 +9604,9 @@ def fhlsl_spv_enable_maximal_reconvergence
: Flag<["-"], "fspv-enable-maximal-reconvergence">,
Group<dxc_Group>,
Visibility<[CC1Option, DXCOption]>,
- HelpText<"Enables maximal reconvergence for SPIR-V codegen. This ensures "
- "that all control flow merges at the nearest possible merge point "
- "as defined by the Vulkan spec.">,
+ HelpText<"Enables the MaximallyReconvergesKHR execution mode for this "
+ "module. This ensures that control flow reconverges at "
+ "well-defined merge points as defined by the Vulkan spec.">,
MarshallingInfoFlag<LangOpts<"HLSLSpvEnableMaximalReconvergence">>;
def no_wasm_opt : Flag<["--"], "no-wasm-opt">,
diff --git a/clang/test/CodeGenHLSL/vk-features/maximal_reconvergence.hlsl b/clang/test/CodeGenHLSL/vk-features/maximal_reconvergence.hlsl
index 870fbabaac1bf..f23ac7c5434ab 100644
--- a/clang/test/CodeGenHLSL/vk-features/maximal_reconvergence.hlsl
+++ b/clang/test/CodeGenHLSL/vk-features/maximal_reconvergence.hlsl
@@ -14,4 +14,4 @@ void test() {
// CHECK-ENTRY: define void @test() [[attributeNumber:#[0-9]+]] {
}
-// CHECK-ENTRY: attributes [[attributeNumber]] = {{.*}} "enable-maximal-reconvergence"="true" {{.*}}
\ No newline at end of file
+// CHECK-ENTRY: attributes [[attributeNumber]] = {{.*}} "enable-maximal-reconvergence"="true" {{.*}}
More information about the cfe-commits
mailing list