https://github.com/python/cpython/commit/d8a1cf469e40b538a84e583ac1d5d34418ed9a6a
commit: d8a1cf469e40b538a84e583ac1d5d34418ed9a6a
branch: main
author: Chris Eibl <138194463+chris-e...@users.noreply.github.com>
committer: zooba <steve.do...@microsoft.com>
date: 2025-03-04T19:29:03Z
summary:
gh-130090: Support PGO for clang-cl on Windows (GH-129907)
files:
A Misc/NEWS.d/next/Build/2025-02-13-19-21-41.gh-issue-130090.3ngJaV.rst
A PCbuild/pyproject-clangcl.props
M Misc/ACKS
M PCbuild/_freeze_module.vcxproj
M PCbuild/pyproject.props
M PCbuild/pythoncore.vcxproj
M PCbuild/readme.txt
diff --git a/Misc/ACKS b/Misc/ACKS
index 2a68b69f161041..7bf1d9c99ea24c 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -504,6 +504,7 @@ Grant Edwards
Vlad Efanov
Zvi Effron
John Ehresman
+Chris Eibl
Tal Einat
Eric Eisner
Andrew Eland
diff --git
a/Misc/NEWS.d/next/Build/2025-02-13-19-21-41.gh-issue-130090.3ngJaV.rst
b/Misc/NEWS.d/next/Build/2025-02-13-19-21-41.gh-issue-130090.3ngJaV.rst
new file mode 100644
index 00000000000000..9ee7d5cdd8ae8a
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2025-02-13-19-21-41.gh-issue-130090.3ngJaV.rst
@@ -0,0 +1,2 @@
+Building with ``PlatformToolset=ClangCL`` on Windows now supports PGO
+(profile guided optimization). Patch by Chris Eibl with invaluable support
from Steve Dover.
diff --git a/PCbuild/_freeze_module.vcxproj b/PCbuild/_freeze_module.vcxproj
index e12876114459bc..44292ee32b19fa 100644
--- a/PCbuild/_freeze_module.vcxproj
+++ b/PCbuild/_freeze_module.vcxproj
@@ -92,6 +92,7 @@
<AdditionalIncludeDirectories>$(IntDir);%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
<Optimization>Disabled</Optimization>
<WholeProgramOptimization>false</WholeProgramOptimization>
+ <AdditionalOptions Condition="$(PlatformToolset) ==
'ClangCL'">%(AdditionalOptions) -fno-lto</AdditionalOptions>
</ClCompile>
<Link>
<SubSystem>Console</SubSystem>
diff --git a/PCbuild/pyproject-clangcl.props b/PCbuild/pyproject-clangcl.props
new file mode 100644
index 00000000000000..30db6824f3caf5
--- /dev/null
+++ b/PCbuild/pyproject-clangcl.props
@@ -0,0 +1,50 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="15.0"
xmlns="http://schemas.microsoft.com/developer/msbuild/2003";>
+ <PropertyGroup Label="Globals">
+ <__PyprojectClangCl_Props_Imported>true</__PyprojectClangCl_Props_Imported>
+ </PropertyGroup>
+
+ <PropertyGroup>
+ <!-- CLANG_PROFILE_PATH is configurable for "remote PGO builds"
+ For convenience, we also accept paths without trailing slashes.
+ -->
+ <CLANG_PROFILE_PATH Condition="'$(CLANG_PROFILE_PATH)' ==
''">$(OutDir)</CLANG_PROFILE_PATH>
+ <_CLANG_PROFILE_PATH>$(CLANG_PROFILE_PATH)</_CLANG_PROFILE_PATH>
+ <_CLANG_PROFILE_PATH
Condition="!HasTrailingSlash($(_CLANG_PROFILE_PATH))">$(_CLANG_PROFILE_PATH)\</_CLANG_PROFILE_PATH>
+ </PropertyGroup>
+
+ <ItemGroup>
+ <_profrawFiles Include="$(OutDir)instrumented\$(TargetName)_*.profraw" />
+ </ItemGroup>
+
+ <Target Name="EnsureClangProfileData" BeforeTargets="PrepareForBuild"
+ Condition="'$(SupportPGO)' and $(Configuration) == 'PGUpdate'">
+ <Error Text="PGO run did not succeed (no $(TargetName)_*.profraw files)
and there is no data to merge"
+ Condition="$(RequireProfileData) == 'true' and @(_profrawFiles) ==
''" />
+ </Target>
+
+ <Target Name="MergeClangProfileData" BeforeTargets="PrepareForBuild"
+ Condition="'$(SupportPGO)' and $(Configuration) == 'PGUpdate'"
+ Inputs="@(_profrawFiles)"
+ Outputs="$(OutDir)instrumented\profdata.profdata">
+ <Exec
+ Command='"$(LLVMInstallDir)\bin\llvm-profdata.exe" merge
-output="$(OutDir)instrumented\profdata.profdata"
"$(OutDir)instrumented\*_*.profraw"' />
+ </Target>
+
+ <Target Name="CleanClangProfileData" BeforeTargets="Clean">
+ <Delete Files="@(_profrawFiles)" TreatErrorsAsWarnings="true" />
+ <Delete Files="$(OutDir)instrumented\profdata.profdata"
TreatErrorsAsWarnings="true" />
+ </Target>
+
+ <ItemDefinitionGroup>
+ <ClCompile>
+ <AdditionalOptions>-Wno-deprecated-non-prototype -Wno-unused-label
-Wno-pointer-sign -Wno-incompatible-pointer-types-discards-qualifiers
-Wno-unused-function %(AdditionalOptions)</AdditionalOptions>
+ <AdditionalOptions Condition="'$(Platform)' == 'Win32'">-m32
%(AdditionalOptions)</AdditionalOptions>
+ <AdditionalOptions Condition="'$(Platform)' == 'x64'">-m64
%(AdditionalOptions)</AdditionalOptions>
+ <AdditionalOptions Condition="$(Configuration) != 'Debug'">-flto
%(AdditionalOptions)</AdditionalOptions>
+ <AdditionalOptions Condition="$(SupportPGO) and $(Configuration) ==
'PGInstrument'">-fprofile-instr-generate=$(_CLANG_PROFILE_PATH)$(TargetName)_%m.profraw
%(AdditionalOptions)</AdditionalOptions>
+ <AdditionalOptions Condition="$(SupportPGO) and $(Configuration) ==
'PGUpdate'">-fprofile-instr-use=$(OutDir)instrumented\profdata.profdata
-Wno-profile-instr-unprofiled %(AdditionalOptions)</AdditionalOptions>
+ </ClCompile>
+ </ItemDefinitionGroup>
+
+</Project>
diff --git a/PCbuild/pyproject.props b/PCbuild/pyproject.props
index 17abfa85201a90..2681e2d42e8996 100644
--- a/PCbuild/pyproject.props
+++ b/PCbuild/pyproject.props
@@ -24,6 +24,9 @@
<LinkIncremental Condition="$(Configuration) !=
'Debug'">false</LinkIncremental>
</PropertyGroup>
+ <!-- We need the above overridden OutDir, so this must be imported after
PropertyGroup -->
+ <Import Project="pyproject-clangcl.props" Condition="$(PlatformToolset) ==
'ClangCL' and $(__PyprojectClangCl_Props_Imported) != 'true'" />
+
<PropertyGroup Condition="$(TargetExt) != ''">
<TargetNameExt>$(TargetName)$(TargetExt)</TargetNameExt>
<_TargetNameSep>$(TargetNameExt.LastIndexOf(`.`))</_TargetNameSep>
@@ -69,8 +72,6 @@
<ControlFlowGuard Condition="$(EnableControlFlowGuard) !=
''">$(EnableControlFlowGuard)</ControlFlowGuard>
<MultiProcessorCompilation>true</MultiProcessorCompilation>
<AdditionalOptions>/utf-8 %(AdditionalOptions)</AdditionalOptions>
- <AdditionalOptions Condition="$(PlatformToolset) ==
'ClangCL'">-Wno-deprecated-non-prototype -Wno-unused-label -Wno-pointer-sign
-Wno-incompatible-pointer-types-discards-qualifiers -Wno-unused-function
%(AdditionalOptions)</AdditionalOptions>
- <AdditionalOptions Condition="$(Configuration) != 'Debug' and
$(PlatformToolset) == 'ClangCL'">-flto %(AdditionalOptions)</AdditionalOptions>
<AdditionalOptions Condition="$(MSVCHasBrokenARM64Clamping) == 'true'
and $(Platform) == 'ARM64'">-d2pattern-opt-disable:-932189325
%(AdditionalOptions)</AdditionalOptions>
<AdditionalOptions Condition="$(MSVCHasBrokenARM64SignExtension) ==
'true' and $(Platform) == 'ARM64'">-d2ssa-patterns-all-
%(AdditionalOptions)</AdditionalOptions>
<AdditionalOptions Condition="$(GenerateSourceDependencies) ==
'true'">/sourceDependencies "$(IntDir.Trim(`\`))"
%(AdditionalOptions)</AdditionalOptions>
@@ -186,7 +187,7 @@ public override bool Execute() {
Targets="CleanAll" />
</Target>
- <Target Name="CopyPGCFiles" BeforeTargets="PrepareForBuild"
Condition="$(Configuration) == 'PGUpdate'">
+ <Target Name="CopyPGCFiles" BeforeTargets="PrepareForBuild"
Condition="$(Configuration) == 'PGUpdate' and $(PlatformToolset) != 'ClangCL'">
<ItemGroup>
<_PGCFiles Include="$(OutDir)instrumented\$(TargetName)!*.pgc" />
<_PGDFile Include="$(OutDir)instrumented\$(TargetName).pgd" />
@@ -194,7 +195,7 @@ public override bool Execute() {
</ItemGroup>
<Delete Files="@(_CopyFiles->'$(OutDir)%(Filename)%(Extension)')" />
<Error Text="PGO run did not succeed (no $(TargetName)!*.pgc files) and
there is no data to merge"
- Condition="$(RequirePGCFiles) == 'true' and @(_PGCFiles) == ''" />
+ Condition="$(RequireProfileData) == 'true' and @(_PGCFiles) == ''"
/>
<Copy SourceFiles="@(_CopyFiles)"
DestinationFolder="$(OutDir)"
UseHardLinksIfPossible="true"
diff --git a/PCbuild/pythoncore.vcxproj b/PCbuild/pythoncore.vcxproj
index 9ebf58ae8a9bc4..3b3c3972987db8 100644
--- a/PCbuild/pythoncore.vcxproj
+++ b/PCbuild/pythoncore.vcxproj
@@ -81,7 +81,7 @@
</ImportGroup>
<PropertyGroup>
<KillPython>true</KillPython>
- <RequirePGCFiles>true</RequirePGCFiles>
+ <RequireProfileData>true</RequireProfileData>
<IncludeExternals Condition="$(IncludeExternals) == '' and
Exists('$(zlibDir)\zlib.h')">true</IncludeExternals>
<IncludeExternals Condition="$(IncludeExternals) ==
''">false</IncludeExternals>
</PropertyGroup>
diff --git a/PCbuild/readme.txt b/PCbuild/readme.txt
index 693fcee5f90ce2..33952d31681cbc 100644
--- a/PCbuild/readme.txt
+++ b/PCbuild/readme.txt
@@ -52,6 +52,45 @@ Release
settings, though without PGO.
+Building Python using Clang/LLVM
+--------------------------------
+
+See https://learn.microsoft.com/cpp/build/clang-support-msbuild
+for how to install and use clang-cl bundled with Microsoft Visual Studio.
+You can use the IDE to switch to clang-cl for local development,
+but because this alters the *.vcxproj files, the recommended way is
+to use build.bat:
+
+build.bat "/p:PlatformToolset=ClangCL"
+
+All other build.bat options continue to work as with MSVC, so this
+will create a 64bit release binary.
+
+You can also use a specific version of clang-cl downloaded from
+https://github.com/llvm/llvm-project/releases, e.g.
+clang+llvm-18.1.8-x86_64-pc-windows-msvc.tar.xz.
+Given you have extracted that to <my-clang-dir>, you can use it like so
+build.bat --pgo "/p:PlatformToolset=ClangCL" "/p:LLVMInstallDir=<my-clang-dir>
"/p:LLVMToolsVersion=18"
+
+Setting LLVMToolsVersion to the major version is enough, although you
+can be specific and use 18.1.8 in the above example, too.
+
+Use the --pgo option to build with PGO (Profile Guided Optimization).
+
+However, if you want to run the PGO task
+on a different host than the build host, you must pass
+"/p:CLANG_PROFILE_PATH=<relative-path-to-instrumented-dir-on-remote-host>"
+in the PGInstrument step to make sure the profile data is generated
+into the instrumented directory when running the PGO task.
+E.g., if you place the instrumented binaries into the folder
+"workdir/instrumented" and then run the PGO task using "workdir"
+as the current working directory, the usage is
+"/p:CLANG_PROFILE_PATH=instrumented"
+
+Like in the MSVC case, after fetching (or manually copying) the instrumented
+folder back into your build tree, you can continue with the PGUpdate
+step with no further parameters.
+
Building Python using the build.bat script
----------------------------------------------
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