From 9280cfa0915962e8a192901657eb08f94403ab55 Mon Sep 17 00:00:00 2001
From: Chris Eibl <138194463+chris-eibl@users.noreply.github.com>
Date: Mon, 10 Mar 2025 10:50:45 +0100
Subject: [PATCH 1/2] use -flto=thin

---
 PCbuild/pyproject-clangcl.props | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/PCbuild/pyproject-clangcl.props b/PCbuild/pyproject-clangcl.props
index 30db6824f3caf5..d949c37d562594 100644
--- a/PCbuild/pyproject-clangcl.props
+++ b/PCbuild/pyproject-clangcl.props
@@ -41,7 +41,7 @@
       <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="$(Configuration) != 'Debug'">-flto %(AdditionalOptions)</AdditionalOptions>
+      <AdditionalOptions Condition="$(Configuration) != 'Debug'">-flto=thin %(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>

From 66186baada37ae08f4dbd4a84ecb73a053959d2f Mon Sep 17 00:00:00 2001
From: Chris Eibl <138194463+chris-eibl@users.noreply.github.com>
Date: Mon, 10 Mar 2025 10:56:33 +0100
Subject: [PATCH 2/2] blurb it

---
 .../next/Build/2025-03-10-10-52-25.gh-issue-131035.KF1w4j.rst   | 2 ++
 1 file changed, 2 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Build/2025-03-10-10-52-25.gh-issue-131035.KF1w4j.rst

diff --git a/Misc/NEWS.d/next/Build/2025-03-10-10-52-25.gh-issue-131035.KF1w4j.rst b/Misc/NEWS.d/next/Build/2025-03-10-10-52-25.gh-issue-131035.KF1w4j.rst
new file mode 100644
index 00000000000000..43c185610cce74
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2025-03-10-10-52-25.gh-issue-131035.KF1w4j.rst
@@ -0,0 +1,2 @@
+Use ``-flto=thin`` for faster build times using clang-cl on Windows. Patch by
+Chris Eibl.