From 42dd4cd2ed143450910a669f30a5d4118f00e52a Mon Sep 17 00:00:00 2001
From: Steve Dower <steve.dower@python.org>
Date: Mon, 13 Jul 2026 18:44:02 +0100
Subject: [PATCH 1/2] gh-153668: Temporarily disable unicodectype.c
 optimization on WinARM64 due to compiler bug

---
 PCbuild/pyproject.props    | 2 ++
 PCbuild/pythoncore.vcxproj | 5 ++++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/PCbuild/pyproject.props b/PCbuild/pyproject.props
index 7435c53e3fdcf9f..155ce3889c1c87f 100644
--- a/PCbuild/pyproject.props
+++ b/PCbuild/pyproject.props
@@ -40,6 +40,8 @@
     <!-- See https://developercommunity.visualstudio.com/t/Regression-in-MSVC-1433-1434-ARM64-co/10224361 -->
     <MSVCHasBrokenARM64Clamping Condition="$(_VCToolsVersion) == '14.34' or $(_VCToolsVersion) == '14.35'">true</MSVCHasBrokenARM64Clamping>
     <MSVCHasBrokenARM64SignExtension Condition="$(_VCToolsVersion) == '14.37'">true</MSVCHasBrokenARM64SignExtension>
+    <!-- See gh-153668 and https://developercommunity.visualstudio.com/t/ARM64-compiler-uses-excessive-memory-on/11120089 -->
+    <MSVCHasBrokenARM64UniDbOpt Condition="$(_VCToolsVersion) == '14.51'">true</MSVCHasBrokenARM64UniDbOpt>
   </PropertyGroup>
 
   <PropertyGroup>
diff --git a/PCbuild/pythoncore.vcxproj b/PCbuild/pythoncore.vcxproj
index 47296a93424a8f6..d938e7f7c2961dc 100644
--- a/PCbuild/pythoncore.vcxproj
+++ b/PCbuild/pythoncore.vcxproj
@@ -576,7 +576,10 @@
     <ClCompile Include="..\Objects\typeobject.c" />
     <ClCompile Include="..\Objects\typevarobject.c" />
     <ClCompile Include="..\Objects\unicode_format.c" />
-    <ClCompile Include="..\Objects\unicodectype.c" />
+    <ClCompile Include="..\Objects\unicodectype.c">
+      <!-- gh-153668: Temporarily disabled due to a compiler bug -->
+      <Optimization Condition="$(Platform) == 'ARM64' and $(MSVCHasBrokenARM64UniDbOpt) == 'true'">Disabled</Optimization>
+    </ClCompile>
     <ClCompile Include="..\Objects\unicode_formatter.c" />
     <ClCompile Include="..\Objects\unicode_writer.c" />
     <ClCompile Include="..\Objects\unicodeobject.c" />

From eb7f9d7f230040985d7be21b0118ac831fefad8d Mon Sep 17 00:00:00 2001
From: Steve Dower <steve.dower@python.org>
Date: Mon, 13 Jul 2026 23:55:53 +0100
Subject: [PATCH 2/2] Only disable during Release (not PGO)

---
 PCbuild/pythoncore.vcxproj | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/PCbuild/pythoncore.vcxproj b/PCbuild/pythoncore.vcxproj
index d938e7f7c2961dc..91b7a680f320452 100644
--- a/PCbuild/pythoncore.vcxproj
+++ b/PCbuild/pythoncore.vcxproj
@@ -578,7 +578,7 @@
     <ClCompile Include="..\Objects\unicode_format.c" />
     <ClCompile Include="..\Objects\unicodectype.c">
       <!-- gh-153668: Temporarily disabled due to a compiler bug -->
-      <Optimization Condition="$(Platform) == 'ARM64' and $(MSVCHasBrokenARM64UniDbOpt) == 'true'">Disabled</Optimization>
+      <Optimization Condition="$(Platform) == 'ARM64' and $(Configuration) == 'Release' and $(MSVCHasBrokenARM64UniDbOpt) == 'true'">Disabled</Optimization>
     </ClCompile>
     <ClCompile Include="..\Objects\unicode_formatter.c" />
     <ClCompile Include="..\Objects\unicode_writer.c" />