[llvm-branch-commits] [clang] release/21.x: [CMake][Release] Build with -ffat-lto-objects (#140381) (PR #151245)

[Tom Stellard via llvm-branch-commits]

https://github.com/tstellar updated https://github.com/llvm/llvm-project/pull/151245

>From ab1d1813b343c6f274beec751bcfef3b8e75ba7b Mon Sep 17 00:00:00 2001
From: Tom Stellard <tstellar at redhat.com>
Date: Tue, 29 Jul 2025 15:33:49 -0700
Subject: [PATCH] [CMake][Release] Build with -ffat-lto-objects (#140381)

Fixes #133580

(cherry picked from commit cff9ae7a15a5d1e9bf385aceea02daf5ed8482fe)
---
 clang/cmake/caches/Release.cmake                           | 6 +++++-
 clang/cmake/caches/release_cpack_pre_build_strip_lto.cmake | 5 +++++
 2 files changed, 10 insertions(+), 1 deletion(-)
 create mode 100644 clang/cmake/caches/release_cpack_pre_build_strip_lto.cmake

diff --git a/clang/cmake/caches/Release.cmake b/clang/cmake/caches/Release.cmake
index fb12dfcdcb5a5..a523cc561b3f9 100644
--- a/clang/cmake/caches/Release.cmake
+++ b/clang/cmake/caches/Release.cmake
@@ -102,7 +102,7 @@ if (LLVM_RELEASE_ENABLE_LTO)
   # FIXME: We can't use LLVM_ENABLE_LTO=Thin here, because it causes the CMake
   # step for the libcxx build to fail.  CMAKE_INTERPROCEDURAL_OPTIMIZATION does
   # enable ThinLTO, though.
-  set(RUNTIMES_CMAKE_ARGS "-DCMAKE_INTERPROCEDURAL_OPTIMIZATION=ON -DLLVM_ENABLE_LLD=ON" CACHE STRING "")
+  set(RUNTIMES_CMAKE_ARGS "-DCMAKE_INTERPROCEDURAL_OPTIMIZATION=ON -DLLVM_ENABLE_LLD=ON -DLLVM_ENABLE_FATLTO=ON" CACHE STRING "")
 endif()
 
 # Stage 1 Common Config
@@ -144,3 +144,7 @@ set_final_stage_var(CPACK_GENERATOR "TXZ" STRING)
 set_final_stage_var(CPACK_ARCHIVE_THREADS "0" STRING)
 
 set_final_stage_var(LLVM_USE_STATIC_ZSTD "ON" BOOL)
+if (LLVM_RELEASE_ENABLE_LTO)
+  set_final_stage_var(LLVM_ENABLE_FATLTO "ON" BOOL)
+  set_final_stage_var(CPACK_PRE_BUILD_SCRIPTS "${CMAKE_CURRENT_LIST_DIR}/release_cpack_pre_build_strip_lto.cmake" STRING)
+endif()
diff --git a/clang/cmake/caches/release_cpack_pre_build_strip_lto.cmake b/clang/cmake/caches/release_cpack_pre_build_strip_lto.cmake
new file mode 100644
index 0000000000000..743b64fe00f58
--- /dev/null
+++ b/clang/cmake/caches/release_cpack_pre_build_strip_lto.cmake
@@ -0,0 +1,5 @@
+file(GLOB files ${CPACK_TEMPORARY_INSTALL_DIRECTORY}/lib/*.a)
+
+foreach(file ${files})
+  execute_process(COMMAND ${CPACK_TEMPORARY_INSTALL_DIRECTORY}/bin/llvm-strip --no-strip-all -R .llvm.lto ${file})
+endforeach()