[llvm-branch-commits] [clang] [CMake][Release] Disable PGO (#88465) (PR #89000)

[Tom Stellard via llvm-branch-commits]

https://github.com/tstellar created https://github.com/llvm/llvm-project/pull/89000

Running the test-release.sh script with PGO enabled causes build errors like:

ld.lld: error: Function Import: link error: linking module flags
'ProfileSummary': IDs have conflicting values

I believe this a build system bug due to the PGO profile data being generated unconditionally. If you run `ninja check-all` and then `ninja install` like we do in test-release.sh, then the profile data is regenerated during `ninja install` and some of the clang tools which are not test dependencies get build during the ninja install step with different profile data. When these tools link against the LLVM libraries, like libSupport, we end up with these errors.

(cherry picked from commit 0d2bb7f017f13ceae793fab7d83d3e67e8d8d8f8)

>From 715f7249949778c20de5e15d8ba58103610d6a16 Mon Sep 17 00:00:00 2001
From: Tom Stellard <tstellar at redhat.com>
Date: Fri, 12 Apr 2024 15:10:04 -0700
Subject: [PATCH] [CMake][Release] Disable PGO (#88465)

Running the test-release.sh script with PGO enabled causes build errors
like:

ld.lld: error: Function Import: link error: linking module flags
'ProfileSummary': IDs have conflicting values

I believe this a build system bug due to the PGO profile data being
generated unconditionally. If you run `ninja check-all` and then `ninja
install` like we do in test-release.sh, then the profile data is
regenerated during `ninja install` and some of the clang tools which are
not test dependencies get build during the ninja install step with
different profile data. When these tools link against the LLVM
libraries, like libSupport, we end up with these errors.

(cherry picked from commit 0d2bb7f017f13ceae793fab7d83d3e67e8d8d8f8)
---
 clang/cmake/caches/Release.cmake | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/cmake/caches/Release.cmake b/clang/cmake/caches/Release.cmake
index 1ca9138b980731..bd1f688d61a7ea 100644
--- a/clang/cmake/caches/Release.cmake
+++ b/clang/cmake/caches/Release.cmake
@@ -4,7 +4,7 @@
 
 # General Options
 set(LLVM_RELEASE_ENABLE_LTO THIN CACHE STRING "")
-set(LLVM_RELEASE_ENABLE_PGO ON CACHE BOOL "")
+set(LLVM_RELEASE_ENABLE_PGO OFF CACHE BOOL "")
 
 set(CMAKE_BUILD_TYPE RELEASE CACHE STRING "")