[llvm-branch-commits] [openmp] release/18.x: [OpenMP] [cmake] Don't use -fno-semantic-interposition on Windows (#81113) (PR #81332)

[via llvm-branch-commits]

https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/81332

Backport 72f04fa0734f8559ad515f507a4a3ce3f461f196

Requested by: @mstorsjo

>From 9b34418e0883dba29b79a2c843055c7d7e632070 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Storsj=C3=B6?= <martin at martin.st>
Date: Thu, 8 Feb 2024 15:28:46 +0200
Subject: [PATCH] [OpenMP] [cmake] Don't use -fno-semantic-interposition on
 Windows (#81113)

This was added in 4b7beab4187ab0766c3d7b272511d5751431a8da. When the
flag was added implicitly elsewhere, it was added via
llvm/cmake/modules/HandleLLVMOptions.cmake, where it wasn't added on
Windows/Cygwin targets.

This avoids one warning per object file in OpenMP.

(cherry picked from commit 72f04fa0734f8559ad515f507a4a3ce3f461f196)
---
 openmp/cmake/HandleOpenMPOptions.cmake | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/openmp/cmake/HandleOpenMPOptions.cmake b/openmp/cmake/HandleOpenMPOptions.cmake
index 71346201129b68..9387d9b3b0ff75 100644
--- a/openmp/cmake/HandleOpenMPOptions.cmake
+++ b/openmp/cmake/HandleOpenMPOptions.cmake
@@ -46,7 +46,11 @@ append_if(OPENMP_HAVE_WEXTRA_FLAG "-Wno-extra" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
 append_if(OPENMP_HAVE_WPEDANTIC_FLAG "-Wno-pedantic" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
 append_if(OPENMP_HAVE_WMAYBE_UNINITIALIZED_FLAG "-Wno-maybe-uninitialized" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
 
-append_if(OPENMP_HAVE_NO_SEMANTIC_INTERPOSITION "-fno-semantic-interposition" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+if (NOT (WIN32 OR CYGWIN))
+  # This flag is not relevant on Windows; the flag is accepted, but produces warnings
+  # about argument unused during compilation.
+  append_if(OPENMP_HAVE_NO_SEMANTIC_INTERPOSITION "-fno-semantic-interposition" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+endif()
 append_if(OPENMP_HAVE_FUNCTION_SECTIONS "-ffunction-section" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
 append_if(OPENMP_HAVE_DATA_SECTIONS "-fdata-sections" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)