From 9cb9a97e44130e17e96f994c3e594aba69ea1ad5 Mon Sep 17 00:00:00 2001
From: Petr Hosek <phosek@google.com>
Date: Fri, 5 Jul 2024 22:56:15 -0700
Subject: [PATCH] [CMake] Use Clang to infer the target triple (#89425)

When using Clang as a compiler, use Clang to normalize the triple that's
used to construct path for runtime library build and install paths. This
ensures that paths are consistent and avoids the issue where the build
uses a different triple spelling.

Differential Revision: https://reviews.llvm.org/D140925
---
 clang/cmake/caches/Fuchsia-stage2.cmake       |  2 +-
 .../cmake/Modules/CompilerRTUtils.cmake       | 17 +++++++++++++----
 runtimes/CMakeLists.txt                       | 19 +++++++++++++++++++
 3 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/clang/cmake/caches/Fuchsia-stage2.cmake b/clang/cmake/caches/Fuchsia-stage2.cmake
index 9892b5d58e719b..52687a2cf8ea9c 100644
--- a/clang/cmake/caches/Fuchsia-stage2.cmake
+++ b/clang/cmake/caches/Fuchsia-stage2.cmake
@@ -141,7 +141,7 @@ if(WIN32 OR LLVM_WINSYSROOT)
   set(RUNTIMES_${target}_CMAKE_MODULE_LINKER_FLAGS ${WINDOWS_LINK_FLAGS} CACHE STRING "")
 endif()
 
-foreach(target aarch64-unknown-linux-gnu;armv7-unknown-linux-gnueabihf;i386-unknown-linux-gnu;riscv64-unknown-linux-gnu;x86_64-unknown-linux-gnu)
+foreach(target aarch64-linux-gnu;armv7-linux-gnueabihf;i386-linux-gnu;riscv64-linux-gnu;x86_64-linux-gnu)
   if(LINUX_${target}_SYSROOT)
     # Set the per-target builtins options.
     list(APPEND BUILTIN_TARGETS "${target}")
diff --git a/compiler-rt/cmake/Modules/CompilerRTUtils.cmake b/compiler-rt/cmake/Modules/CompilerRTUtils.cmake
index 9c7fe64d0bd35d..cec7af929fb2b6 100644
--- a/compiler-rt/cmake/Modules/CompilerRTUtils.cmake
+++ b/compiler-rt/cmake/Modules/CompilerRTUtils.cmake
@@ -368,14 +368,23 @@ macro(construct_compiler_rt_default_triple)
           "Default triple for which compiler-rt runtimes will be built.")
   endif()
 
-  if ("${CMAKE_C_COMPILER_ID}" MATCHES "Clang")
+  if(CMAKE_C_COMPILER_ID MATCHES "Clang")
     set(option_prefix "")
     if (CMAKE_C_SIMULATE_ID MATCHES "MSVC")
       set(option_prefix "/clang:")
     endif()
-    execute_process(COMMAND ${CMAKE_C_COMPILER} ${option_prefix}--target=${COMPILER_RT_DEFAULT_TARGET_TRIPLE} ${option_prefix}-print-target-triple
-                    OUTPUT_VARIABLE COMPILER_RT_DEFAULT_TARGET_TRIPLE
-                    OUTPUT_STRIP_TRAILING_WHITESPACE)
+    set(print_target_triple ${CMAKE_C_COMPILER} ${option_prefix}--target=${COMPILER_RT_DEFAULT_TARGET_TRIPLE} ${option_prefix}-print-target-triple)
+    execute_process(COMMAND ${print_target_triple}
+      RESULT_VARIABLE result
+      OUTPUT_VARIABLE output
+      OUTPUT_STRIP_TRAILING_WHITESPACE)
+    if(result EQUAL 0)
+      set(COMPILER_RT_DEFAULT_TARGET_TRIPLE ${output})
+    else()
+      string(REPLACE ";" " " print_target_triple "${print_target_triple}")
+      # TODO(#97876): Report an error.
+      message(WARNING "Failed to execute `${print_target_triple}` to normalize target triple.")
+    endif()
   endif()
 
   string(REPLACE "-" ";" LLVM_TARGET_TRIPLE_LIST ${COMPILER_RT_DEFAULT_TARGET_TRIPLE})
diff --git a/runtimes/CMakeLists.txt b/runtimes/CMakeLists.txt
index 24f48511695915..830165c799c2ab 100644
--- a/runtimes/CMakeLists.txt
+++ b/runtimes/CMakeLists.txt
@@ -183,6 +183,25 @@ message(STATUS "LLVM default target triple: ${LLVM_DEFAULT_TARGET_TRIPLE}")
 
 set(LLVM_TARGET_TRIPLE "${LLVM_DEFAULT_TARGET_TRIPLE}")
 
+if(CMAKE_C_COMPILER_ID MATCHES "Clang")
+  set(option_prefix "")
+  if (CMAKE_C_SIMULATE_ID MATCHES "MSVC")
+    set(option_prefix "/clang:")
+  endif()
+  set(print_target_triple ${CMAKE_C_COMPILER} ${option_prefix}--target=${LLVM_DEFAULT_TARGET_TRIPLE} ${option_prefix}-print-target-triple)
+  execute_process(COMMAND ${print_target_triple}
+    RESULT_VARIABLE result
+    OUTPUT_VARIABLE output
+    OUTPUT_STRIP_TRAILING_WHITESPACE)
+  if(result EQUAL 0)
+    set(LLVM_DEFAULT_TARGET_TRIPLE ${output})
+  else()
+    string(REPLACE ";" " " print_target_triple "${print_target_triple}")
+    # TODO(#97876): Report an error.
+    message(WARNING "Failed to execute `${print_target_triple}` to normalize target triple.")
+  endif()
+endif()
+
 option(LLVM_INCLUDE_TESTS "Generate build targets for the runtimes unit tests." ON)
 option(LLVM_INCLUDE_DOCS "Generate build targets for the runtimes documentation." ON)
 option(LLVM_ENABLE_SPHINX "Use Sphinx to generate the runtimes documentation." OFF)