Don't use -ffunction-sections -fdata-sections on debug builds.

Unfortunately, on ELF there is not used attribute on the .o files,
so there is no easy way to keep the dump function alive.

If we are not gcing, we may as well produce non gcable files and
avoid the cost.

Linking a debug clang now takes 18.856225992 seconds, before it
took 21.206897447.

I will try avoiding --gc-sections -O3 on a followup patch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234159 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/cmake/modules/HandleLLVMOptions.cmake b/cmake/modules/HandleLLVMOptions.cmake
index 67f86a645267fdff1c9b8ae405b15b0b54041b6e..f4f96501ebaa1eddadd13a733ca1520ec4e8d803 100644 (file)
--- a/cmake/modules/HandleLLVMOptions.cmake
+++ b/cmake/modules/HandleLLVMOptions.cmake
@@ -486,7 +486,8 @@ endif()
 # But MinSizeRel seems to add that automatically, so maybe disable these
 # flags instead if LLVM_NO_DEAD_STRIP is set.
 if(NOT CYGWIN AND NOT WIN32)
-  if(NOT ${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
+  if(NOT ${CMAKE_SYSTEM_NAME} MATCHES "Darwin" AND
+     NOT uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG")
     check_c_compiler_flag("-Werror -fno-function-sections" C_SUPPORTS_FNO_FUNCTION_SECTIONS)
     if (C_SUPPORTS_FNO_FUNCTION_SECTIONS)
       # Don't add -ffunction-section if it can be disabled with -fno-function-sections.