Tweaks for setting CMAKE_LINKER to lld-link

[thakis]

Summary

• Just look for "lld-link", not "lld-link.exe". llvm/cmake/platforms/WinMsvc.cmake for example sets CMAKE_LINKER to lld-link without .exe

• Stop passing -gwarf to the compiler in sanitizer options when lld is enabled -- there's no reason to use different debug information keyed off the linker. (If this was for MinGW, we should check for that instead.)

[rnk]

lgtm

That's old code... I guess nobody has tried building LLVM with asan on Windows in a while.

[smeenai]

llvm/cmake/modules/HandleLLVMOptions.cmake

15

Not your diff, but is this just setting LINKER_IS_LLD_LINK to true when LLVM_ENABLE_LLD is true? That seems wrong?

[thakis]

llvm/cmake/modules/HandleLLVMOptions.cmake

15

You're saying that this should be OR (WIN32 AND (LLVM_USE_LINKER STREQUAL "lld" OR LLVM_ENABLE_LLD)), right?

I think this whole conditional is a bit shaky:

• Since LLVM_ENABLE_LLD causes LLVM_USE_LINKER to be set, we should probably only look at the latter

• On Windows, as far as I know cmake always calls (lld-)link.exe (it certainly does with the Ninja generator, which is what I use), so I think this should really only check CMAKE_LINKER (…which by default is ignored on non-Windows).

But after this change, LINKER_IS_LLD_LINK is only used in lto-related contexts, and I'm guessing nobody uses lto to build llvm on windows yet, so it probably doesn't matter all that much.

We're planning to look at thinlto for chromium's llvm builds "soon", so we might revisit this then.

llvm/cmake/modules/HandleLLVMOptions.cmake

 # This CMake module is responsible for interpreting the user defined LLVM_
 # options and executing the appropriate CMake commands to realize the users'
 # selections.
 
 # This is commonly needed so make sure it's defined before we include anything
 # else.
 string(TOUPPER "${CMAKE_BUILD_TYPE}" uppercase_CMAKE_BUILD_TYPE)
 
 include(CheckCompilerVersion)
 include(HandleLLVMStdlib)
 include(CheckCCompilerFlag)
 include(CheckCXXCompilerFlag)
 include(CheckSymbolExists)
 
-if(CMAKE_LINKER MATCHES "lld-link\\.exe" OR (WIN32 AND LLVM_USE_LINKER STREQUAL "lld") OR LLVM_ENABLE_LLD)
+if(CMAKE_LINKER MATCHES "lld-link" OR (WIN32 AND LLVM_USE_LINKER STREQUAL "lld") OR LLVM_ENABLE_LLD)
   set(LINKER_IS_LLD_LINK TRUE)
 else()
   set(LINKER_IS_LLD_LINK FALSE)
 endif()
 
 set(LLVM_CXX_STD_default "c++11")
 # Preserve behaviour of legacy cache variables
 if (LLVM_ENABLE_CXX1Y)
if (NOT MSVC)
     endif()
     # Use -O1 even in debug mode, otherwise sanitizers slowdown is too large.
     if (uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG" AND LLVM_OPTIMIZE_SANITIZED_BUILDS)
       add_flag_if_supported("-O1" O1)
     endif()
   elseif (CLANG_CL)
     # Keep frame pointers around.
     append("/Oy-" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
-    if (LINKER_IS_LLD_LINK)
-      # Use DWARF debug info with LLD.
-      append("-gdwarf" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
-    else()
-      # Enable codeview otherwise.
-      append("/Z7" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
-    endif()
     # Always ask the linker to produce symbols with asan.
+    append("/Z7" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
     append("-debug" CMAKE_EXE_LINKER_FLAGS CMAKE_MODULE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS)
   endif()
 endmacro()
 
 # Turn on sanitizers if necessary.
 if(LLVM_USE_SANITIZER)
   if (LLVM_ON_UNIX)
     if (LLVM_USE_SANITIZER STREQUAL "Address")