[CMake] Fixes /INCREMENTAL detection when considering adding /Brepro

[ychen]

Summary

/INCREMENTAL is the linker default (lld-link and MSVC link). Specifying
"/INCREMENTAL:NO" is the only way to disable it. So checking for the
negative flag instead and check exe/module/shared link flags
independently.

[rnk]

lgtm

llvm/cmake/modules/HandleLLVMOptions.cmake

if (C_SUPPORTS_${name} AND CXX_SUPPORTS_${name})
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${flag}" PARENT_SCOPE)
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${flag}" PARENT_SCOPE)
     set(CMAKE_ASM_FLAGS "${CMAKE_ASM_FLAGS} ${flag}" PARENT_SCOPE)
   else()
     message(WARNING "${flag} is not supported.")
   endif()
 endfunction()
 
+function(has_msvc_incremental_no_flag flags incr_no_flag_on)
+  set(${incr_no_flag_on} OFF PARENT_SCOPE)
+  string(FIND "${flags}" "/INCREMENTAL" idx REVERSE)
+  if (${idx} GREATER -1)
+    string(SUBSTRING "${flags}" ${idx} 15 no_flag)
+    if (${no_flag} MATCHES "/INCREMENTAL:NO")
+      set(${incr_no_flag_on} ON PARENT_SCOPE)
+    endif()
+  endif()
+endfunction()
+
 if( LLVM_ENABLE_LLD )
   if ( LLVM_USE_LINKER )
     message(FATAL_ERROR "LLVM_ENABLE_LLD and LLVM_USE_LINKER can't be set at the same time")
   endif()
   # In case of MSVC cmake always invokes the linker directly, so the linker
   # should be specified by CMAKE_LINKER cmake variable instead of by -fuse-ld
   # compiler option.
   if ( NOT MSVC )
if (CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND NOT LLVM_ENABLE_LTO)
     # being unused, because we're not generating object files).
     # This checks CMAKE_CXX_COMPILER_ID in addition to check_cxx_compiler_flag()
     # because cl.exe does not emit an error on flags it doesn't understand,
     # letting check_cxx_compiler_flag() claim it understands all flags.
     check_cxx_compiler_flag("/Brepro" SUPPORTS_BREPRO)
     if (SUPPORTS_BREPRO)
       # Check if /INCREMENTAL is passed to the linker and complain that it
       # won't work with /Brepro.
-      string(FIND "${all_linker_flags_uppercase}" "/INCREMENTAL" linker_flag_idx)
-      if (${linker_flag_idx} GREATER -1)
-        message(WARNING "/Brepro not compatible with /INCREMENTAL linking - builds will be non-deterministic")
-      else()
+      has_msvc_incremental_no_flag("${CMAKE_EXE_LINKER_FLAGS_${uppercase_CMAKE_BUILD_TYPE}} ${CMAKE_EXE_LINKER_FLAGS}" NO_INCR_EXE)
+      has_msvc_incremental_no_flag("${CMAKE_MODULE_LINKER_FLAGS_${uppercase_CMAKE_BUILD_TYPE}} ${CMAKE_MODULE_LINKER_FLAGS}" NO_INCR_MODULE)
+      has_msvc_incremental_no_flag("${CMAKE_SHARED_LINKER_FLAGS_${uppercase_CMAKE_BUILD_TYPE}} ${CMAKE_SHARED_LINKER_FLAGS}" NO_INCR_SHARED)
+      if (NO_INCR_EXE AND NO_INCR_MODULE AND NO_INCR_SHARED)
         append("/Brepro" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+      else()
+        message(WARNING "/Brepro not compatible with /INCREMENTAL linking - builds will be non-deterministic")
       endif()
     endif()
   endif()
   # By default MSVC has a 2^16 limit on the number of sections in an object file,
   # but in many objects files need more than that. This flag is to increase the
   # number of sections.
   append("/bigobj" CMAKE_CXX_FLAGS)
 endif( MSVC )