Make WinCOFFObjectWriter.cpp's timestamp writing not use ENABLE_TIMESTAMPS

LLVM_ENABLE_TIMESTAMPS controls if timestamps are embedded into llvm's
binaries. Turning it off is useful for deterministic builds.

r246905 made it so that the define suddenly also controls if the binaries that
the llvm binaries _create_ embed timestamps or not – but this shouldn't be a
configure-time option. r256203/r256204 added a driver option to toggle this on
and off, so this patch now passes this driver option in LLVM_ENABLE_TIMESTAMPS
builds so that if LLVM_ENABLE_TIMESTAMPS is set, the build of LLVM is
deterministic – but the built clang can still write timestamps into other
executables when requested.

This also allows removing some of the test machinery added in r292012 to work
around this problem.

See PR24740 for background.
http://reviews.llvm.org/D15783

llvm-svn: 256958

cmake/modules/HandleLLVMOptions.cmake

@@ -363,6 +363,36 @@ if( MSVC )
 
   append("/Zc:inline" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
 
+  if (NOT LLVM_ENABLE_TIMESTAMPS AND CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+    # clang-cl and cl by default produce non-deterministic binaries because
+    # link.exe /incremental requires a timestamp in the .obj file.  clang-cl
+    # has the flag /Brepro to force deterministic binaries, so pass that when
+    # LLVM_ENABLE_TIMESTAMPS is turned off.
+    # 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)
+    append_if(SUPPORTS_BREPRO "/Brepro" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+
+    if (SUPPORTS_BREPRO)
+      # Check if /INCREMENTAL is passed to the linker and complain that it
+      # won't work with /Brepro.
+      string(TOUPPER "${CMAKE_EXE_LINKER_FLAGS}" upper_exe_flags)
+      string(TOUPPER "${CMAKE_MODULE_LINKER_FLAGS}" upper_module_flags)
+      string(TOUPPER "${CMAKE_SHARED_LINKER_FLAGS}" upper_shared_flags)
+
+      string(FIND "${upper_exe_flags}" "/INCREMENTAL" exe_index)
+      string(FIND "${upper_module_flags}" "/INCREMENTAL" module_index)
+      string(FIND "${upper_shared_flags}" "/INCREMENTAL" shared_index)
+      
+      if (${exe_index} GREATER -1 OR
+          ${module_index} GREATER -1 OR
+          ${shared_index} GREATER -1)
+        message(FATAL_ERROR "LLVM_ENABLE_TIMESTAMPS not compatible with /INCREMENTAL linking")
+      endif()
+    endif()
+  endif()
+
   # Disable sized deallocation if the flag is supported. MSVC fails to compile
   # the operator new overload in User otherwise.
   check_c_compiler_flag("/WX /Zc:sizedDealloc-" SUPPORTS_SIZED_DEALLOC)

lib/MC/WinCOFFObjectWriter.cpp

@@ -969,9 +969,6 @@ void WinCOFFObjectWriter::writeObject(MCAssembler &Asm,
 
   Header.PointerToSymbolTable = offset;
 
-  // FIXME: Remove the #else branch and make the #if branch unconditional once
-  // LLVM's self host configuration is aware of /Brepro.
-#if (ENABLE_TIMESTAMPS == 1)
   // MS LINK expects to be able to use this timestamp to implement their
   // /INCREMENTAL feature.
   if (Asm.isIncrementalLinkerCompatible()) {
@@ -980,12 +977,9 @@ void WinCOFFObjectWriter::writeObject(MCAssembler &Asm,
       Now = UINT32_MAX;
     Header.TimeDateStamp = Now;
   } else {
+    // Have deterministic output if /INCREMENTAL isn't needed. Also matches GNU.
     Header.TimeDateStamp = 0;
   }
-#else
-  // We want a deterministic output. It looks like GNU as also writes 0 in here.
-  Header.TimeDateStamp = 0;
-#endif
 
   // Write it all to disk...
   WriteFileHeader(Header);

test/MC/COFF/timestamp.s

@@ -1,5 +1,4 @@
 // RUN: llvm-mc -filetype=obj -triple i686-pc-win32 -incremental-linker-compatible %s -o - | llvm-readobj -h | FileCheck %s
-// REQUIRES: timestamps
 
 // CHECK: ImageFileHeader {
 // CHECK:   TimeDateStamp:

test/lit.cfg

@@ -459,10 +459,6 @@ if platform.system() in ['Windows'] and re.match(r'.*-win32$', config.target_tri
 if not re.match(r'^x86_64.*-(mingw32|windows-gnu|win32)', config.target_triple):
     config.available_features.add('debug_frame')
 
-# Check if we are embedding timestamps.
-if config.enable_timestamps == '1':
-    config.available_features.add('timestamps')
-
 # Check if we should use gmalloc.
 use_gmalloc_str = lit_config.params.get('use_gmalloc', None)
 if use_gmalloc_str is not None:

test/lit.site.cfg.in

@@ -36,7 +36,6 @@ config.llvm_use_sanitizer = "@LLVM_USE_SANITIZER@"
 config.have_zlib = "@HAVE_LIBZ@"
 config.have_dia_sdk = @HAVE_DIA_SDK@
 config.enable_ffi = "@LLVM_ENABLE_FFI@"
-config.enable_timestamps = "@ENABLE_TIMESTAMPS@"
 config.test_examples = "@ENABLE_EXAMPLES@"
 
 # Support substitution of the tools_dir with user parameters. This is