clang-cl: Pass /Brepro to linker if it was passed to the compiler

[thakis]

Summary

/Brepro currently is just an alias for -mno-incremental-linker-compatible and before this patch only controlled if we write a timestamp into the output obj file. But cl.exe also passes it on to link.exe (where it controls whether the final PE image timestamp really is a timestamp or a hash of the output).

It's a bit weird to overload -mno-incremental-linker-compatible to also pass /Brepro to the linker, but all alternatives are a bit weird too. Open for suggestions though :-)

[hans]

I suppose the alternative would be to make /Brepro a non-alias flag, expand it to -mno-incremental-linker-compatible for the cc1 invocation and look for it for the linker invocation.

But this is fine too.

lib/Driver/ToolChains/MSVC.cpp

for (const auto &LibPath : Args.getAllArgValues(options::OPT_L))
       CmdArgs.push_back(Args.MakeArgString("-libpath:" + LibPath));
 
   CmdArgs.push_back("-nologo");
 
   if (Args.hasArg(options::OPT_g_Group, options::OPT__SLASH_Z7,
                   options::OPT__SLASH_Zd))
     CmdArgs.push_back("-debug");
 
+  // Pass on /Brepro if it was passed to the compiler.
+  // Note that /Brepro maps to -mno-incremental-linker-compatible.
+  bool DefaultIncrementalLinkerCompatible =
+      C.getDefaultToolChain().getTriple().isWindowsMSVCEnvironment();
+  if (!Args.hasFlag(options::OPT_mincremental_linker_compatible,
+                    options::OPT_mno_incremental_linker_compatible,
+                    DefaultIncrementalLinkerCompatible))
+    CmdArgs.push_back("-Brepro");
+
   bool DLL = Args.hasArg(options::OPT__SLASH_LD, options::OPT__SLASH_LDd,
                          options::OPT_shared);
   if (DLL) {
     CmdArgs.push_back(Args.MakeArgString("-dll"));
 
     SmallString<128> ImplibName(Output.getFilename());
     llvm::sys::path::replace_extension(ImplibName, "lib");
     CmdArgs.push_back(Args.MakeArgString(std::string("-implib:") + ImplibName));

test/Driver/msvc-link.c

 // RUN: %clang -target i686-pc-windows-msvc -### %s 2>&1 | FileCheck --check-prefix=BASIC %s
 // BASIC: link.exe"
 // BASIC: "-out:a.exe"
 // BASIC: "-defaultlib:libcmt"
 // BASIC: "-nologo"
+// BASIC-NOT: "-Brepro"
 
 // RUN: %clang -target i686-pc-windows-msvc -shared -o a.dll -### %s 2>&1 | FileCheck --check-prefix=DLL %s
 // DLL: link.exe"
 // DLL: "-out:a.dll"
 // DLL: "-defaultlib:libcmt"
 // DLL: "-nologo"
 // DLL: "-dll"
 
 // RUN: %clang -target i686-pc-windows-msvc -L/var/empty -L/usr/lib -### %s 2>&1 | FileCheck --check-prefix LIBPATH %s
 // LIBPATH: "-libpath:/var/empty"
 // LIBPATH: "-libpath:/usr/lib"
 // LIBPATH: "-nologo"
 
+// RUN: %clang_cl /Brepro -### %s 2>&1 | FileCheck --check-prefix=REPRO %s
+// REPRO: link.exe"
+// REPRO: "-out:msvc-link.exe"
+// REPRO: "-nologo"
+// REPRO: "-Brepro"
+
+// RUN: %clang_cl /Brepro- -### %s 2>&1 | FileCheck --check-prefix=NOREPRO %s
+// NOREPRO: link.exe"
+// NOREPRO: "-out:msvc-link.exe"
+// NOREPRO: "-nologo"
+// NOREPRO-NOT: "-Brepro"