[COFF] Add parsing of mllvm command line options.

[alberto_magni]

Summary

Original patch by Kyungwoo Lee <[e-mail]>

[ruiu]

LGTM

[alberto_magni]

I don't have commit access.
@ruiu can you please commit it ?
Thanks

[ruiu]

But this needs testcase. Do you have one?

[alberto_magni]

I can prepare one.
I am thinking about a test that uses mllvm to forward -time-passes, similarly to what ELF/lto/timepasses.ll does.
Would that be ok for you ?

[ruiu]

Yes, I think that is fine.

[alberto_magni]

Added test case for mllvm option.

My original idea was to test mllvm using the -time-passes option.
It turns out that lld-link does not perfom a full shutdown (and there is no -full-shutdown option available) when exiting.
So I opted for passing -debug-pass=Arguments and checking for the output string: "Pass Arguments:".

lld/trunk/COFF/Driver.cpp

void LinkerDriver::link(ArrayRef<const char *> ArgsArr) {
   InitializeAllTargetMCs();
   InitializeAllAsmParsers();
   InitializeAllAsmPrinters();
   InitializeAllDisassemblers();
 
   // Parse command line options.
   opt::InputArgList Args = Parser.parseLINK(ArgsArr.slice(1));
 
+  // Parse and evaluate -mllvm options.
+  std::vector<const char *> V;
+  V.push_back("lld-link (LLVM option parsing)");
+  for (auto *Arg : Args.filtered(OPT_mllvm))
+    V.push_back(Arg->getValue());
+  cl::ParseCommandLineOptions(V.size(), V.data());
+
   // Handle /help
   if (Args.hasArg(OPT_help)) {
     printHelp(ArgsArr[0]);
     return;
   }
 
   if (auto *Arg = Args.getLastArg(OPT_linkrepro)) {
     SmallString<64> Path = StringRef(Arg->getValue());

lld/trunk/test/COFF/lto-debug-pass-arguments.ll

+; REQUIRES: x86
+; RUN: llvm-as %s -o %t.obj
+; RUN: lld-link /dll /out:%t.dll %t.obj /mllvm:-debug-pass=Arguments 2>&1 | FileCheck %s
+
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc"
+
+define void @dummy() {
+  ret void
+}
+
+define void @_DllMainCRTStartup() {
+  ret void
+}
+
+; CHECK: Pass Arguments: