[LinkerWrapper] Accept some needed lld-link linker arguments for COFF targets (#72889)

Summary:
The linker wrapper is a utility used to create offloading programs from
single-source offloading languages such as OpenMP or CUDA. This is done
by embedding device code into the host object, then feeding it into the
linker wrapper which extracts the accelerator object files, links them,
then wraps them in registration code for the target  runtime. This
previously has only worked in Linux / ELF platforms.

This patch attempts to hand Windows / COFF inputs by also accepting COFF
forms of certain linker arguments we use internally. The important
arguments are library search paths, so we can identify libraries which
may contain device code, libraries themselves, and the output name used
for intermediate output.

I am not intimately familiar with the semantics here for the semantics
in how a `lib` file is earched. I am simply treating `foo.lib` as the
GNU equivalent `-l:foo.lib` in the search logic. Similarly, I am
assuming that static libraries will be llvm-ar style libraries. I will
need to investigate the actual deficiencies later, but this should be a
good starting point along with
#72697

Author: jhuber6

clang/test/Driver/linker-wrapper.c

@@ -140,3 +140,11 @@
 // RUN:   --linker-path=/usr/bin/ld -- %t.o -o a.out 2>&1 | FileCheck %s --check-prefix=CLANG-BACKEND
 
 // CLANG-BACKEND: clang{{.*}} -o {{.*}}.img --target=amdgcn-amd-amdhsa -mcpu=gfx908 -O2 -Wl,--no-undefined {{.*}}.bc
+
+// RUN: clang-offload-packager -o %t.out \
+// RUN:   --image=file=%t.elf.o,kind=openmp,triple=nvptx64-nvidia-cuda,arch=sm_70
+// RUN: %clang -cc1 %s -triple x86_64-unknown-windows-msvc -emit-obj -o %t.o -fembed-offload-object=%t.out
+// RUN: clang-linker-wrapper --host-triple=x86_64-unknown-windows-msvc --dry-run \
+// RUN:   --linker-path=/usr/bin/lld-link -- %t.o -libpath:./ -out:a.exe 2>&1 | FileCheck %s --check-prefix=COFF
+
+// COFF: "/usr/bin/lld-link" {{.*}}.o -libpath:./ -out:a.exe {{.*}}openmp.image.wrapper{{.*}}

clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp

@@ -254,7 +254,7 @@ Error runLinker(ArrayRef<StringRef> Files, const ArgList &Args) {
       continue;
 
     Arg->render(Args, NewLinkerArgs);
-    if (Arg->getOption().matches(OPT_o))
+    if (Arg->getOption().matches(OPT_o) || Arg->getOption().matches(OPT_out))
       llvm::transform(Files, std::back_inserter(NewLinkerArgs),
                       [&](StringRef Arg) { return Args.MakeArgString(Arg); });
   }
@@ -1188,7 +1188,7 @@ searchLibraryBaseName(StringRef Name, StringRef Root,
 /// `-lfoo` or `-l:libfoo.a`.
 std::optional<std::string> searchLibrary(StringRef Input, StringRef Root,
                                          ArrayRef<StringRef> SearchPaths) {
-  if (Input.startswith(":"))
+  if (Input.startswith(":") || Input.ends_with(".lib"))
     return findFromSearchPaths(Input.drop_front(), Root, SearchPaths);
   return searchLibraryBaseName(Input, Root, SearchPaths);
 }
@@ -1339,7 +1339,7 @@ Expected<SmallVector<OffloadFile>> getDeviceInput(const ArgList &Args) {
 
   StringRef Root = Args.getLastArgValue(OPT_sysroot_EQ);
   SmallVector<StringRef> LibraryPaths;
-  for (const opt::Arg *Arg : Args.filtered(OPT_library_path))
+  for (const opt::Arg *Arg : Args.filtered(OPT_library_path, OPT_libpath))
     LibraryPaths.push_back(Arg->getValue());
 
   BumpPtrAllocator Alloc;
@@ -1348,7 +1348,7 @@ Expected<SmallVector<OffloadFile>> getDeviceInput(const ArgList &Args) {
   // Try to extract device code from the linker input files.
   SmallVector<OffloadFile> InputFiles;
   DenseMap<OffloadFile::TargetID, DenseMap<StringRef, Symbol>> Syms;
-  bool WholeArchive = false;
+  bool WholeArchive = Args.hasArg(OPT_wholearchive_flag) ? true : false;
   for (const opt::Arg *Arg : Args.filtered(
            OPT_INPUT, OPT_library, OPT_whole_archive, OPT_no_whole_archive)) {
     if (Arg->getOption().matches(OPT_whole_archive) ||
@@ -1474,9 +1474,17 @@ int main(int Argc, char **Argv) {
   Verbose = Args.hasArg(OPT_verbose);
   DryRun = Args.hasArg(OPT_dry_run);
   SaveTemps = Args.hasArg(OPT_save_temps);
-  ExecutableName = Args.getLastArgValue(OPT_o, "a.out");
   CudaBinaryPath = Args.getLastArgValue(OPT_cuda_path_EQ).str();
 
+  llvm::Triple Triple(
+      Args.getLastArgValue(OPT_host_triple_EQ, sys::getDefaultTargetTriple()));
+  if (Args.hasArg(OPT_o))
+    ExecutableName = Args.getLastArgValue(OPT_o, "a.out");
+  else if (Args.hasArg(OPT_out))
+    ExecutableName = Args.getLastArgValue(OPT_out, "a.exe");
+  else
+    ExecutableName = Triple.isOSWindows() ? "a.exe" : "a.out";
+
   parallel::strategy = hardware_concurrency(1);
   if (auto *Arg = Args.getLastArg(OPT_wrapper_jobs)) {
     unsigned Threads = 0;

clang/tools/clang-linker-wrapper/LinkerWrapperOpts.td

@@ -126,3 +126,8 @@ def version : Flag<["--", "-"], "version">, Flags<[HelpHidden]>, Alias<v>;
 
 def whole_archive : Flag<["--", "-"], "whole-archive">, Flags<[HelpHidden]>;
 def no_whole_archive : Flag<["--", "-"], "no-whole-archive">, Flags<[HelpHidden]>;
+
+// link.exe-style linker options.
+def out : Joined<["/", "-", "/?", "-?"], "out:">, Flags<[HelpHidden]>;
+def libpath : Joined<["/", "-", "/?", "-?"], "libpath:">, Flags<[HelpHidden]>;
+def wholearchive_flag : Joined<["/", "-", "/?", "-?"], "wholearchive">, Flags<[HelpHidden]>;