[LinkerWrapper] Forward -mllvm and --offload-opt arguments to device (#100424)

Summary:
Previously we could parse these internally as they would be used by the
embedded LTO job. Now, this LTO is passed to the linker utilities which
means these need to be forwarded. So this can now either be done with
`--offload-opt` which works in the clang job, or with `-Xoffload-linker`
manually.

Fixes #100212

Author: jhuber6

clang/test/Driver/linker-wrapper.c

@@ -234,3 +234,13 @@ __attribute__((visibility("protected"), used)) int x;
 // RUN: | FileCheck %s --check-prefix=OVERRIDE
 // OVERRIDE-NOT: clang
 // OVERRIDE: /usr/bin/ld
+
+// RUN: clang-offload-packager -o %t.out \
+// RUN:   --image=file=%t.elf.o,kind=openmp,triple=amdgcn-amd-amdhsa,arch=gfx908
+// RUN: %clang -cc1 %s -triple x86_64-unknown-linux-gnu -emit-obj -o %t.o -fembed-offload-object=%t.out
+// RUN: clang-linker-wrapper --host-triple=x86_64-unknown-linux-gnu --dry-run --offload-opt=-pass-remarks=foo \
+// RUN:   --linker-path=/usr/bin/ld %t.o -o a.out 2>&1 | FileCheck %s --check-prefix=OFFLOAD-OPT
+// RUN: clang-linker-wrapper --host-triple=x86_64-unknown-linux-gnu --dry-run -mllvm -pass-remarks=foo \
+// RUN:   --linker-path=/usr/bin/ld %t.o -o a.out 2>&1 | FileCheck %s --check-prefix=OFFLOAD-OPT
+
+// OFFLOAD-OPT: clang{{.*}}-Wl,--plugin-opt=-pass-remarks=foo

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

@@ -297,7 +297,8 @@ Expected<std::string> findProgram(StringRef Name, ArrayRef<StringRef> Paths) {
 /// supported by the toolchain.
 bool linkerSupportsLTO(const ArgList &Args) {
   llvm::Triple Triple(Args.getLastArgValue(OPT_triple_EQ));
-  return Triple.isNVPTX() || Triple.isAMDGPU();
+  return Triple.isNVPTX() || Triple.isAMDGPU() ||
+         Args.getLastArgValue(OPT_linker_path_EQ).ends_with("ld.lld");
 }
 
 /// Returns the hashed value for a constant string.
@@ -524,6 +525,13 @@ Expected<StringRef> clang(ArrayRef<StringRef> InputFiles, const ArgList &Args) {
       Args.MakeArgString("-" + OptLevel),
   };
 
+  // Forward all of the `--offload-opt` and similar options to the device.
+  if (linkerSupportsLTO(Args)) {
+    for (auto &Arg : Args.filtered(OPT_offload_opt_eq_minus, OPT_mllvm))
+      CmdArgs.push_back(
+          Args.MakeArgString("-Wl,--plugin-opt=" + StringRef(Arg->getValue())));
+  }
+
   if (!Triple.isNVPTX())
     CmdArgs.push_back("-Wl,--no-undefined");
 
@@ -1756,7 +1764,7 @@ int main(int Argc, char **Argv) {
   for (const opt::Arg *Arg : Args.filtered(OPT_mllvm))
     NewArgv.push_back(Arg->getValue());
   for (const opt::Arg *Arg : Args.filtered(OPT_offload_opt_eq_minus))
-    NewArgv.push_back(Args.MakeArgString(StringRef("-") + Arg->getValue()));
+    NewArgv.push_back(Arg->getValue());
   SmallVector<PassPlugin, 1> PluginList;
   PassPlugins.setCallback([&](const std::string &PluginPath) {
     auto Plugin = PassPlugin::Load(PluginPath);

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

@@ -98,7 +98,7 @@ def mllvm : Separate<["-"], "mllvm">, Flags<[WrapperOnlyOption]>,
   HelpText<"Arguments passed to LLVM, including Clang invocations, for which "
            "the '-mllvm' prefix is preserved. Use '-mllvm --help' for a list "
            "of options.">;
-def offload_opt_eq_minus : Joined<["--", "-"], "offload-opt=-">, Flags<[HelpHidden, WrapperOnlyOption]>,
+def offload_opt_eq_minus : Joined<["--", "-"], "offload-opt=">, Flags<[HelpHidden, WrapperOnlyOption]>,
   HelpText<"Options passed to LLVM, not including the Clang invocation. Use "
            "'--offload-opt=--help' for a list of options.">;