[LLD] [MinGW] Pass LLVM specific LTO options through to lld-link

This is modelled after how the ELF driver does it (see e.g.
https://reviews.llvm.org/D78158 for the source of the ELF
implementation); we need to intercept some options, but ignore GCC
specific ones that GCC passes regardless of whether GCC is using
LTO or not.

This is the second part of the fix for
mstorsjo/llvm-mingw#349.

Differential Revision: https://reviews.llvm.org/D158412

Author: mstorsjo

lld/MinGW/Driver.cpp

@@ -418,6 +418,23 @@ bool link(ArrayRef<const char *> argsArr, llvm::raw_ostream &stdoutOS,
   for (auto *a : args.filtered(OPT_mllvm))
     add("-mllvm:" + StringRef(a->getValue()));
 
+  if (auto *arg = args.getLastArg(OPT_plugin_opt_mcpu_eq))
+    add("-mllvm:-mcpu=" + StringRef(arg->getValue()));
+
+  for (auto *a : args.filtered(OPT_plugin_opt_eq_minus))
+    add("-mllvm:-" + StringRef(a->getValue()));
+
+  // GCC collect2 passes -plugin-opt=path/to/lto-wrapper with an absolute or
+  // relative path. Just ignore. If not ended with "lto-wrapper" (or
+  // "lto-wrapper.exe" for GCC cross-compiled for Windows), consider it an
+  // unsupported LLVMgold.so option and error.
+  for (opt::Arg *arg : args.filtered(OPT_plugin_opt_eq)) {
+    StringRef v(arg->getValue());
+    if (!v.ends_with("lto-wrapper") && !v.ends_with("lto-wrapper.exe"))
+      error(arg->getSpelling() + ": unknown plugin option '" + arg->getValue() +
+            "'");
+  }
+
   for (auto *a : args.filtered(OPT_Xlink))
     add(a->getValue());
 

lld/MinGW/Options.td

@@ -131,6 +131,13 @@ def version: F<"version">, HelpText<"Display the version number and exit">;
 defm wrap: Eq<"wrap", "Use wrapper functions for symbol">,
      MetaVarName<"<symbol>">;
 
+def plugin_opt_eq_minus: J<"plugin-opt=-">,
+  HelpText<"Specify an LLVM option for compatibility with LLVMgold.so">;
+def plugin_opt_mcpu_eq: J<"plugin-opt=mcpu=">;
+// This may be either an unhandled LLVMgold.so feature or GCC passed
+// -plugin-opt=path/to/{liblto_plugin.so,lto-wrapper}
+def plugin_opt_eq : J<"plugin-opt=">;
+
 // LLD specific options
 def _HASH_HASH_HASH : Flag<["-"], "###">,
     HelpText<"Print (but do not run) the commands to run for this compilation">;
@@ -174,6 +181,10 @@ defm: EqNoHelp<"minor-image-version">;
 def: F<"no-undefined">;
 def: F<"pic-executable">;
 defm: EqNoHelp<"plugin">;
-defm: EqNoHelp<"plugin-opt">;
 defm: EqNoHelp<"sysroot">;
 def: F<"start-group">;
+
+// Ignore GCC collect2 LTO plugin related options. Note that we don't support
+// GCC LTO, but GCC collect2 passes these options even in non-LTO mode.
+def: J<"plugin-opt=-fresolution=">;
+def: J<"plugin-opt=-pass-through=">;

lld/test/MinGW/driver.test

@@ -371,3 +371,11 @@ GUARD_CF_NOLONGJMP: -guard:cf,nolongjmp
 RUN: ld.lld -### foo.o -m i386pep --guard-longjmp 2>&1 | FileCheck -check-prefix=GUARD_LONGJMP_NO_CF %s
 RUN: ld.lld -### foo.o -m i386pep --no-guard-cf --guard-longjmp 2>&1 | FileCheck -check-prefix=GUARD_LONGJMP_NO_CF %s
 GUARD_LONGJMP_NO_CF: warning: parameter --guard-longjmp only takes effect when used with --guard-cf
+
+RUN: ld.lld -### foo.o -m i386pep -plugin-opt=mcpu=x86-64 -plugin-opt=-emulated-tls 2>&1 | FileCheck -check-prefix=LTO_OPTS %s
+LTO_OPTS: -mllvm:-mcpu=x86-64 -mllvm:-emulated-tls
+
+Test GCC specific LTO options that GCC passes unconditionally, that we ignore.
+
+RUN: ld.lld -### foo.o -m i386pep -plugin /usr/lib/gcc/x86_64-w64-mingw32/10-posix/liblto_plugin.so -plugin-opt=/usr/lib/gcc/x86_64-w64-mingw32/10-posix/lto-wrapper -plugin-opt=-fresolution=/tmp/ccM9d4fP.res -plugin-opt=-pass-through=-lmingw32 2> /dev/null
+RUN: ld.lld -### foo.o -m i386pep -plugin C:/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/13.2.0/liblto_plugin.dll -plugin-opt=C:/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/13.2.0/lto-wrapper.exe -plugin-opt=-fresolution=C:/msys64/tmp/cckbC7wB.res -plugin-opt=-pass-through=-lmingw32 2> /dev/null