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

[mstorsjo]

Summary

This is modelled after how the ELF driver does it; 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
https://github.com/mstorsjo/llvm-mingw/issues/349.

[MaskRay]

Consider linking to D78158 in the summary for more context.

lld/test/MinGW/driver.test

380

Test that we ignore -plugin-opt=...lto-wrapper.exe as well. If lto-wrapper.exe is not present, remove the special case !v.ends_with("lto-wrapper.exe")

[mstorsjo]

In D158412#4604933, @MaskRay wrote:

Consider linking to D78158 in the summary for more context.

Thanks for the reference, I'll include that!

lld/test/MinGW/driver.test

380

Ok, I'll include a sample with what it looks like on Windows as well.

[mstorsjo]

Amended the test with samples of GCC passed options from Windows too, silence the test lines that don't use FileCheck.

[mati865]

LGTM

[MaskRay]

lld/test/MinGW/driver.test

381

backslashes may need quotes to prevent problems.

[mstorsjo]

lld/test/MinGW/driver.test

381

Oh, I missed that there were some backslashes, I'll change them to forward slashes.

[mstorsjo]

@MaskRay How do you feel about backporting a change like this, and the associated one in D158411? It's not a regression fix or something like that, but fairly simple added value.

[MaskRay]

In D158412#4614970, @mstorsjo wrote:

@MaskRay How do you feel about backporting a change like this, and the associated one in D158411? It's not a regression fix or something like that, but fairly simple added value.

LGTM for back porting

[mstorsjo]

In D158412#4615043, @MaskRay wrote:

In D158412#4614970, @mstorsjo wrote:

@MaskRay How do you feel about backporting a change like this, and the associated one in D158411? It's not a regression fix or something like that, but fairly simple added value.

LGTM for back porting

Actually, I think I'll hold off of backporting this one. My nightly testing uncovered some cases that broke due to this; if I call e.g. clang -O2 main.c -o out -flto, it passes -plugin-opt=O2 which we don't handle yet, and likewise -flto=thin passes -plugin-opt=thinlto, which also isn't handled (while the ELF linker driver just ignores it).

I tried to look through what LTO options the lld-link interface supports and what options that Clang can end up passing automatically in addLTOOptions, and add at least those (the ELF driver supports lots and lots of LTO options, but I didn't try to include all of them yet). I'll send another patch with that soon.

lld/MinGW/Driver.cpp

if (s.getAsInteger(10, n))
       error(a->getSpelling() + ": number expected, but got " + s);
     else
       add("-errorlimit:" + s);
   }
 
   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());
 
   if (args.getLastArgValue(OPT_m) == "i386pe")
     add("-alternatename:__image_base__=___ImageBase");
   else
     add("-alternatename:__image_base__=__ImageBase");
 

lld/MinGW/Options.td

defm whole_archive: B<"whole-archive",
     "Include all object files for following archives",
     "No longer include all object files for following archives">;
 def v: Flag<["-"], "v">, HelpText<"Display the version number">;
 def verbose: F<"verbose">, HelpText<"Verbose mode">;
 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">;
 def appcontainer: F<"appcontainer">, HelpText<"Set the appcontainer flag in the executable">;
 defm delayload: Eq<"delayload", "DLL to load only on demand">;
 defm mllvm: EqNoHelp<"mllvm">;
 defm pdb: Eq<"pdb", "Output PDB debug info file, chosen implicitly if the argument is empty">;
 defm thinlto_cache_dir: EqLong<"thinlto-cache-dir",

 def: F<"enable-auto-image-base">;
 def: F<"end-group">;
 def: Flag<["--"], "full-shutdown">;
 defm: EqNoHelp<"major-image-version">;
 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

 GUARD_CF: -guard:cf,longjmp
 
 RUN: ld.lld -### foo.o -m i386pep --guard-cf --no-guard-longjmp 2>&1 | FileCheck -check-prefix=GUARD_CF_NOLONGJMP %s
 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