[LLD] [MinGW] Pass libpath to the COFF linker

[mstorsjo]

Summary

This is necessary for handling defaultlib directives embedded in object files, unless they use an absolute path.

This is needed in all incarnations of D53012 and regardless of whether D53013 is picked or not.

[ruiu]

If you do this, do you still have to search library files in MinGW driver?

[mstorsjo]

In D53015#1258758, @ruiu wrote:

If you do this, do you still have to search library files in MinGW driver?

Yes, we still need to keep it there.

In order to move all of that into the COFF linker side, we'd need to extend the lld-link command line interface quite a bit. The MinGW linker takes -lfoo, which can either mean libfoo.a or libfoo.dll.a (unless the -Bstatic flag was passed). As lld-link today only takes full filenames, this doesn't fit right away as is. And we'd need the static flag of course. And the static flag isn't global but only affects any later -lfoo up until the next -Bdynamic.

[ruiu]

LGTM

lld/trunk/MinGW/Driver.cpp

if (Args.getLastArgValue(OPT_m) == "i386pe")
     Add("-alternatename:__image_base__=___ImageBase");
   else
     Add("-alternatename:__image_base__=__ImageBase");
 
   for (auto *A : Args.filtered(OPT_require_defined))
     Add("-include:" + StringRef(A->getValue()));
 
   std::vector<StringRef> SearchPaths;
-  for (auto *A : Args.filtered(OPT_L))
+  for (auto *A : Args.filtered(OPT_L)) {
     SearchPaths.push_back(A->getValue());
+    Add("-libpath:" + StringRef(A->getValue()));
+  }
 
   StringRef Prefix = "";
   bool Static = false;
   for (auto *A : Args) {
     switch (A->getOption().getUnaliasedOption().getID()) {
     case OPT_INPUT:
       if (StringRef(A->getValue()).endswith_lower(".def"))
         Add("-def:" + StringRef(A->getValue()));

lld/trunk/test/MinGW/driver.test

 RUN: ld.lld -### foo.o -m i386pep -Map bar.map | FileCheck -check-prefix=MAP %s
 RUN: ld.lld -### foo.o -m i386pep --Map bar.map | FileCheck -check-prefix=MAP %s
 RUN: ld.lld -### foo.o -m i386pep -Map=bar.map | FileCheck -check-prefix=MAP %s
 RUN: ld.lld -### foo.o -m i386pep --Map=bar.map | FileCheck -check-prefix=MAP %s
 MAP: -lldmap:bar.map
 
 RUN: ld.lld -### foo.o -m i386pe -require-defined _foo --require-defined _bar -require-defined=_baz --require-defined=_foo2 | FileCheck -check-prefix=REQUIRE-DEFINED %s
 REQUIRE-DEFINED: -include:_foo -include:_bar -include:_baz -include:_foo2
+
+RUN: ld.lld -### -m i386pep foo.o -Llibpath | FileCheck -check-prefix LIBPATH %s
+LIBPATH: -libpath:libpath