[ELF] - Process R_X86_64_GOTPCRELX/R_X86_64_REX_GOTPCRELX relocations.

[grimar]

Summary

That should fix the Bug 26995 - [regression] unrecognized reloc 42 (https://llvm.org/bugs/show_bug.cgi?id=26995).

R_X86_64_GOTPCRELX and R_X86_64_REX_GOTPCRELX relocations were added in latest ABI:
https://github.com/hjl-tools/x86-psABI/wiki/x86-64-psABI-r249.pdf

They should be generated instead of R_X86_64_GOTPCREL for cases when relaxation is possible.
Currently this patch just process them in the same way like R_X86_64_GOTPCREL. That should work for now
and we can implement relaxations later.

Patch implementing relaxations was posted before and on review now (http://reviews.llvm.org/D15779).

There is no testcases provided as I think there is no way to generate such relocations using llvm-mc atm.

[grimar]

Correct. Normally I would ask for a binary testcase, but given that we
will probably want to change llvm-mc to produce them and lld to
optimized, LGTM for now.

Ok, thank you, I will commit that tomorrow then (If nothing changes).

Cheers,
Rafael

[ruiu]

LGTM

ELF/Target.cpp

 }
 
 bool X86_64TargetInfo::needsCopyRelImpl(uint32_t Type) const {
   return Type == R_X86_64_32S || Type == R_X86_64_32 || Type == R_X86_64_PC32 ||
          Type == R_X86_64_64;
 }
 
 bool X86_64TargetInfo::refersToGotEntry(uint32_t Type) const {
-  return Type == R_X86_64_GOTPCREL;
+  return Type == R_X86_64_GOTPCREL || Type == R_X86_64_GOTPCRELX ||
+         Type == R_X86_64_REX_GOTPCRELX;
 }
 
 bool X86_64TargetInfo::needsGot(uint32_t Type, SymbolBody &S) const {
   if (Type == R_X86_64_TLSGD)
     return Target->canRelaxTls(Type, &S) && S.isPreemptible();
   if (Type == R_X86_64_GOTTPOFF)
     return !canRelaxTls(Type, &S);
   return refersToGotEntry(Type) || needsPlt<ELF64LE>(Type, S);
void X86_64TargetInfo::relocateOne(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type,
   case R_X86_64_64:
   case R_X86_64_DTPOFF64:
     write64le(Loc, SA);
     break;
   case R_X86_64_DTPOFF32:
     write32le(Loc, SA);
     break;
   case R_X86_64_GOTPCREL:
+  case R_X86_64_GOTPCRELX:
+  case R_X86_64_REX_GOTPCRELX:
   case R_X86_64_PC32:
   case R_X86_64_PLT32:
   case R_X86_64_TLSGD:
   case R_X86_64_TLSLD:
     write32le(Loc, SA - P);
     break;
   case R_X86_64_SIZE32:
     write32le(Loc, ZA);