Support for 64-bit PC-relative relocations for X86_64

[OlegPliss]

Summary

ELF files generated for X86_64 targets may contain 64-bit PC-relative relocations. For instance, an exception handler table entry contains the start of exception-throwing frame relative to the start of exception handler. As these two labels belong to different sections, their difference and so the relocation is 64-bit.

An attempt to parse such file, i.e. in DWARFContext::create, results in "failed to compute relocation" error.

The proposed simple and straightforward fix adds support for such relocations to RelocationResolver.cpp.

llvm/trunk/lib/Object/RelocationResolver.cpp

 
 static bool supportsX86_64(uint64_t Type) {
   switch (Type) {
   case ELF::R_X86_64_NONE:
   case ELF::R_X86_64_64:
   case ELF::R_X86_64_DTPOFF32:
   case ELF::R_X86_64_DTPOFF64:
   case ELF::R_X86_64_PC32:
+  case ELF::R_X86_64_PC64:
   case ELF::R_X86_64_32:
   case ELF::R_X86_64_32S:
     return true;
   default:
     return false;
   }
 }
 
 static uint64_t resolveX86_64(RelocationRef R, uint64_t S, uint64_t A) {
   switch (R.getType()) {
   case ELF::R_X86_64_NONE:
     return A;
   case ELF::R_X86_64_64:
   case ELF::R_X86_64_DTPOFF32:
   case ELF::R_X86_64_DTPOFF64:
     return S + getELFAddend(R);
   case ELF::R_X86_64_PC32:
+  case ELF::R_X86_64_PC64:
     return S + getELFAddend(R) - R.getOffset();
   case ELF::R_X86_64_32:
   case ELF::R_X86_64_32S:
     return (S + getELFAddend(R)) & 0xFFFFFFFF;
   default:
     llvm_unreachable("Invalid relocation type");
   }
 }