[ELF][MIPS] - Explicitly list supported relocations for MIPS target.

[arichardson]

Summary

Do the same thing as x86 (D28564) also for MIPS.

I am not sure whether the R_MIPS_TLS_* cases are correct but it
matches the previous behaviour.

[grimar]

ELF/Target.cpp

2052

That 2 lines looks have a chance to return R_PC now:

if (&S == ElfSym<ELFT>::MipsGpDisp)
      return R_PC;

what is different from previous logic.
Is it correct ?

[atanasyan]

LGTM

ELF/Target.cpp

2034

We handle these relocations specifically in the MipsTargetInfo<ELFT>::relocateOne. We can introduce new expression type and adjust the relocation values in the getRelocTargetVA, but I think that is too much.

2052

In fact it is not possible to get R_MIPS_HIGHER and R_MIPS_HIGHEST against _gp_disp symbol in a real application. Probably the best choice is to show an error if any relocations except R_MIPS_HI16/LO16 has _gp_disp as a target. But for now the code above is okay.

[ruiu]

LGTM

ELF/Target.cpp

2034

Then please remove this FIXME.

2051–2052

Sort lines.

[grimar]

Looks it was forgotten and not committed.

[atanasyan]

Superseded by commit rL313882.

ELF/Target.cpp

 
 template <class ELFT>
 RelExpr MipsTargetInfo<ELFT>::getRelExpr(uint32_t Type,
                                          const SymbolBody &S) const {
   // See comment in the calculateMipsRelChain.
   if (ELFT::Is64Bits || Config->MipsN32Abi)
     Type &= 0xff;
   switch (Type) {
-  default:
+  case R_MIPS_32:
+  case R_MIPS_64:
+  case R_MIPS_SUB:
+  // FIXME: are all these really R_ABS and not R_TLS*?
+  case R_MIPS_TLS_DTPREL64:
+  case R_MIPS_TLS_DTPREL32:
+  case R_MIPS_TLS_DTPREL_HI16:
+  case R_MIPS_TLS_DTPREL_LO16:
+  case R_MIPS_TLS_TPREL64:
+  case R_MIPS_TLS_TPREL32:
+  case R_MIPS_TLS_TPREL_HI16:
+  case R_MIPS_TLS_TPREL_LO16:
     return R_ABS;
   case R_MIPS_JALR:
     return R_HINT;
   case R_MIPS_GPREL16:
   case R_MIPS_GPREL32:
     return R_MIPS_GOTREL;
   case R_MIPS_26:
     return R_PLT;
+  case R_MIPS_HIGHEST:
+  case R_MIPS_HIGHER:
   case R_MIPS_HI16:
   case R_MIPS_LO16:
   case R_MIPS_GOT_OFST:
     // R_MIPS_HI16/R_MIPS_LO16 relocations against _gp_disp calculate
     // offset between start of function and 'gp' value which by default
     // equal to the start of .got section. In that case we consider these
     // relocations as relative.
     if (&S == ElfSym<ELFT>::MipsGpDisp)
RelExpr MipsTargetInfo<ELFT>::getRelExpr(uint32_t Type,
   case R_MIPS_GOT_LO16:
     return R_MIPS_GOT_OFF32;
   case R_MIPS_GOT_PAGE:
     return R_MIPS_GOT_LOCAL_PAGE;
   case R_MIPS_TLS_GD:
     return R_MIPS_TLSGD;
   case R_MIPS_TLS_LDM:
     return R_MIPS_TLSLD;
+  default:
+    error("do not know how to handle relocation '" + toString(Type) + "' (" +
+          Twine(Type) + ")");
+    return R_HINT;
   }
 }
 
 template <class ELFT> bool MipsTargetInfo<ELFT>::isPicRel(uint32_t Type) const {
   return Type == R_MIPS_32 || Type == R_MIPS_64;
 }
 
 template <class ELFT>
case R_MIPS_PC21_S2:
     break;
   case R_MIPS_PC26_S2:
     applyMipsPcReloc<E, 26, 2>(Loc, Type, Val);
     break;
   case R_MIPS_PC32:
     applyMipsPcReloc<E, 32, 0>(Loc, Type, Val);
     break;
   default:
-    error(getErrorLocation(Loc) + "unrecognized reloc " + Twine(Type));
+    llvm_unreachable("unexpected relocation");
   }
 }
 
 template <class ELFT>
 bool MipsTargetInfo<ELFT>::usesOnlyLowPageBits(uint32_t Type) const {
   return Type == R_MIPS_LO16 || Type == R_MIPS_GOT_OFST;
 }
 }
 }