Add R_HEX_GOT_16_X support

[sidneym]

Summary

Wow! Just 280 lines of target-specific code and lld will link both the linux kernel and musl libc.so for hexagon.

[ruiu]

LGTM

Congratulations! I'm happy to see this concrete example that lld is *very* hackable and extremely easy to extend. :) We've been emphasizing simplicity, and it surely pays off.

[ruiu]

Sid,

Is this your final patch to support Hexagon, or do you have any other plans? I'm just wondering.

[sidneym]

No this isn't, I'd like to add TLS support. I'm also sure some additional relocations will be required (beyond the TLS ones).

lld/trunk/ELF/Arch/Hexagon.cpp

RelExpr Hexagon::getRelExpr(RelType Type, const Symbol &S,
   case R_HEX_32_PCREL:
     return R_PC;
   case R_HEX_B22_PCREL:
   case R_HEX_PLT_B22_PCREL:
   case R_HEX_B22_PCREL_X:
   case R_HEX_B32_PCREL_X:
     return R_PLT_PC;
   case R_HEX_GOT_11_X:
+  case R_HEX_GOT_16_X:
   case R_HEX_GOT_32_6_X:
     return R_HEXAGON_GOT;
   default:
     return R_ABS;
   }
 }
 
 static uint32_t findMaskR6(uint32_t Insn) {
case R_HEX_10_X:
     break;
   case R_HEX_11_X:
   case R_HEX_GOT_11_X:
     or32le(Loc, applyMask(findMaskR11(read32le(Loc)), Val & 0x3f));
     break;
   case R_HEX_12_X:
     or32le(Loc, applyMask(0x000007e0, Val));
     break;
-  case R_HEX_16_X: // This reloc only has 6 effective bits.
+  case R_HEX_16_X: // These relocs only have 6 effective bits.
+  case R_HEX_GOT_16_X:
     or32le(Loc, applyMask(findMaskR16(read32le(Loc)), Val & 0x3f));
     break;
   case R_HEX_32:
   case R_HEX_32_PCREL:
     or32le(Loc, Val);
     break;
   case R_HEX_32_6_X:
   case R_HEX_GOT_32_6_X:

lld/trunk/test/ELF/hexagon-shared.s

 # R_HEX_PLT_B22_PCREL
 call bar@PLT
 
 # R_HEX_GOT_11_X and R_HEX_GOT_32_6_X
 r2=add(pc,##_GLOBAL_OFFSET_TABLE_@PCREL)
 r0 = memw (r2+##bar@GOT)
 jumpr r0
 
+# R_HEX_GOT_16_X
+r0 = add(r1,##bar@GOT)
+
 # PLT: { immext(#65472
 # PLT: r28 = add(pc,##65488) }
 # PLT: { r14 -= add(r28,#16)
 # PLT: r15 = memw(r28+#8)
 # PLT: r28 = memw(r28+#4) }
 # PLT: { r14 = asr(r14,#2)
 # PLT: jumpr r28 }
 # PLT: { trap0(#219) }
 # PLT: immext(#65472)
 # PLT: r14 = add(pc,##65472) }
 # PLT: r28 = memw(r14+#0) }
 # PLT: jumpr r28 }
 
 # TEXT:  10000: 00 00 02 00 00020000
 # TEXT: {   call 0x10050 }
+# TEXT: r0 = add(r1,##65664) }
 
 # GOT: .got:
 # GOT: 30080: 00 00 00 00 00000000 <unknown>