ARM fix encoding fixup resolution for ldrd and friends.

The 8-bit payload is not contiguous in the opcode. Move the upper nibble
over 4 bits into the correct place.

rdar://11158641

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153780 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp

@@ -469,7 +469,9 @@ static unsigned adjustFixupValue(unsigned Kind, uint64_t Value) {
       Value = -Value;
       isAdd = false;
     }
+    // The value has the low 4 bits encoded in [3:0] and the high 4 in [11:8].
     assert ((Value < 256) && "Out of range pc-relative fixup value!");
+    Value = (Value & 0xf) | ((Value & 0xf0) << 4);
     return Value | (isAdd << 23);
   }
   case ARM::fixup_arm_pcrel_10: