[llvm-objdump] Correctly distinguish between the MachO upper/lower16 relocations

[mstorsjo]

Summary

All other code in MachODump.cpp uses the same comparison, ((r_length & 0x1) == 1), for distinguishing between the two, while the code in llvm-objdump.cpp seemed to be incorrect.

[lhames]

LGTM.

I believe thumb mode uses 3/2 in the length field, rather than 1/0. Would you be interested in adding support and a test case for that too?

[lhames]

Oops - I didn't look closely enough: I thought you were just comparing against 1, but you're actually masking with 0x1 first, so this should work as-is for both ARM and Thumb encodings.

llvm/trunk/test/tools/llvm-objdump/ARM/macho-reloc-half.test

+RUN: llvm-objdump -r %p/Inputs/reloc-half.obj.macho-arm | FileCheck %s
+
+CHECK-DAG: 00000004 ARM_RELOC_HALF :upper16:(_stringbuf)
+CHECK-DAG: 00000000 ARM_RELOC_HALF :lower16:(_stringbuf)

llvm/trunk/tools/llvm-objdump/llvm-objdump.cpp

if (Arch == Triple::x86 || Arch == Triple::ppc) {
         printRelocationTargetName(Obj, RE, fmt);
       }
     } else { // ARM-specific relocations
       switch (Type) {
       case MachO::ARM_RELOC_HALF:
       case MachO::ARM_RELOC_HALF_SECTDIFF: {
         // Half relocations steal a bit from the length field to encode
         // whether this is an upper16 or a lower16 relocation.
-        bool isUpper = Obj->getAnyRelocationLength(RE) >> 1;
+        bool isUpper = (Obj->getAnyRelocationLength(RE) & 0x1) == 1;
 
         if (isUpper)
           fmt << ":upper16:(";
         else
           fmt << ":lower16:(";
         printRelocationTargetName(Obj, RE, fmt);
 
         DataRefImpl RelNext = Rel;