[llvm-objdump,ARM] Fix .byte directives dumping the wrong byte.

[simon_tatham]

Summary

The clause in dumpARMELFData that dumps a single byte as a .byte
directive was printing the operand of that directive as Bytes[0],
not Bytes[Index]. In particular, this led to the dumpBytes output
to its left not matching it!

[MaskRay]

Thanks for catching the ARM bug. In the test, 0 is a very common value and the test may still pass with other types of wrong-index bugs. Can you improve the test a bit?

[simon_tatham]

Good point, thanks. Updated the test to contain a more distinctive value in the final byte of the data section.

[DavidSpickett]

LGTM

llvm/test/tools/llvm-objdump/ELF/AArch64/elf-aarch64-mapping-symbols.test

 # RUN: llvm-mc -filetype=obj -triple=aarch64-unknown-freebsd %s -o %t
 # RUN: llvm-objdump -d %t | FileCheck %s
 
 .section .mysection,"ax",@progbits
 .globl _start
 _start:
   adr x1,msg
 msg:  .asciz  "Hello, world\n"
 msgend:
 
 .section .myothersection,"ax",@progbits
   adrp x1,mystr
 mystr:
-  .asciz "blah"
+  .ascii "blah"
   .size mystr, 4
+  .byte 0x9a
 
 # CHECK: Disassembly of section .mysection:
 # CHECK: <_start>:
 # CHECK:        0:       21 00 00 10     adr     x1, #4
 # CHECK: <msg>:
 # CHECK:        4:       48 65 6c 6c     .word
 # CHECK:        8:       6f 2c 20 77     .word
 # CHECK:        c:       6f 72 6c 64     .word
 # CHECK:       10:       0a 00           .short  0x000a
 # CHECK: Disassembly of section .myothersection:
 # CHECK: <$x.2>:
 # CHECK:        0:       01 00 00 90     adrp    x1, 0x0
 # CHECK: <mystr>:
 # CHECK:        4:       62 6c 61 68     .word
-# CHECK:        8:       00              .byte   0x01
+# CHECK:        8:       9a              .byte   0x9a

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

static uint64_t dumpARMELFData(uint64_t SectionAddr, uint64_t Index,
   if (Index + 2 <= End) {
     dumpBytes(Bytes.slice(Index, 2), OS);
     OS << "\t\t.short\t"
            << format_hex(support::endian::read16(Bytes.data() + Index, Endian),
                          6);
     return 2;
   }
   dumpBytes(Bytes.slice(Index, 1), OS);
-  OS << "\t\t.byte\t" << format_hex(Bytes[0], 4);
+  OS << "\t\t.byte\t" << format_hex(Bytes[Index], 4);
   return 1;
 }
 
 static void dumpELFData(uint64_t SectionAddr, uint64_t Index, uint64_t End,
                         ArrayRef<uint8_t> Bytes) {
   // print out data up to 8 bytes at a time in hex and ascii
   uint8_t AsciiData[9] = {'\0'};
   uint8_t Byte;