[PATCH] D74507: [llvm-objdump] Print method name from debug info in disassembly output.

[Jordan Rupprecht via Phabricator via llvm-commits]

rupprecht added a comment.

Sure, here's an example you can play around with:

  $ echo 'extern "C" int foo() { return 5; }; namespace xyz { int bar() { return 10; } }' > /tmp/src.cc; clang++ -g -c /tmp/src.cc -o /tmp/obj.o
  $ objdump -ldC /tmp/obj.o  # GNU objdump
  ...
  Disassembly of section .text:
  
  0000000000000000 <foo>:
  foo():
  /tmp/src.cc:1
     0:   55                      push   %rbp
     1:   48 89 e5                mov    %rsp,%rbp
     4:   b8 05 00 00 00          mov    $0x5,%eax
     9:   5d                      pop    %rbp
     a:   c3                      retq   
     b:   0f 1f 44 00 00          nopl   0x0(%rax,%rax,1)
  
  0000000000000010 <xyz::bar()>:
  _ZN3xyz3barEv():  # <-- Note, see https://sourceware.org/ml/binutils/2020-02/msg00369.html to demangle this too
  /tmp/src.cc:1
    10:   55                      push   %rbp
    11:   48 89 e5                mov    %rsp,%rbp
    14:   b8 0a 00 00 00          mov    $0xa,%eax
    19:   5d                      pop    %rbp
    1a:   c3                      retq   
  
  $ llvm-objdump -ldC /tmp/obj.o  # llvm-objdump, w/o this patch
  ...
  0000000000000000 foo:
  ; /tmp/src.cc:1
         0: 55                            pushq   %rbp
         1: 48 89 e5                      movq    %rsp, %rbp
         4: b8 05 00 00 00                movl    $5, %eax
         9: 5d                            popq    %rbp
         a: c3                            retq
         b: 0f 1f 44 00 00                nopl    (%rax,%rax)
  
  0000000000000010 xyz::bar():
        10: 55                            pushq   %rbp
        11: 48 89 e5                      movq    %rsp, %rbp
        14: b8 0a 00 00 00                movl    $10, %eax
        19: 5d                            popq    %rbp
        1a: c3                            retq
  
  $ llvm-objdump -ldC /tmp/obj.o  # llvm-objdump, w/ this patch
  ...
  0000000000000000 foo:
  ; foo():  # <-- this is new
  ; /tmp/src.cc:1
         0: 55                            pushq   %rbp
         1: 48 89 e5                      movq    %rsp, %rbp
         4: b8 05 00 00 00                movl    $5, %eax
         9: 5d                            popq    %rbp
         a: c3                            retq
  ; /tmp/src.cc:1 # <-- just noticed this unexpected diff, I'll see what's going on here....
         b: 0f 1f 44 00 00                nopl    (%rax,%rax)
  
  0000000000000010 xyz::bar():
  ; _ZN3xyz3barEv(): # <-- this is new
  ; /tmp/src.cc:1 # <-- this is new and correct (although wasn't the intention of this patch to fix)
        10: 55                            pushq   %rbp
        11: 48 89 e5                      movq    %rsp, %rbp
        14: b8 0a 00 00 00                movl    $10, %eax
        19: 5d                            popq    %rbp
        1a: c3                            retq

http://llvm.org/PR41341 also has some examples. It seems superfluous with the trivial examples, but helps in situations where the object file has debugging information but no (or limited) symbols.

Note this patch doesn't address the syntactic difference of the leading `;` delimiter, which is still a difference between llvm-objdump and GNU objdump.


Repository:
  rG LLVM Github Monorepo

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