realloc stack use under O0 for x86_64

[D'Alessandro, Luke K]

> On Mar 25, 2015, at 8:47 PM, Matthew Hall <mhall at mhcomputing.net> wrote:
> 
> On Mar 25, 2015, at 11:48 AM, D'Alessandro, Luke K <ldalessa at indiana.edu> wrote:
>> When we compile jemalloc for debugging purposes, we see realloc using a 
>> large amount of stack space:
>> 
>> ```asm
>> 0000000000070e48 <realloc>:
>>  70e48:       55                      push   %rbp
>>  70e49:       48 89 e5                mov    %rsp,%rbp
>>  70e4c:       53                      push   %rbx
>>  70e4d:       48 81 ec 68 62 00 00    sub    $0x6268,%rsp
>> ```
> 
> I think perhaps we can do a little better on narrowing this down especially 
> given you said that it occurs in -O0 mode.
> 
> If you dump this code using objdump -C -d -l, it will try to find the file 
> name and line number from the debug symbols, and annotate the assembly with 
> these.
> 
> Can you give it a try and search for the 0x6268 and scroll up from there to 
> find the nearest lines of code to the issue?

Sure, hope this is what you’re after:

0000000000070e48 <realloc>:
realloc():
/u/ldalessa/jemalloc/src/jemalloc.c:1738
   70e48:       55                      push   %rbp
   70e49:       48 89 e5                mov    %rsp,%rbp
   70e4c:       53                      push   %rbx
   70e4d:       48 81 ec 68 62 00 00    sub    $0x6268,%rsp
   70e54:       48 89 bd a8 9d ff ff    mov    %rdi,-0x6258(%rbp)
   70e5b:       48 89 b5 a0 9d ff ff    mov    %rsi,-0x6260(%rbp)
/u/ldalessa/jemalloc/src/jemalloc.c:1740
   70e62:       48 c7 85 60 9e ff ff    movq   $0x0,-0x61a0(%rbp)
   70e69:       00 00 00 00 
/u/ldalessa/jemalloc/src/jemalloc.c:1741
   70e6d:       48 c7 85 58 9e ff ff    movq   $0x0,-0x61a8(%rbp)
   70e74:       00 00 00 00 
/u/ldalessa/jemalloc/src/jemalloc.c:1742
   70e78:       48 c7 45 e0 00 00 00    movq   $0x0,-0x20(%rbp)
   70e7f:       00 
/u/ldalessa/jemalloc/src/jemalloc.c:1743
   70e80:       48 c7 45 d8 00 00 00    movq   $0x0,-0x28(%rbp)
   70e87:       00 
/u/ldalessa/jemalloc/src/jemalloc.c:1745
   70e88:       48 83 bd a0 9d ff ff    cmpq   $0x0,-0x6260(%rbp)
   70e8f:       00 
   70e90:       0f 94 c0                sete   %al
   70e93:       0f b6 c0                movzbl %al,%eax
   70e96:       48 85 c0                test   %rax,%rax
   70e99:       0f 84 74 04 00 00       je     71313 <realloc+0x4cb>
/u/ldalessa/jemalloc/src/jemalloc.c:1746
   70e9f:       48 83 bd a8 9d ff ff    cmpq   $0x0,-0x6258(%rbp)
   70ea6:       00 
   70ea7:       0f 84 5b 04 00 00       je     71308 <realloc+0x4c0>
je_tsd_get():

> Apologies if you already tried this and it didn't work. It helped me in the 
> past.


No, I’m not an expert objdump user. Normally just -S things or read LLVM IR, but this file is so big that I didn’t want to do that if possible.

Luke