Em Thu, Feb 11, 2021 at 01:37:55PM +0100, Martin Liška escreveu:
> Considering the following testcase:
>
> int
> foo(int a, int b)
> {
> for (unsigned i = 0; i < 1000000000; i++)
> a += b;
> return a;
> }
>
> int main()
> {
> foo (3, 4);
> return 0;
> }
>
> perf annotate displays:
> 86.52 │40055e: → ja 40056c <foo(int, int)+0x26>
> 13.37 │400560: mov -0x18(%rbp),%eax
> │400563: add %eax,-0x14(%rbp)
> │400566: addl $0x1,-0x4(%rbp)
> 0.11 │40056a: → jmp 400557 <foo(int, int)+0x11>
> │40056c: mov -0x14(%rbp),%eax
> │40056f: pop %rbp
>
> and the 'ja 40056c' does not link to the location in the function.
> It's caused by fact that comma is wrongly parsed, it's part
> of function signature.
>
> With my patch I see:
>
> 86.52 │ ┌──ja 26
> 13.37 │ │ mov -0x18(%rbp),%eax
> │ │ add %eax,-0x14(%rbp)
> │ │ addl $0x1,-0x4(%rbp)
> 0.11 │ │↑ jmp 11
> │26:└─→mov -0x14(%rbp),%eax
>
> and 'o' output prints:
> 86.52 │4005┌── ↓ ja 40056c <foo(int, int)+0x26>
> 13.37 │4005│0: mov -0x18(%rbp),%eax
> │4005│3: add %eax,-0x14(%rbp)
> │4005│6: addl $0x1,-0x4(%rbp)
> 0.11 │4005│a: ↑ jmp 400557 <foo(int, int)+0x11>
> │4005└─→ mov -0x14(%rbp),%eax
So, before your patch, this is what I am seeing:
[acme@five c]$ cat cpp_args_annotate.c
int
foo(int a, int b)
{
for (unsigned i = 0; i < 1000000000; i++)
a += b;
return a;
}
int main()
{
foo (3, 4);
return 0;
}
[acme@five c]$ gcc --version |& head -1
gcc (GCC) 10.2.1 20201125 (Red Hat 10.2.1-9)
[acme@five c]$ gcc -g cpp_args_annotate.c -o cpp_args_annotate
[acme@five c]$ perf record ./cpp_args_annotate
[ perf record: Woken up 2 times to write data ]
[ perf record: Captured and wrote 0.275 MB perf.data (7188 samples) ]
[acme@five c]$ perf annotate --stdio2 foo
Samples: 7K of event 'cycles:u', 4000 Hz, Event count (approx.): 7468429289,
[percent: local period]
foo() /home/acme/c/cpp_args_annotate
Percent
0000000000401106 <foo>:
foo():
int
foo(int a, int b)
{
push %rbp
mov %rsp,%rbp
mov %edi,-0x14(%rbp)
mov %esi,-0x18(%rbp)
for (unsigned i = 0; i < 1000000000; i++)
movl $0x0,-0x4(%rbp)
↓ jmp 1d
a += b;
13.45 13: mov -0x18(%rbp),%eax
add %eax,-0x14(%rbp)
for (unsigned i = 0; i < 1000000000; i++)
addl $0x1,-0x4(%rbp)
0.09 1d: cmpl $0x3b9ac9ff,-0x4(%rbp)
86.46 ↑ jbe 13
return a;
mov -0x14(%rbp),%eax
}
pop %rbp
← retq
[acme@five c]$
Ok, now I see:
[acme@five c]$ g++ -g cpp_args_annotate.c -o cpp_args_annotate
[acme@five c]$ perf record ./cpp_args_annotate
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.268 MB perf.data (6976 samples) ]
[acme@five c]$ perf annotate --stdio2 foo
Samples: 6K of event 'cycles:u', 4000 Hz, Event count (approx.): 7380681761,
[percent: local period]
foo() /home/acme/c/cpp_args_annotate
Percent
0000000000401106 <foo(int, int)>:
foo(int, int):
int
foo(int a, int b)
{
push %rbp
mov %rsp,%rbp
mov %edi,-0x14(%rbp)
mov %esi,-0x18(%rbp)
for (unsigned i = 0; i < 1000000000; i++)
movl $0x0,-0x4(%rbp)
cmpl $0x3b9ac9ff,-0x4(%rbp)
86.53 → ja 40112c <foo(int, int)+0x26>
a += b;
13.32 mov -0x18(%rbp),%eax
0.00 add %eax,-0x14(%rbp)
for (unsigned i = 0; i < 1000000000; i++)
addl $0x1,-0x4(%rbp)
0.15 → jmp 401117 <foo(int, int)+0x11>
return a;
mov -0x14(%rbp),%eax
}
pop %rbp
← retq
[acme@five c]$
Ok, continuing the test...
- Arnaldo
