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Re: Comments in assember output

by Tony Wetmore :: Rate this Message:

Artur,

I just tried playing around with this, and it appears the the "-S" flag
is interfering. Perhaps by stopping the compilation process in that
way, it prevents the generation of the "listing file".

I tried compiling your example function as follows:

gcc -c -g -O3 -Wa,-adhls=func.list func.c

And got the following output (in func.list):

1 .file "func.c"
4 .text
5 Ltext0:
28 .p2align 4,,15
32 .globl _func
34 _func:
1:func.c **** float func( float a, float b )
2:func.c **** {
36 LM1:
37 0000 55 pushl %ebp
38 0001 89E5 movl %esp, %ebp
40 LM2:
41 0003 D9450C flds 12(%ebp)
3:func.c **** return a * b;
43 LM3:
44 0006 D84D08 fmuls 8(%ebp)
4:func.c **** }
46 LM4:
47 0009 5D popl %ebp
48 000a C3 ret
50 Lscope0:
52 .text
54 000b 90909090 Letext:
54 90

This appears to be the sort of output you are looking for, right?

--
Tony Wetmore
Solipsys Corporation (http://www.solipsys.com)
mailto:tony.wetmore@...

Artur Krzysztof Szostak wrote:

>> I don't think there is any simple way to do this without using the -g
>> option.
>>
>> Note that the -g option does not affect code generation in any way.
>> You can use -O3 with or without -g, and you will get the same code.
>>
>
> Will the -g -O3 option truly give me code that executed at the same speed
> as -O3? I was not aware of that. In that case -g is fine. But even with -g I
> am not getting the result I want. I guess it is time for a specific example:
> Lets say I have the fillowing code in test.cxx
>
> float func(float a, float b)
> {
> return a * b;
> }
>
> and try to generate the assembly with
>
> g++ -g -O3 -Wa,-addhls test.cxx -S
>
> I would get the following (This output is truncated, I left out all the debug
> symbols at the end):
>
> # ... bla bla bla...
> .LFB2:
> .file 1 "test.cxx"
> .loc 1 3 0
> .LVL0:
> pushl %ebp
> .LCFI0:
> movl %esp, %ebp
> .LCFI1:
> .loc 1 3 0
> flds 12(%ebp)
> .LBB2:
> .loc 1 4 0
> fmuls 8(%ebp)
> .LBE2:
> .loc 1 5 0
> leave
> ret
> .LFE2:
> .size _Z4funcff, .-_Z4funcff
> # ... etc ...
>
>
> And I dont see any comments containing my c++ source lines. I would have
> expected something like:
>
> # ... bla bla bla...
> .LFB2:
> .file 1 "test.cxx"
> .loc 1 3 0
> # float func(float a, float b)
> # {
> .LVL0:
> pushl %ebp
> # return a * b;
> .LCFI0:
> movl %esp, %ebp
> .LCFI1:
> .loc 1 3 0
> flds 12(%ebp)
> .LBB2:
> .loc 1 4 0
> fmuls 8(%ebp)
> .LBE2:
> .loc 1 5 0
> leave
> ret
> # }
> .LFE2:
> .size _Z4funcff, .-_Z4funcff
> # ... etc ...
>
>
> Any ideas how to get his kind of output?
>

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