On 08/09/2011 10:25 AM, Olivier Maury wrote:
Hi all,
I was wondering, is the following assembly code correct:
c94: e8 fc ff ff ff call c95
<load_param_def_given+0x1d1>
c99: 84 c0 test %al,%al
c9b: dd 45 d0 fldl -0x30(%ebp)
c9e: dd 45 d8 fldl -0x28(%ebp)
ca1: da c9 fcmove %st(1),%st
ca3: dd d9 fstp %st(1)
ca5: dd 5d d0 fstpl -0x30(%ebp)
ca8: 89 f8 mov %edi,%eax
This code is some optimized assembly code extracted from the object
file using objdump. My concern here is that I have a test instruction
without the corresponding jump !
That piece of assembly comes from a code that look like:
if (my_function(param1, &out_param))
value = out_param;
with :
out_param a double value that is not assigned with a default value
and
char my_function(long param1, double *out)
{
char ret = 0;
... do some stuff ...
if (some_property)
{
... do some stuff ...
*out = a_value_computed;
ret = 1;
}
....
return ret;
}
And taking that optimized code in a debugger it crash with a FPE from
time to time because even if the my_function returns 0 it seems to do
the assignement (value = out_param) with an unitialized out_param value !
What do you think ? Am I doing something wrong or is it a gcc bug ?
Regards
Olivier
Isn't fcmove a conditional floating move?
--jeff
