Dear sir,
gcc-4.4.0 mis-schedules the instructions. It causes the wrong return
values in r0 and r1.
But, gcc-4.5.0 does the right thing to schedule the instructions. How
do I fix this in
gcc-4.4.0? Thank you.
Cheers
Mingfeng
Source code:
typedef unsigned long long float64;
float64 syst_float64_div( float64 a, float64 b )
{
float64 z;
*( (double *) &z ) = *( (double *) &a ) / *( (double *) &b );
return z;
}
Compile options:
-O2 -mfloat-abi=softfp -mfpu=vfp -S
GCC-4.4.0 outputs:
syst_float64_div:
@ args = 0, pretend = 0, frame = 8
@ frame_needed = 0, uses_anonymous_args = 0
@ link register save eliminated.
fmdrr d5, r0, r1
fmdrr d6, r2, r3
sub sp, sp, #8
ldr r0, [sp, #0]
fdivd d7, d5, d6
ldr r1, [sp, #4]
fstd d7, [sp, #0]
add sp, sp, #8
bx lr
.size syst_float64_div, .-syst_float64_div
GCC-4.5.0 outputs:
syst_float64_div:
@ args = 0, pretend = 0, frame = 24
@ frame_needed = 0, uses_anonymous_args = 0
@ link register save eliminated.
sub sp, sp, #24
strd r0, [sp, #8]
strd r2, [sp]
fldd d7, [sp, #0]
fldd d6, [sp, #8]
fdivd d7, d6, d7
fstd d7, [sp, #16]
ldr r0, [sp, #16]
ldr r1, [sp, #20]
add sp, sp, #24
bx lr
.size syst_float64_div, .-syst_float64_div
