* -mno-bmi doesn't work in GCC4.8.2
@ 2014-08-10 3:47 hanhwi
2014-08-10 15:02 ` Ryan Mansfield
0 siblings, 1 reply; 2+ messages in thread
From: hanhwi @ 2014-08-10 3:47 UTC (permalink / raw)
To: gcc-help
Hi, all,
I'm using GCC 4.8.2 on x86-64 machine. The compiler emits tzcnt instruction
unlike previous gcc. I want to prevent using tzcnt instruction. As I know,
tzcnt instruction is BMI extension. To disable the feature, I set -mno-bmi
but it didn't work.
Is there any way to disable tzcnt instruction?
Thanks,
Hanhwi
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* Re: -mno-bmi doesn't work in GCC4.8.2
2014-08-10 3:47 -mno-bmi doesn't work in GCC4.8.2 hanhwi
@ 2014-08-10 15:02 ` Ryan Mansfield
0 siblings, 0 replies; 2+ messages in thread
From: Ryan Mansfield @ 2014-08-10 15:02 UTC (permalink / raw)
To: gcc-help
On 14-08-09 11:46 PM, hanhwi wrote:
> Hi, all,
>
> I'm using GCC 4.8.2 on x86-64 machine. The compiler emits tzcnt instruction
> unlike previous gcc. I want to prevent using tzcnt instruction. As I know,
> tzcnt instruction is BMI extension. To disable the feature, I set -mno-bmi
> but it didn't work.
I believe starting with 4.8 gcc unconditionally emits tzcnt, as non-bmi
targets will handle it as rep;bsf, and bmi targets will treat it as a tzcnt.
Regards,
Ryan Mansfield
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