Re: Re-tune x86 uaccess code for PREEMPT_VOLUNTARY

[H. Peter Anvin]

On 08/10/2013 11:51 AM, Linus Torvalds wrote:
> Note that you still want the *test* to be done in C code, because together
> with "unlikely()" you'd likely do pretty close to optimal code
> generation, and hiding the decrement and test and conditional jump in
> asm you wouldn't get the proper instruction scheduling and branch
> following that gcc does.

How much instruction scheduling can gcc actually do given that there is
a barrier involved?  I guess some on the RISC architectures which need
load/subtract/store...

	-hpa


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