[PATCH i386]: Enable push/pop in pro/epilogue for modern CPUs

Дмитрий Дьяченко dimhen@gmail.com
Sun Dec 9 17:09:00 GMT 2012



2012/12/9 Uros Bizjak <ubizjak@gmail.com>:
> Hello!
>> I noticed in prologue/epilogue, GCC prefers to use MOVs followed by a
>> SP adjustment instead of a sequence of pushes/pops. The preference to
>> the MOVs are good for old CPU micro-architectures (before pentium-4,
>> K10), because it breaks the data dependency.  In modern
>> micro-architecture, push/pop is implemented using a mechanism called
>> stack engine. The data dependency is removed by the hardware, and
>> push/pop becomes very cheap (1 uOp, 1 cycle latency), and they are
>> smaller. There is no longer the need to avoid using them.   This is
>> also what ICC does.
>> 2012-12-08  Xinliang David Li  <davidxl@google.com>
>>            * config/i386/i386.c: Eanble push/pop in pro/epilogue for moderen CPUs.
> s/moderen/modern
> OK for mainline SVN.
> Thanks,
> Uros.

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