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Re: [PATCH i386]: Enable push/pop in pro/epilogue for modern CPUs
- From: Uros Bizjak <ubizjak at gmail dot com>
- To: gcc-patches at gcc dot gnu dot org
- Cc: Xinliang David Li <davidxl at google dot com>
- Date: Sun, 9 Dec 2012 14:50:10 +0100
- Subject: Re: [PATCH i386]: Enable push/pop in pro/epilogue for modern CPUs
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.