PATCH: Optimize IA64 brl to br

H. J. Lu hjl@lucon.org
Thu Jan 29 17:07:00 GMT 2004


On Wed, Jan 28, 2004 at 04:13:39PM -0800, Zack Weinberg wrote:
> "H. J. Lu" <hjl@lucon.org> writes:
> 
> > The IA64 compiler may generate brl. But it may be replaced by br
> > during the relax finalize pass. This patch implements it.
> 
> Is this replacement actually an improvement?  It doesn't shrink the
> code, or execute anything in the now-freed-up slot, so the only way
> it could be is if br is faster than brl, and this I find unlikely.

I was told that br is faster than brl. It has something to do with
branch prediction on hardware.


H.J.



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