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Re: Proposed doc update for Explicit Reg Vars 3/3


On 10/20/2015 11:11 AM, Segher Boessenkool wrote:
On Tue, Oct 20, 2015 at 10:22:53AM -0600, Jeff Law wrote:
bz21182 has a testcase that's still helped by local register variables.

I tried it out, and it now is much worse *with* the reg vars than
without (and -O2 vs. -O3 makes no difference at all).  It doesn't look
to have used the pre-determined allocation at all.  The difference at
expand time is huge already; maybe some things weren't optimised at
tree level with the register vars?  It's a bit big to really look into ;-)
We must be evaluating different things. I review the state of that bug each release. While the amount of stack slot shuffling has improved over time it still looked better with the register variables during the gcc-5 release cycle.

jeff


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