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Re: [PING][PATCH][REVISED] Fix PR middle-end/PR28690, modify swap_commutative_operands_p
On Tue, Jun 26, 2007 at 09:09:47PM -0500, Peter Bergner wrote:
> On Tue, 2007-06-26 at 16:27 -0700, Ian Lance Taylor wrote:
> > Peter's patch referenced above looks OK to me, and I'm inclined to
> > approve it. But some of these numbers do look troubling. Why do we
> > get such large swings in some of the benchmarks?
>
> Well, we mentioned one reason we saw in:
>
> http://gcc.gnu.org/ml/gcc-patches/2007-06/msg00808.html
>
> which was loop alignment related when x86_64's ".p2align 4,,7" isn't
> able to align the loop to what we asked for. In that case, it's just
> luck or bad luck on what alignment we end up with. In this case, it
> looks like HJ used his r125920 patch which should have helped some here,
> but given his change only allows skipping up to 10 bytes now, there
> might still be cases where we don't get the alignment we want.
That is not true:
http://gcc.gnu.org/ml/gcc-cvs/2007-06/msg00684.html
My patch adds ".p2align 3" after ".p2align 4,,X" for x86-64.
>
> I'm not sure about x86/x86_64 hardware, but on POWER, two identical
> loops that have the same alignment in the lowest nibble of their
> addresses can still have performance differences depending on where
> they show up in the cache line/cache line sector.
>
> HJ, can you send the binaries for 436.cactusADM, 454.calculix and
> 200.sixtrack to Pat and I and we'll try and track down exactly why
> they're slowing down when he gets back from vacation later this week.
Sure.
H.J.
- References:
- Re: [REVISED][PATCH/RFT] Fix PR middle-end/PR28690, modify swap_commutative_operands_p
- [PING][PATCH][REVISED] Fix PR middle-end/PR28690, modify swap_commutative_operands_p
- Re: [PING][PATCH][REVISED] Fix PR middle-end/PR28690, modify swap_commutative_operands_p
- Re: [PING][PATCH][REVISED] Fix PR middle-end/PR28690, modify swap_commutative_operands_p
- Re: [PING][PATCH][REVISED] Fix PR middle-end/PR28690, modify swap_commutative_operands_p
- Re: [PING][PATCH][REVISED] Fix PR middle-end/PR28690, modify swap_commutative_operands_p
- Re: [PING][PATCH][REVISED] Fix PR middle-end/PR28690, modify swap_commutative_operands_p
- Re: [PING][PATCH][REVISED] Fix PR middle-end/PR28690, modify swap_commutative_operands_p
- Re: [PING][PATCH][REVISED] Fix PR middle-end/PR28690, modify swap_commutative_operands_p
- Re: [PING][PATCH][REVISED] Fix PR middle-end/PR28690, modify swap_commutative_operands_p