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Re: [PING] [PATCH] faster string operations for bulldozer (take 2)
- From: Roland McGrath <roland at hack dot frob dot com>
- To: OndÅej BÃlka <neleai at seznam dot cz>
- Cc: Carlos O'Donell <carlos at systemhalted dot org>, libc-alpha at sourceware dot org
- Date: Fri, 26 Apr 2013 23:50:02 -0700 (PDT)
- Subject: Re: [PING] [PATCH] faster string operations for bulldozer (take 2)
- References: <20120926171541 dot GA12300 at domone dot kolej dot mff dot cuni dot cz> <20120926172758 dot 56BEC2C097 at topped-with-meat dot com> <20120926184013 dot GA13454 at domone dot kolej dot mff dot cuni dot cz> <20120926194423 dot 15F9B2C061 at topped-with-meat dot com> <20120926211433 dot GA17771 at domone dot kolej dot mff dot cuni dot cz> <CAE2sS1i2nfrn58PNwtOXYx9qt=bWX_C4_fJN=CnGuefBTvN-Bw at mail dot gmail dot com> <20120930103730 dot GA5682 at domone dot kolej dot mff dot cuni dot cz> <20130426165614 dot GA16694 at domone dot kolej dot mff dot cuni dot cz> <20130426192321 dot 720E02C061 at topped-with-meat dot com> <20130427011233 dot GA19026 at domone dot kolej dot mff dot cuni dot cz>
> On bulldozer unaligned loads have small penalty. You could read about
> buldozer improvements or test it by simple benchmark.
>
> And what evidence that avx on intel processors is always
> correlated with efficiency of unaligned loads?
I don't understand what you're saying or how it constitutes a sensical
answer to my question. If a particular model or family of chip models has
efficient unaligned loads, then setting the flag should be contingent on
that model/family detection, not on AVX support. Your change makes it
contingent only on AVX support, with no explanation of why that should be
taken as an indicator of efficient unaligned loads.