| commit | 7ee8467b276fbe442df8c84c3d13a99e80519c24 | [log] [tgz] |
|---|---|---|
| author | Josh Bleecher Snyder <josharian@gmail.com> | Sat Apr 04 19:22:28 2020 -0700 |
| committer | Josh Bleecher Snyder <josharian@gmail.com> | Tue Apr 07 18:19:55 2020 +0000 |
| tree | 9c85ac85cbcf84fd378abc93c694c00cb258e16b | |
| parent | 64f19d70805a6da347a55dab5ab4f4c57ddb3278 [diff] |
cmd/compile: use MOVBQZX for OpAMD64LoweredHasCPUFeature In the commit message of CL 212360, I wrote: > This new intrinsic ... generates MOVB+TESTB+NE. > (It is possible that MOVBQZX+TESTQ+NE would be better.) I should have tested. MOVBQZX+TESTQ+NE does in fact appear to be better. For the benchmark in #36196, on my machine: name old time/op new time/op delta FMA-8 0.86ns ± 6% 0.70ns ± 5% -18.79% (p=0.000 n=98+97) NonFMA-8 0.61ns ± 5% 0.60ns ± 4% -0.74% (p=0.001 n=100+97) Interestingly, these are both considerably faster than the measurements I took a couple of months ago (1.4ns/2ns). It appears that CL 219131 (clearing VZEROUPPER in asyncPreempt) helped a lot. And FMA is now once again slower than NonFMA, although this change helps it regain some ground. Updates #15808 Updates #36351 Updates #36196 Change-Id: I8a326289a963b1939aaa7eaa2fab2ec536467c7d Reviewed-on: https://go-review.googlesource.com/c/go/+/227238 Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Keith Randall <khr@golang.org>
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