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BUGS.md: update the status of #80657 and the data for #80835 - #18
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Issue 80657 is closed now that CL 839405 is in tip; 1.27.3 still crashes, which flag_methods_ice.txt pins. The section on 80835 said the effect on Intel was unknown. Others have since measured it in the issue: Skylake-X pays 2x to 3x on scalar code after an AVX-512 kernel, Sapphire Rapids and Granite Rapids lose about 15 points of peak on a kernel until ClearAVXUpperBits is added, and adding it to every short leaf function costs about 0.8 ns per call. Add those, along with loopvec's own measurements: GOAMD64=v3 does not remove the penalty, the clear costs nothing after a pure vector loop, and one rewritten fill made scalar loops in gonum's Dlantb 7x slower. loopvec does not emit the clear yet, so say "none yet".
mauri870
enabled auto-merge (squash)
November 4, 2026 00:22
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Issue 80657 is closed now that CL 839405 is in tip; 1.27.3 still
crashes, which flag_methods_ice.txt pins.
The section on 80835 said the effect on Intel was unknown. Others have
since measured it in the issue: Skylake-X pays 2x to 3x on scalar code
after an AVX-512 kernel, Sapphire Rapids and Granite Rapids lose about
15 points of peak on a kernel until ClearAVXUpperBits is added, and
adding it to every short leaf function costs about 0.8 ns per call.
Add those, along with loopvec's own measurements: GOAMD64=v3 does not
remove the penalty, the clear costs nothing after a pure vector loop,
and one rewritten fill made scalar loops in gonum's Dlantb 7x slower.
loopvec does not emit the clear yet, so say "none yet".