[PATCH] D118534: [X86] Introduce more common modern tunings into `generic`

Fri Feb 4 01:22:25 PST 2022

pengfei added a comment.

In D118534#3295994 <https://reviews.llvm.org/D118534#3295994>, @lebedev.ri wrote:

> Please split Znver changes into a separate review.
> At least for znver3, i'm not really confident that `fsqrt` is fast,
> https://www.agner.org/optimize/instruction_tables.pdf says ~25cy,
> while NR takes ~19cy: https://godbolt.org/z/rK9ra4hse

Although Agner's table says it's 8~21 and 22 for znver1 and znver2 respectively, the mca shows they are worse than znver3. Is it a bug in schedule model? I'd like to leave Znver tuning as is given I'm not familiar with them.

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https://reviews.llvm.org/D118534