Use inc reg instead of lea reg, [reg+1]. - #537
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With the path used before we had asm goto, we used setae to mark overflow, and using inc would then cause a partial flags stall. However, now we just use goto directly instead, and this workaround is no longer relevant. Same with the corresponding jnz/dec path. The change was a ~25% win on the microbenchmarks when it was originally rolled out; however, now changing it back has a very small positive effect (Zen 2): name cpu/op cpu/op vs base BM_new_sized_delete/1 6.885n ± 0% 6.756n ± 1% -1.88% (p=0.000 n=50) BM_new_sized_delete/8 6.909n ± 1% 6.889n ± 1% ~ (p=0.071 n=50) BM_new_sized_delete/64 6.925n ± 0% 6.886n ± 1% ~ (p=0.161 n=50) BM_new_sized_delete/512 7.292n ± 1% 7.369n ± 1% ~ (p=0.215 n=50) PiperOrigin-RevId: 967687408
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Use inc reg instead of lea reg, [reg+1].
With the path used before we had asm goto, we used setae
to mark overflow, and using inc would then cause a partial
flags stall. However, now we just use goto directly instead,
and this workaround is no longer relevant. Same with the
corresponding jnz/dec path.
The change was a ~25% win on the microbenchmarks when it was
originally rolled out; however, now changing it back has a
very small positive effect (Zen 2):
name cpu/op cpu/op vs base
BM_new_sized_delete/1 6.885n ± 0% 6.756n ± 1% -1.88% (p=0.000 n=50)
BM_new_sized_delete/8 6.909n ± 1% 6.889n ± 1% ~ (p=0.071 n=50)
BM_new_sized_delete/64 6.925n ± 0% 6.886n ± 1% ~ (p=0.161 n=50)
BM_new_sized_delete/512 7.292n ± 1% 7.369n ± 1% ~ (p=0.215 n=50)