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The Go programming language
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a92ca51507
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Wayne Zuo a92ca51507 cmd/compile: use LZCNT instruction for GOAMD64>=3 
LZCNT is similar to BSR, but BSR(x) is undefined when x == 0, so using
LZCNT can avoid a special case for zero input. Except that case,
LZCNTQ(x) == 63-BSRQ(x) and LZCNTL(x) == 31-BSRL(x).

And according to https://www.agner.org/optimize/instruction_tables.pdf,
LZCNT instructions are much faster than BSR on AMD CPU.

name              old time/op  new time/op  delta
LeadingZeros-8    0.91ns ± 1%  0.80ns ± 7%  -11.68%  (p=0.000 n=9+9)
LeadingZeros8-8   0.98ns ±15%  0.91ns ± 1%   -7.34%  (p=0.000 n=9+9)
LeadingZeros16-8  0.94ns ± 3%  0.92ns ± 2%   -2.36%  (p=0.001 n=10+10)
LeadingZeros32-8  0.89ns ± 1%  0.78ns ± 2%  -12.49%  (p=0.000 n=10+10)
LeadingZeros64-8  0.92ns ± 1%  0.78ns ± 1%  -14.48%  (p=0.000 n=10+10)

Change-Id: I125147fe3d6994a4cfe558432780408e9a27557a
Reviewed-on: https://go-review.googlesource.com/c/go/+/396794
Reviewed-by: Keith Randall <khr@golang.org>
Trust: Emmanuel Odeke <emmanuel@orijtech.com>
Run-TryBot: Emmanuel Odeke <emmanuel@orijtech.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
2022-04-04 04:01:17 +00:00
.github .github: remove duplicate security link 2022-01-07 17:55:09 +00:00
api strconv: quote rune 007F as \x7f, not \u007f 2022-03-31 20:37:15 +00:00
doc net: support error.Is of network errors and context errors 2022-04-03 15:43:15 +00:00
lib/time lib/time, time/tzdata: update to 2021e 2021-11-11 05:16:39 +00:00
misc cmd/cgo: retain original file paths in godefs generated comment 2022-04-03 07:18:10 +00:00
src cmd/compile: use LZCNT instruction for GOAMD64>=3 2022-04-04 04:01:17 +00:00
test cmd/compile: use LZCNT instruction for GOAMD64>=3 2022-04-04 04:01:17 +00:00
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AUTHORS A+C: change email of Ben Shi (individual CLA) 2022-03-22 16:02:31 +00:00
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README.md

The Go Programming Language

Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.

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