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| author | LE Manh Cuong <cuong.manhle.vn@gmail.com> | 2019-05-08 17:02:23 +0700 |
|---|---|---|
| committer | Daniel Martí <mvdan@mvdan.cc> | 2019-08-27 18:01:16 +0000 |
| commit | c5f142fa9fb6e00b0877ba4b6e9ab77d22ac50cd (patch) | |
| tree | 3f958cb07e741c3abe5597ef81c15b6f4e2c1491 /test/codegen/bits.go | |
| parent | ae68a912725e5a3a0482bc5945687663f2ddafe3 (diff) | |
| download | go-git-c5f142fa9fb6e00b0877ba4b6e9ab77d22ac50cd.tar.gz | |
cmd/compile: optimize bitset tests
The assembly output for x & c == c, where c is power of 2:
MOVQ "".set+8(SP), AX
ANDQ $8, AX
CMPQ AX, $8
SETEQ "".~r2+24(SP)
With optimization using bitset:
MOVQ "".set+8(SP), AX
BTL $3, AX
SETCS "".~r2+24(SP)
output less than 1 instruction.
However, there is no speed improvement:
name old time/op new time/op delta
AllBitSet-8 0.35ns ± 0% 0.35ns ± 0% ~ (all equal)
Fixes #31904
Change-Id: I5dca4e410bf45716ed2145e3473979ec997e35d4
Reviewed-on: https://go-review.googlesource.com/c/go/+/175957
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Diffstat (limited to 'test/codegen/bits.go')
| -rw-r--r-- | test/codegen/bits.go | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/test/codegen/bits.go b/test/codegen/bits.go index 65d57c8f9f..18f9daf7cf 100644 --- a/test/codegen/bits.go +++ b/test/codegen/bits.go @@ -314,3 +314,15 @@ func op_orn(x, y uint32) uint32 { // arm64:`ORN\t`,-`ORR` return x | ^y } + +// check bitsets +func bitSetPowerOf2Test(x int) bool { + // amd64:"BTL\t[$]3" + return x&8 == 8 +} + +func bitSetTest(x int) bool { + // amd64:"ANDQ\t[$]9, AX" + // amd64:"CMPQ\tAX, [$]9" + return x&9 == 9 +} |