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perf: use bits.Len64 instead of bsr #129

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merged 1 commit into from
Apr 13, 2022
Merged

perf: use bits.Len64 instead of bsr #129

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19 changes: 0 additions & 19 deletions lang/mcache/bsr_amd64.go
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27 changes: 0 additions & 27 deletions lang/mcache/bsr_amd64.s
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27 changes: 0 additions & 27 deletions lang/mcache/bsr_other.go
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6 changes: 6 additions & 0 deletions lang/mcache/utils.go
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,12 @@

package mcache

import "math/bits"

func bsr(x int) int {
return bits.Len(uint(x)) - 1
}

func isPowerOfTwo(x int) bool {
return (x & (-x)) == x
}
10 changes: 10 additions & 0 deletions lang/mcache/bsr_test.go → lang/mcache/utils_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -26,3 +26,13 @@ func TestBsr(t *testing.T) {
assert.Equal(t, bsr((1<<10)-1), 9)
assert.Equal(t, bsr((1<<30)+(1<<19)+(1<<16)+(1<<1)), 30)
}

func BenchmarkBsr(b *testing.B) {
num := (1 << 30) + (1 << 19) + (1 << 16) + (1 << 1)

b.ReportAllocs()
b.ResetTimer()
for i := 0; i < b.N; i++ {
_ = bsr(num + i)
}
}