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math/big: replace local versions of bitLen, nlz with math/bits versions

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Verified that BenchmarkBitLen time went down from 2.25 ns/op to 0.65 ns/op
an a 2.3 GHz Intel Core i7, before removing that benchmark (now covered by
math/bits benchmarks).

Change-Id: I3890bb7d1889e95b9a94bd68f0bdf06f1885adeb
Reviewed-on: https://go-review.googlesource.com/38464
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Robert Griesemer 2017-03-23 10:54:08 -07:00
parent 536a2257fb
commit 70ea0ec30f
17 changed files with 17 additions and 141 deletions
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5
src/math/big/float.go
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@ -14,6 +14,7 @@ package big
import (
"fmt"
"math"
"math/bits"
)
const debugFloat = false // enable for debugging
@ -498,8 +499,8 @@ func (z *Float) setBits64(neg bool, x uint64) *Float {
}
// x != 0
z.form = finite
s := nlz64(x)
z.mant = z.mant.setUint64(x << s)
s := bits.LeadingZeros64(x)
z.mant = z.mant.setUint64(x << uint(s))
z.exp = int32(64 - s) // always fits
if z.prec < 64 {
z.round(0)