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math: replace assembly implementations of Abs with pure Go version

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The compiler can do a fine job, and can also inline it.

From Jeremy Jackins's observation and rsc's recommendation in thread:

"Pure Go math.Abs outperforms assembly version"
https://groups.google.com/forum/#!topic/golang-dev/nP5mWvwAXZo

Updates #13095

Change-Id: I3066f8eaa327bb403173b29791cc8661d7c0532c
Reviewed-on: https://go-review.googlesource.com/16444
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Brad Fitzpatrick 2015-10-29 15:13:58 +00:00
parent 51586aadfb
commit 6f8a66536b
7 changed files with 4 additions and 72 deletions
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7
src/math/abs.go
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@ -9,9 +9,10 @@ package math
// Special cases are:
// Abs(±Inf) = +Inf
// Abs(NaN) = NaN
func Abs(x float64) float64
func abs(x float64) float64 {
func Abs(x float64) float64 {
// TODO: once golang.org/issue/13905 is fixed, change this to:
// return Float64frombits(Float64bits(x) &^ (1 << 63))
// But for now, this generates better code and can also be inlined:
switch {
case x < 0:
return -x

12
src/math/abs_386.s
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@ -1,12 +0,0 @@
// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#include "textflag.h"
// func Abs(x float64) float64
TEXT ·Abs(SB),NOSPLIT,$0
FMOVD x+0(FP), F0 // F0=x
FABS // F0=|x|
FMOVDP F0, ret+8(FP)
RET

14
src/math/abs_amd64.s
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@ -1,14 +0,0 @@
// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#include "textflag.h"
// func Abs(x float64) float64
TEXT ·Abs(SB),NOSPLIT,$0
MOVQ $(1<<63), BX
MOVQ BX, X0 // movsd $(-0.0), x0
MOVSD x+0(FP), X1
ANDNPD X1, X0
MOVSD X0, ret+8(FP)
RET

5
src/math/abs_amd64p32.s
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@ -1,5 +0,0 @@
// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#include "abs_amd64.s"

13
src/math/abs_arm.s
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@ -1,13 +0,0 @@
// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#include "textflag.h"
TEXT ·Abs(SB),NOSPLIT,$0
MOVW x_lo+0(FP), R0
MOVW x_hi+4(FP), R1
AND $((1<<31)-1), R1
MOVW R0, ret_lo+8(FP)
MOVW R1, ret_hi+12(FP)
RET

11
src/math/abs_arm64.s
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@ -1,11 +0,0 @@
// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#include "textflag.h"
TEXT ·Abs(SB),NOSPLIT,$0-16
FMOVD x+0(FP), F3
FABSD F3, F3
FMOVD F3, ret+8(FP)
RET

14
src/math/abs_ppc64x.s
View File

@ -1,14 +0,0 @@
// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// +build ppc64 ppc64le
#include "textflag.h"
TEXT ·Abs(SB),NOSPLIT,$0-16
MOVD x+0(FP), R3
MOVD $((1<<63)-1), R4
AND R4, R3
MOVD R3, ret+8(FP)
RET