math: replace assembly implementations of Abs with pure Go version

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>

diff --git a/src/math/abs.go b/src/math/abs.go
index bc41a6d6b50cba6e143acdfecf1726d910911bc1..e35e4da792a6a1d2c2ed9598474175675a6c9ee8 100644 (file)
--- a/src/math/abs.go
+++ b/src/math/abs.go
@@ -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

diff --git a/src/math/abs_386.s b/src/math/abs_386.s
deleted file mode 100644 (file)
index f30a439..0000000
--- a/src/math/abs_386.s
+++ /dev/null
@@ -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

diff --git a/src/math/abs_amd64.s b/src/math/abs_amd64.s
deleted file mode 100644 (file)
index 0424eb5..0000000
--- a/src/math/abs_amd64.s
+++ /dev/null
@@ -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

diff --git a/src/math/abs_amd64p32.s b/src/math/abs_amd64p32.s
deleted file mode 100644 (file)
index 08c8c6b..0000000
--- a/src/math/abs_amd64p32.s
+++ /dev/null
@@ -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"

diff --git a/src/math/abs_arm.s b/src/math/abs_arm.s
deleted file mode 100644 (file)
index bfa77eb..0000000
--- a/src/math/abs_arm.s
+++ /dev/null
@@ -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

diff --git a/src/math/abs_arm64.s b/src/math/abs_arm64.s
deleted file mode 100644 (file)
index d8f9382..0000000
--- a/src/math/abs_arm64.s
+++ /dev/null
@@ -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

diff --git a/src/math/abs_ppc64x.s b/src/math/abs_ppc64x.s
deleted file mode 100644 (file)
index 06effb4..0000000
--- a/src/math/abs_ppc64x.s
+++ /dev/null
@@ -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