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 golang#13095 Change-Id: I3066f8eaa327bb403173b29791cc8661d7c0532c Reviewed-on: https://go-review.googlesource.com/16444 Reviewed-by: Ian Lance Taylor <[email protected]> Run-TryBot: Brad Fitzpatrick <[email protected]> TryBot-Result: Gobot Gobot <[email protected]>
anthonyfok · Oct 29, 2015 · 6f8a665 · 6f8a665
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commit 6f8a665
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Showing 7 changed files with 4 additions and 72 deletions.
diff --git 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
diff --git a/src/math/abs_amd64.s b/src/math/abs_amd64.s
diff --git a/src/math/abs_amd64p32.s b/src/math/abs_amd64p32.s
diff --git a/src/math/abs_arm.s b/src/math/abs_arm.s
diff --git a/src/math/abs_arm64.s b/src/math/abs_arm64.s
diff --git a/src/math/abs_ppc64x.s b/src/math/abs_ppc64x.s