From: smasher164 <aindurti@gmail.com>
Date: Thu, 6 Aug 2020 22:37:10 +0000 (-0400)
Subject: math: simplify comparison in FMA when swapping p and z
X-Git-Tag: go1.17beta1~953
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=6f90ee36e9;p=gostls13.git

math: simplify comparison in FMA when swapping p and z

Discovered by Junchen Li on CL 246858, the comparison before p and z are
swapped can be simplified from

    pe < ze || (pe == ze && (pm1 < zm1 || (pm1 == zm1 && pm2 < zm2)))

to

    pe < ze || pe == ze && pm1 < zm1

because zm2 is initialized to 0 before the branch.

Change-Id: Iee92d570038df2b0f8941ef6e422a022654ab2d6
Reviewed-on: https://go-review.googlesource.com/c/go/+/247241
Run-TryBot: Akhil Indurti <aindurti@gmail.com>
Run-TryBot: Emmanuel Odeke <emmanuel@orijtech.com>
Trust: Emmanuel Odeke <emmanuel@orijtech.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
---

diff --git a/src/math/fma.go b/src/math/fma.go
index db78dfa5e1..ca0bf99f21 100644
--- a/src/math/fma.go
+++ b/src/math/fma.go
@@ -128,7 +128,7 @@ func FMA(x, y, z float64) float64 {
 	pe -= int32(is62zero)
 
 	// Swap addition operands so |p| >= |z|
-	if pe < ze || (pe == ze && (pm1 < zm1 || (pm1 == zm1 && pm2 < zm2))) {
+	if pe < ze || pe == ze && pm1 < zm1 {
 		ps, pe, pm1, pm2, zs, ze, zm1, zm2 = zs, ze, zm1, zm2, ps, pe, pm1, pm2
 	}