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math: correct Atan2(±y,+∞) = ±0 on s390x

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The s390x assembly implementation was previously only handling this
case correctly for x = -Pi.  Update the special case handling for
any y.

Fixes #35446

Change-Id: I355575e9ec8c7ce8bd9db10d74f42a22f39a2f38
Reviewed-on: https://go-review.googlesource.com/c/go/+/223420
Run-TryBot: Brian Kessler <brian.m.kessler@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Munday <mike.munday@ibm.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Brian Kessler 2020-03-13 23:24:38 -06:00 committed by Robert Griesemer
parent 97585092f5
commit 6b6414cab4
2 changed files with 11 additions and 4 deletions
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4
src/math/all_test.go
View File

@ -827,6 +827,8 @@ var vfatan2SC = [][2]float64{
{+Pi, Inf(-1)},
{+Pi, 0},
{+Pi, Inf(1)},
{1.0, Inf(1)},
{-1.0, Inf(1)},
{+Pi, NaN()},
{Inf(1), Inf(-1)},
{Inf(1), -Pi},
@ -864,6 +866,8 @@ var atan2SC = []float64{
Pi, // atan2(+Pi, -Inf)
Pi / 2, // atan2(+Pi, +0)
0, // atan2(+Pi, +Inf)
0, // atan2(+1, +Inf)
Copysign(0, -1), // atan2(-1, +Inf)
NaN(), // atan2(+Pi, NaN)
3 * Pi / 4, // atan2(+Inf, -Inf)
Pi / 2, // atan2(+Inf, -Pi)

11
src/math/atan2_s390x.s
View File

@ -134,9 +134,9 @@ yIsPosInf:
MOVD $NegInf, R3
CMPUBEQ R3, R1, negInfPosInf
//special case Atan2(-Pi, +Inf) = Pi
MOVD $NegPi, R3
CMPUBEQ R3, R1, negPiPosInf
//special case Atan2(x, +Inf) = Copysign(0, x)
CMPBLT R1, $0, returnNegZero
BR returnPosZero
Normal:
FMOVD x+0(FP), F0
@ -288,7 +288,10 @@ negInfPosInf:
MOVD $NegPiDiv4, R1
MOVD R1, ret+16(FP)
RET
negPiPosInf:
returnNegZero:
MOVD $NegZero, R1
MOVD R1, ret+16(FP)
RET
returnPosZero:
MOVD $0, ret+16(FP)
RET