diff options
| author | Charlie Dorian <cldorian@gmail.com> | 2015-10-07 18:23:28 -0400 |
|---|---|---|
| committer | Robert Griesemer <gri@golang.org> | 2015-10-09 17:09:16 +0000 |
| commit | 6fed2a68f7adec2a059acc4f702ebe950fdb5ce5 (patch) | |
| tree | 60bd9d62f154738e99e04260147abe3d394393d2 /src | |
| parent | 821b54921a3cba5d853b531d4b03527c01bfc9b4 (diff) | |
| download | go-6fed2a68f7adec2a059acc4f702ebe950fdb5ce5.tar.xz | |
math: Modf(-0) returns -0,-0
Fixes #12867
Change-Id: I8ba81c622bce2a77a6142f941603198582eaf8a4
Reviewed-on: https://go-review.googlesource.com/15570
Reviewed-by: Robert Griesemer <gri@golang.org>
Diffstat (limited to 'src')
| -rw-r--r-- | src/math/all_test.go | 4 | ||||
| -rw-r--r-- | src/math/modf.go | 5 | ||||
| -rw-r--r-- | src/math/modf_386.s | 13 |
3 files changed, 20 insertions, 2 deletions
diff --git a/src/math/all_test.go b/src/math/all_test.go index e18e45e020..53e84765cb 100644 --- a/src/math/all_test.go +++ b/src/math/all_test.go @@ -447,7 +447,7 @@ var log2 = []float64{ var modf = [][2]float64{ {4.0000000000000000e+00, 9.7901192488367350108546816e-01}, {7.0000000000000000e+00, 7.3887247457810456552351752e-01}, - {0.0000000000000000e+00, -2.7688005719200159404635997e-01}, + {Copysign(0, -1), -2.7688005719200159404635997e-01}, {-5.0000000000000000e+00, -1.060361827107492160848778e-02}, {9.0000000000000000e+00, 6.3629370719841737980004837e-01}, {2.0000000000000000e+00, 9.2637723924396464525443662e-01}, @@ -1356,11 +1356,13 @@ var log1pSC = []float64{ var vfmodfSC = []float64{ Inf(-1), + Copysign(0, -1), Inf(1), NaN(), } var modfSC = [][2]float64{ {Inf(-1), NaN()}, // [2]float64{Copysign(0, -1), Inf(-1)}, + {Copysign(0, -1), Copysign(0, -1)}, {Inf(1), NaN()}, // [2]float64{0, Inf(1)}, {NaN(), NaN()}, } diff --git a/src/math/modf.go b/src/math/modf.go index 1e8376a938..81cb8b5a9c 100644 --- a/src/math/modf.go +++ b/src/math/modf.go @@ -14,9 +14,12 @@ func Modf(f float64) (int float64, frac float64) func modf(f float64) (int float64, frac float64) { if f < 1 { - if f < 0 { + switch { + case f < 0: int, frac = Modf(-f) return -int, -frac + case f == 0: + return f, f // Return -0, -0 when f == -0 } return 0, f } diff --git a/src/math/modf_386.s b/src/math/modf_386.s index 3debd3b95d..d549f1d1a0 100644 --- a/src/math/modf_386.s +++ b/src/math/modf_386.s @@ -6,6 +6,19 @@ // func Modf(f float64) (int float64, frac float64) TEXT ·Modf(SB),NOSPLIT,$0 + // special case for f == -0.0 + MOVL f+4(FP), DX // high word + MOVL f+0(FP), AX // low word + CMPL DX, $(1<<31) // beginning of -0.0 + JNE notNegativeZero + CMPL AX, $0 // could be denormalized + JNE notNegativeZero + MOVL AX, int+8(FP) + MOVL DX, int+12(FP) + MOVL AX, frac+16(FP) + MOVL DX, frac+20(FP) + RET +notNegativeZero: FMOVD f+0(FP), F0 // F0=f FMOVD F0, F1 // F0=f, F1=f FSTCW -2(SP) // save old Control Word |