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Adds tests for sign bit preservation for moremath rounding functions. (#590)

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Signed-off-by: Anuraag Agrawal <anuraaga@gmail.com>
This commit is contained in:
Anuraag Agrawal
2022-05-23 18:23:26 +09:00
committed by GitHub
parent d036b936c9
commit 5ed31d3c49
2 changed files with 24 additions and 2 deletions
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4
internal/moremath/moremath.go
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@@ -57,7 +57,7 @@ func WasmCompatMax(x, y float64) float64 {
// See https://llvm.org/docs/LangRef.html#llvm-rint-intrinsic.
func WasmCompatNearestF32(f float32) float32 {
// TODO: look at https://github.com/bytecodealliance/wasmtime/pull/2171 and reconsider this algorithm
if f != -0 && f != 0 {
if f != 0 {
ceil := float32(math.Ceil(float64(f)))
floor := float32(math.Floor(float64(f)))
distToCeil := math.Abs(float64(f - ceil))
@@ -82,7 +82,7 @@ func WasmCompatNearestF32(f float32) float32 {
// See https://llvm.org/docs/LangRef.html#llvm-rint-intrinsic.
func WasmCompatNearestF64(f float64) float64 {
// TODO: look at https://github.com/bytecodealliance/wasmtime/pull/2171 and reconsider this algorithm
if f != -0 && f != 0 {
if f != 0 {
ceil := math.Ceil(f)
floor := math.Floor(f)
distToCeil := math.Abs(f - ceil)

22
internal/moremath/moremath_test.go
View File

@@ -39,6 +39,17 @@ func TestWasmCompatNearestF32(t *testing.T) {
// This is the diff from math.Round.
require.Equal(t, WasmCompatNearestF32(-4.5), float32(-4.0))
require.Equal(t, float32(math.Round(-4.5)), float32(-5.0))
// Prevent constant folding by using two variables. -float32(0) is not actually negative.
// https://github.com/golang/go/issues/2196
zero := float32(0)
negZero := -zero
// Sign bit preserved for +/- zero
require.False(t, math.Signbit(float64(zero)))
require.False(t, math.Signbit(float64(WasmCompatNearestF32(zero))))
require.True(t, math.Signbit(float64(negZero)))
require.True(t, math.Signbit(float64(WasmCompatNearestF32(negZero))))
}
func TestWasmCompatNearestF64(t *testing.T) {
@@ -47,4 +58,15 @@ func TestWasmCompatNearestF64(t *testing.T) {
// This is the diff from math.Round.
require.Equal(t, WasmCompatNearestF64(-4.5), -4.0)
require.Equal(t, math.Round(-4.5), -5.0)
// Prevent constant folding by using two variables. -float64(0) is not actually negative.
// https://github.com/golang/go/issues/2196
zero := float64(0)
negZero := -zero
// Sign bit preserved for +/- zero
require.False(t, math.Signbit(zero))
require.False(t, math.Signbit(WasmCompatNearestF64(zero)))
require.True(t, math.Signbit(negZero))
require.True(t, math.Signbit(WasmCompatNearestF64(negZero)))
}