math: faster, easier to inline IsNaN, IsInf
R=r
CC=golang-dev
https://golang.org/cl/180046
diff --git a/src/pkg/math/bits.go b/src/pkg/math/bits.go
index 65eabfd..9f93a19 100644
--- a/src/pkg/math/bits.go
+++ b/src/pkg/math/bits.go
@@ -29,8 +29,11 @@
// IsNaN returns whether f is an IEEE 754 ``not-a-number'' value.
func IsNaN(f float64) (is bool) {
- x := Float64bits(f)
- return uint32(x>>shift)&mask == mask && x != uvinf && x != uvneginf
+ // IEEE 754 says that only NaNs satisfy f != f.
+ // To avoid the floating-point hardware, could use:
+ // x := Float64bits(f);
+ // return uint32(x>>shift)&mask == mask && x != uvinf && x != uvneginf
+ return f != f
}
// IsInf returns whether f is an infinity, according to sign.
@@ -38,8 +41,11 @@
// If sign < 0, IsInf returns whether f is negative infinity.
// If sign == 0, IsInf returns whether f is either infinity.
func IsInf(f float64, sign int) bool {
- x := Float64bits(f)
- return sign >= 0 && x == uvinf || sign <= 0 && x == uvneginf
+ // Test for infinity by comparing against maximum float.
+ // To avoid the floating-point hardware, could use:
+ // x := Float64bits(f);
+ // return sign >= 0 && x == uvinf || sign <= 0 && x == uvneginf;
+ return sign >= 0 && f > MaxFloat64 || sign <= 0 && f < -MaxFloat64
}
// Frexp breaks f into a normalized fraction
