math: add Cbrt and Sincos; x87 versions of Sincos, Frexp, Ldexp
Added special condition and benchmarks for Cbrt, Sincos. Took Frexp and Ldexp out of bits.go.
R=rsc
CC=golang-dev
https://golang.org/cl/206084
diff --git a/src/pkg/math/ldexp.go b/src/pkg/math/ldexp.go
new file mode 100644
index 0000000..e822370
--- /dev/null
+++ b/src/pkg/math/ldexp.go
@@ -0,0 +1,30 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+// Ldexp is the inverse of Frexp.
+// It returns frac × 2<sup>exp</sup>.
+func Ldexp(frac float64, exp int) float64 {
+ // TODO(rsc): Remove manual inlining of IsNaN, IsInf
+ // when compiler does it for us
+ // special cases
+ if frac != frac { // IsNaN(frac)
+ return NaN()
+ }
+ x := Float64bits(frac)
+ exp += int(x>>shift) & mask
+ if exp <= 0 {
+ return 0 // underflow
+ }
+ if exp >= mask { // overflow
+ if frac < 0 {
+ return Inf(-1)
+ }
+ return Inf(1)
+ }
+ x &^= mask << shift
+ x |= uint64(exp) << shift
+ return Float64frombits(x)
+}
