runtime: convert float64toint64, float64touint64 to Go

This is a very dumb translation to keep the code as close to the original C as possible.

LGTM=rsc
R=khr, minux, rsc, josharian
CC=golang-codereviews
https://golang.org/cl/126490043

diff --git a/src/pkg/runtime/vlrt.go b/src/pkg/runtime/vlrt.go
new file mode 100644 (file)
index 0000000..64154fc
--- /dev/null
+++ b/src/pkg/runtime/vlrt.go
@@ -0,0 +1,91 @@
+// Inferno's libkern/vlrt-arm.c
+// http://code.google.com/p/inferno-os/source/browse/libkern/vlrt-arm.c
+//
+//         Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
+//         Revisions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com).  All rights reserved.
+//         Portions Copyright 2009 The Go Authors. All rights reserved.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+// +build arm
+
+package runtime
+
+import "unsafe"
+
+func float64toint64(d float64, y uint64) {
+       _d2v(&y, d)
+}
+
+func float64touint64(d float64, y uint64) {
+       _d2v(&y, d)
+}
+
+const (
+       sign64 = 1 << (64 - 1)
+)
+
+func _d2v(y *uint64, d float64) {
+       x := *(*uint64)(unsafe.Pointer(&d))
+
+       xhi := uint32(x>>32)&0xfffff | 0x100000
+       xlo := uint32(x)
+       sh := 1075 - int32(uint32(x>>52)&0x7ff)
+
+       var ylo, yhi uint32
+       if sh >= 0 {
+               sh := uint32(sh)
+               /* v = (hi||lo) >> sh */
+               if sh < 32 {
+                       if sh == 0 {
+                               ylo = xlo
+                               yhi = xhi
+                       } else {
+                               ylo = xlo>>sh | xhi<<(32-sh)
+                               yhi = xhi >> sh
+                       }
+               } else {
+                       if sh == 32 {
+                               ylo = xhi
+                       } else if sh < 64 {
+                               ylo = xhi >> (sh - 32)
+                       }
+               }
+       } else {
+               /* v = (hi||lo) << -sh */
+               sh := uint32(-sh)
+               if sh <= 11 {
+                       ylo = xlo << sh
+                       yhi = xhi<<sh | xlo>>(32-sh)
+               } else {
+                       /* overflow */
+                       yhi = uint32(d) /* causes something awful */
+               }
+       }
+       if x&sign64 != 0 {
+               if ylo != 0 {
+                       ylo = -ylo
+                       yhi = ^yhi
+               } else {
+                       yhi = -yhi
+               }
+       }
+
+       *y = uint64(yhi)<<32 | uint64(ylo)
+}

diff --git a/src/pkg/runtime/vlrt_arm.c b/src/pkg/runtime/vlrt_arm.c
index 48ae08be32842804b5748e0021d4d1f24e5fa413..5e7807f4557f80d8f9d828bc9911908a7c838418 100644 (file)
--- a/src/pkg/runtime/vlrt_arm.c
+++ b/src/pkg/runtime/vlrt_arm.c
@@ -128,18 +128,6 @@ _f2v(Vlong *y, float f)
        _d2v(y, f);
 }
 
-void
-runtime·float64toint64(double d, Vlong y)
-{
-       _d2v(&y, d);
-}
-
-void
-runtime·float64touint64(double d, Vlong y)
-{
-       _d2v(&y, d);
-}
-
 double
 _ul2d(ulong u)
 {