math: 386 FPU hypot

Added 386 FPU version of Hypot; modified all_test.go to test
Hypot with large arguments.  Also edited sqrt.go to remove
Sqrt(0) as a special case.

R=rsc
CC=golang-dev
https://golang.org/cl/186180

diff --git a/src/pkg/math/Makefile b/src/pkg/math/Makefile
index be9b6ff639bf64101507957eff7ae298b31460eb..b10df65300db92b0fbaf0cc80138281b52cb44fd 100644 (file)
--- a/src/pkg/math/Makefile
+++ b/src/pkg/math/Makefile
@@ -15,6 +15,7 @@ OFILES_386=\
        exp_386.$O\
        fabs_386.$O\
        floor_386.$O\
+       hypot_386.$O\
        log_386.$O\
        sin_386.$O\
        sqrt_386.$O\

diff --git a/src/pkg/math/all_test.go b/src/pkg/math/all_test.go
index 15d289be1b48cc5e7ab7ef716dd0baa441c08d64..97c52d3ebef8c2a76c8c3158ccad5c7cbbd17e2d 100644 (file)
--- a/src/pkg/math/all_test.go
+++ b/src/pkg/math/all_test.go
@@ -585,9 +585,9 @@ func TestFmod(t *testing.T) {
 
 func TestHypot(t *testing.T) {
        for i := 0; i < len(vf); i++ {
-               a := Fabs(tanh[i] * Sqrt(2))
-               if f := Hypot(tanh[i], tanh[i]); a != f {
-                       t.Errorf("Hypot(%g, %g) = %g, want %g\n", tanh[i], tanh[i], f, a)
+               a := Fabs(1e200 * tanh[i] * Sqrt(2))
+               if f := Hypot(1e200*tanh[i], 1e200*tanh[i]); !veryclose(a, f) {
+                       t.Errorf("Hypot(%g, %g) = %g, want %g\n", 1e200*tanh[i], 1e200*tanh[i], f, a)
                }
        }
        for i := 0; i < len(vfhypotSC); i++ {

diff --git a/src/pkg/math/hypot_386.s b/src/pkg/math/hypot_386.s
new file mode 100644 (file)
index 0000000..73e4f57
--- /dev/null
+++ b/src/pkg/math/hypot_386.s
@@ -0,0 +1,57 @@
+// Copyright 2010 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.
+
+// func Hypot(x, y float64) float64
+TEXT ·Hypot(SB),7,$0
+// test bits for not-finite
+       MOVL    xh+4(FP), AX   // high word x
+       ANDL    $0x7ff00000, AX
+       CMPL    AX, $0x7ff00000
+       JEQ     not_finite
+       MOVL    yh+12(FP), AX   // high word y
+       ANDL    $0x7ff00000, AX
+       CMPL    AX, $0x7ff00000
+       JEQ     not_finite
+       FMOVD   x+0(FP), F0  // F0=x
+       FABS                 // F0=|x|
+       FMOVD   y+8(FP), F0  // F0=y, F1=|x|
+       FABS                 // F0=|y|, F1=|x|
+       FUCOMI  F0, F1       // compare F0 to F1
+       JCC     2(PC)        // jump if F0 < F1
+       FXCHD   F0, F1       // F0=|x| (larger), F1=|y| (smaller)
+       FTST                 // compare F0 to 0
+       FSTSW   AX
+       ANDW    $0x4000, AX
+       JNE             10(PC)       // jump if F0 = 0
+       FXCHD   F0, F1       // F0=y (smaller), F1=x (larger)
+       FDIVD   F1, F0       // F0=y(=y/x), F1=x
+       FMULD   F0, F0       // F0=y*y, F1=x
+       FLD1                 // F0=1, F1=y*y, F2=x
+       FADDDP  F0, F1       // F0=1+y*y, F1=x
+       FSQRT                // F0=sqrt(1+y*y), F1=x
+       FMULDP  F0, F1       // F0=x*sqrt(1+y*y)
+       FMOVDP  F0, r+16(FP)
+       RET
+       FMOVDP  F0, F1       // F0=0
+       FMOVDP  F0, r+16(FP)
+       RET
+not_finite:
+// test bits for -Inf or +Inf
+       MOVL    xh+4(FP), AX  // high word x
+       ORL     xl+0(FP), AX  // low word x
+       ANDL    $0x7fffffff, AX
+       CMPL    AX, $0x7ff00000
+       JEQ     is_inf
+       MOVL    yh+12(FP), AX  // high word y
+       ORL     yl+8(FP), AX   // low word y
+       ANDL    $0x7fffffff, AX
+       CMPL    AX, $0x7ff00000
+       JEQ     is_inf
+       MOVL    $0x7ff00000, rh+20(FP)  // return NaN = 0x7FF0000000000001
+       MOVL    $0x00000001, rl+16(FP)
+       RET
+is_inf:
+       MOVL    AX, rh+20(FP)  // return +Inf = 0x7FF0000000000000
+       MOVL    $0x00000000, rl+16(FP)
+       RET

diff --git a/src/pkg/math/hypot_decl.go b/src/pkg/math/hypot_decl.go
new file mode 100644 (file)
index 0000000..72603c5
--- /dev/null
+++ b/src/pkg/math/hypot_decl.go
@@ -0,0 +1,7 @@
+// Copyright 2010 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
+
+func Hypot(x, y float64) float64

diff --git a/src/pkg/math/sqrt.go b/src/pkg/math/sqrt.go
index f12e48734f3af19bf9bc23963f0e7326b39264a8..e6bc4680b8dd8b366731c9993465dd74a9b8d21e 100644 (file)
--- a/src/pkg/math/sqrt.go
+++ b/src/pkg/math/sqrt.go
@@ -8,7 +8,6 @@ package math
 //
 // Special cases are:
 //     Sqrt(+Inf) = +Inf
-//     Sqrt(0) = 0
 //     Sqrt(x < 0) = NaN
 //     Sqrt(NaN) = NaN
 func Sqrt(x float64) float64 { return sqrtGo(x) }