root/src/pkg/math/hypot_amd64.s

// 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.

#include "../../cmd/ld/textflag.h"

#define PosInf 0x7FF0000000000000
#define NaN 0x7FF8000000000001

// func Hypot(p, q float64) float64
TEXT ·Hypot(SB),NOSPLIT,$0
        // test bits for special cases
        MOVQ    p+0(FP), BX
        MOVQ    $~(1<<63), AX
        ANDQ    AX, BX // p = |p|
        MOVQ    q+8(FP), CX
        ANDQ    AX, CX // q = |q|
        MOVQ    $PosInf, AX
        CMPQ    AX, BX
        JLE     isInfOrNaN
        CMPQ    AX, CX
        JLE     isInfOrNaN
        // hypot = max * sqrt(1 + (min/max)**2)
        MOVQ    BX, X0
        MOVQ    CX, X1
        ORQ     CX, BX
        JEQ     isZero
        MOVAPD  X0, X2
        MAXSD   X1, X0
        MINSD   X2, X1
        DIVSD   X0, X1
        MULSD   X1, X1
        ADDSD   $1.0, X1
        SQRTSD  X1, X1
        MULSD   X1, X0
        MOVSD   X0, ret+16(FP)
        RET
isInfOrNaN:
        CMPQ    AX, BX
        JEQ     isInf
        CMPQ    AX, CX
        JEQ     isInf
        MOVQ    $NaN, AX
        MOVQ    AX, ret+16(FP) // return NaN
        RET
isInf:
        MOVQ    AX, ret+16(FP) // return +Inf
        RET
isZero:
        MOVQ    $0, AX
        MOVQ    AX, ret+16(FP) // return 0
        RET