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// Copyright ©2019 The Gonum Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// +build !noasm,!gccgo,!safe
#include "textflag.h"
#define SUMSQ X0
#define ABSX X1
#define SCALE X2
#define ZERO X3
#define TMP X4
#define ABSMASK X5
#define INF X7
#define INFMASK X11
#define NANMASK X12
#define IDX AX
#define X_ DI
#define Y_ BX
#define LEN SI
#define ABSMASK_DATA l2nrodata<>+0(SB)
#define INF_DATA l2nrodata<>+8(SB)
#define NAN_DATA l2nrodata<>+16(SB)
// AbsMask
DATA l2nrodata<>+0(SB)/8, $0x7FFFFFFFFFFFFFFF
// Inf
DATA l2nrodata<>+8(SB)/8, $0x7FF0000000000000
// NaN
DATA l2nrodata<>+16(SB)/8, $0xFFF8000000000000
GLOBL l2nrodata<>+0(SB), RODATA, $24
// L2DistanceUnitary returns the L2-norm of x-y.
// func L2DistanceUnitary(x,y []float64) (norm float64)
TEXT ·L2DistanceUnitary(SB), NOSPLIT, $0
MOVQ x_base+0(FP), X_
MOVQ y_base+24(FP), Y_
PXOR ZERO, ZERO
MOVQ x_len+8(FP), LEN // LEN = min( len(x), len(y) )
CMPQ y_len+32(FP), LEN
CMOVQLE y_len+32(FP), LEN
CMPQ LEN, $0 // if LEN == 0 { return 0 }
JZ retZero
PXOR INFMASK, INFMASK
PXOR NANMASK, NANMASK
MOVSD $1.0, SUMSQ // ssq = 1
XORPS SCALE, SCALE
MOVSD ABSMASK_DATA, ABSMASK
MOVSD INF_DATA, INF
XORQ IDX, IDX // idx == 0
initZero: // for ;x[i]==0; i++ {}
// Skip all leading zeros, to avoid divide by zero NaN
MOVSD (X_)(IDX*8), ABSX // absxi = x[i]
SUBSD (Y_)(IDX*8), ABSX // absxi = x[i]-y[i]
UCOMISD ABSX, ZERO
JP retNaN // if isNaN(absxi) { return NaN }
JNE loop // if absxi != 0 { goto loop }
INCQ IDX // i++
CMPQ IDX, LEN
JE retZero // if i == LEN { return 0 }
JMP initZero
loop:
MOVSD (X_)(IDX*8), ABSX // absxi = x[i]
SUBSD (Y_)(IDX*8), ABSX // absxi = x[i]-y[i]
MOVUPS ABSX, TMP
CMPSD ABSX, TMP, $3
ORPD TMP, NANMASK // NANMASK = NANMASK | IsNaN(absxi)
MOVSD INF, TMP
ANDPD ABSMASK, ABSX // absxi == Abs(absxi)
CMPSD ABSX, TMP, $0
ORPD TMP, INFMASK // INFMASK = INFMASK | IsInf(absxi)
UCOMISD SCALE, ABSX
JA adjScale // IF SCALE > ABSXI { goto adjScale }
DIVSD SCALE, ABSX // absxi = scale / absxi
MULSD ABSX, ABSX // absxi *= absxi
ADDSD ABSX, SUMSQ // sumsq += absxi
INCQ IDX // i++
CMPQ IDX, LEN
JNE loop // if i < LEN { continue }
JMP retSum // if i == LEN { goto retSum }
adjScale: // Scale > Absxi
DIVSD ABSX, SCALE // tmp = absxi / scale
MULSD SCALE, SUMSQ // sumsq *= tmp
MULSD SCALE, SUMSQ // sumsq *= tmp
ADDSD $1.0, SUMSQ // sumsq += 1
MOVUPS ABSX, SCALE // scale = absxi
INCQ IDX // i++
CMPQ IDX, LEN
JNE loop // if i < LEN { continue }
retSum: // Calculate return value
SQRTSD SUMSQ, SUMSQ // sumsq = sqrt(sumsq)
MULSD SCALE, SUMSQ // sumsq += scale
MOVQ SUMSQ, R10 // tmp = sumsq
UCOMISD ZERO, INFMASK
CMOVQPS INF_DATA, R10 // if INFMASK { tmp = INF }
UCOMISD ZERO, NANMASK
CMOVQPS NAN_DATA, R10 // if NANMASK { tmp = NaN }
MOVQ R10, norm+48(FP) // return tmp
RET
retZero:
MOVSD ZERO, norm+48(FP) // return 0
RET
retNaN:
MOVSD NAN_DATA, TMP // return NaN
MOVSD TMP, norm+48(FP)
RET
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