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// Copyright ©2016 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"
// func LinfDist(s, t []float64) float64
TEXT ·LinfDist(SB), NOSPLIT, $0
MOVQ s_base+0(FP), DI // DI = &s
MOVQ t_base+24(FP), SI // SI = &t
MOVQ s_len+8(FP), CX // CX = len(s)
CMPQ t_len+32(FP), CX // CX = max( CX, len(t) )
CMOVQLE t_len+32(FP), CX
PXOR X3, X3 // norm = 0
CMPQ CX, $0 // if CX == 0 { return 0 }
JE l1_end
XORQ AX, AX // i = 0
MOVQ CX, BX
ANDQ $1, BX // BX = CX % 2
SHRQ $1, CX // CX = floor( CX / 2 )
JZ l1_tail_start // if CX == 0 { return 0 }
l1_loop: // Loop unrolled 2x do {
MOVUPS (SI)(AX*8), X0 // X0 = t[i:i+1]
MOVUPS (DI)(AX*8), X1 // X1 = s[i:i+1]
MOVAPS X0, X2
SUBPD X1, X0
SUBPD X2, X1
MAXPD X1, X0 // X0 = max( X0 - X1, X1 - X0 )
MAXPD X0, X3 // norm = max( norm, X0 )
ADDQ $2, AX // i += 2
LOOP l1_loop // } while --CX > 0
CMPQ BX, $0 // if BX == 0 { return }
JE l1_end
l1_tail_start: // Reset loop registers
MOVQ BX, CX // Loop counter: CX = BX
PXOR X0, X0 // reset X0, X1 to break dependencies
PXOR X1, X1
l1_tail:
MOVSD (SI)(AX*8), X0 // X0 = t[i]
MOVSD (DI)(AX*8), X1 // X1 = s[i]
MOVAPD X0, X2
SUBSD X1, X0
SUBSD X2, X1
MAXSD X1, X0 // X0 = max( X0 - X1, X1 - X0 )
MAXSD X0, X3 // norm = max( norm, X0 )
l1_end:
MOVAPS X3, X2
SHUFPD $1, X2, X2
MAXSD X3, X2 // X2 = max( X3[1], X3[0] )
MOVSD X2, ret+48(FP) // return X2
RET
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