1// Copyright ©2016 The Gonum Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// +build !noasm,!gccgo,!safe
6
7#include "textflag.h"
8
9// func L1Dist(s, t []float64) float64
10TEXT ·L1Dist(SB), NOSPLIT, $0
11	MOVQ    s_base+0(FP), DI  // DI = &s
12	MOVQ    t_base+24(FP), SI // SI = &t
13	MOVQ    s_len+8(FP), CX   // CX = len(s)
14	CMPQ    t_len+32(FP), CX  // CX = max( CX, len(t) )
15	CMOVQLE t_len+32(FP), CX
16	PXOR    X3, X3            // norm = 0
17	CMPQ    CX, $0            // if CX == 0 { return 0 }
18	JE      l1_end
19	XORQ    AX, AX            // i = 0
20	MOVQ    CX, BX
21	ANDQ    $1, BX            // BX = CX % 2
22	SHRQ    $1, CX            // CX = floor( CX / 2 )
23	JZ      l1_tail_start     // if CX == 0 { return 0 }
24
25l1_loop: // Loop unrolled 2x  do {
26	MOVUPS (SI)(AX*8), X0 // X0 = t[i:i+1]
27	MOVUPS (DI)(AX*8), X1 // X1 = s[i:i+1]
28	MOVAPS X0, X2
29	SUBPD  X1, X0
30	SUBPD  X2, X1
31	MAXPD  X1, X0         // X0 = max( X0 - X1, X1 - X0 )
32	ADDPD  X0, X3         // norm += X0
33	ADDQ   $2, AX         // i += 2
34	LOOP   l1_loop        // } while --CX > 0
35	CMPQ   BX, $0         // if BX == 0 { return }
36	JE     l1_end
37
38l1_tail_start: // Reset loop registers
39	MOVQ BX, CX // Loop counter: CX = BX
40	PXOR X0, X0 // reset X0, X1 to break dependencies
41	PXOR X1, X1
42
43l1_tail:
44	MOVSD  (SI)(AX*8), X0 // X0 = t[i]
45	MOVSD  (DI)(AX*8), X1 // x1 = s[i]
46	MOVAPD X0, X2
47	SUBSD  X1, X0
48	SUBSD  X2, X1
49	MAXSD  X1, X0         // X0 = max( X0 - X1, X1 - X0 )
50	ADDSD  X0, X3         // norm += X0
51
52l1_end:
53	MOVAPS X3, X2
54	SHUFPD $1, X2, X2
55	ADDSD  X3, X2         // X2 = X3[1] + X3[0]
56	MOVSD  X2, ret+48(FP) // return X2
57	RET
58
59