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// Copyright 2018 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 "go_asm.h"
#include "textflag.h"
TEXT ·Index(SB),NOSPLIT,$0-56
MOVD a_base+0(FP), R0
MOVD a_len+8(FP), R1
MOVD b_base+24(FP), R2
MOVD b_len+32(FP), R3
MOVD $ret+48(FP), R9
B indexbody<>(SB)
TEXT ·IndexString(SB),NOSPLIT,$0-40
MOVD a_base+0(FP), R0
MOVD a_len+8(FP), R1
MOVD b_base+16(FP), R2
MOVD b_len+24(FP), R3
MOVD $ret+32(FP), R9
B indexbody<>(SB)
// input:
// R0: haystack
// R1: length of haystack
// R2: needle
// R3: length of needle (2 <= len <= 32)
// R9: address to put result
TEXT indexbody<>(SB),NOSPLIT,$0-56
// main idea is to load 'sep' into separate register(s)
// to avoid repeatedly re-load it again and again
// for sebsequent substring comparisons
SUB R3, R1, R4
// R4 contains the start of last substring for comparison
ADD R0, R4, R4
ADD $1, R0, R8
CMP $8, R3
BHI greater_8
TBZ $3, R3, len_2_7
len_8:
// R5 contains 8-byte of sep
MOVD (R2), R5
loop_8:
// R6 contains substring for comparison
CMP R4, R0
BHI not_found
MOVD.P 1(R0), R6
CMP R5, R6
BNE loop_8
B found
len_2_7:
TBZ $2, R3, len_2_3
TBZ $1, R3, len_4_5
TBZ $0, R3, len_6
len_7:
// R5 and R6 contain 7-byte of sep
MOVWU (R2), R5
// 1-byte overlap with R5
MOVWU 3(R2), R6
loop_7:
CMP R4, R0
BHI not_found
MOVWU.P 1(R0), R3
CMP R5, R3
BNE loop_7
MOVWU 2(R0), R3
CMP R6, R3
BNE loop_7
B found
len_6:
// R5 and R6 contain 6-byte of sep
MOVWU (R2), R5
MOVHU 4(R2), R6
loop_6:
CMP R4, R0
BHI not_found
MOVWU.P 1(R0), R3
CMP R5, R3
BNE loop_6
MOVHU 3(R0), R3
CMP R6, R3
BNE loop_6
B found
len_4_5:
TBZ $0, R3, len_4
len_5:
// R5 and R7 contain 5-byte of sep
MOVWU (R2), R5
MOVBU 4(R2), R7
loop_5:
CMP R4, R0
BHI not_found
MOVWU.P 1(R0), R3
CMP R5, R3
BNE loop_5
MOVBU 3(R0), R3
CMP R7, R3
BNE loop_5
B found
len_4:
// R5 contains 4-byte of sep
MOVWU (R2), R5
loop_4:
CMP R4, R0
BHI not_found
MOVWU.P 1(R0), R6
CMP R5, R6
BNE loop_4
B found
len_2_3:
TBZ $0, R3, len_2
len_3:
// R6 and R7 contain 3-byte of sep
MOVHU (R2), R6
MOVBU 2(R2), R7
loop_3:
CMP R4, R0
BHI not_found
MOVHU.P 1(R0), R3
CMP R6, R3
BNE loop_3
MOVBU 1(R0), R3
CMP R7, R3
BNE loop_3
B found
len_2:
// R5 contains 2-byte of sep
MOVHU (R2), R5
loop_2:
CMP R4, R0
BHI not_found
MOVHU.P 1(R0), R6
CMP R5, R6
BNE loop_2
found:
SUB R8, R0, R0
MOVD R0, (R9)
RET
not_found:
MOVD $-1, R0
MOVD R0, (R9)
RET
greater_8:
SUB $9, R3, R11 // len(sep) - 9, offset of R0 for last 8 bytes
CMP $16, R3
BHI greater_16
len_9_16:
MOVD.P 8(R2), R5 // R5 contains the first 8-byte of sep
SUB $16, R3, R7 // len(sep) - 16, offset of R2 for last 8 bytes
MOVD (R2)(R7), R6 // R6 contains the last 8-byte of sep
loop_9_16:
// search the first 8 bytes first
CMP R4, R0
BHI not_found
MOVD.P 1(R0), R7
CMP R5, R7
BNE loop_9_16
MOVD (R0)(R11), R7
CMP R6, R7 // compare the last 8 bytes
BNE loop_9_16
B found
greater_16:
CMP $24, R3
BHI len_25_32
len_17_24:
LDP.P 16(R2), (R5, R6) // R5 and R6 contain the first 16-byte of sep
SUB $24, R3, R10 // len(sep) - 24
MOVD (R2)(R10), R7 // R7 contains the last 8-byte of sep
loop_17_24:
// search the first 16 bytes first
CMP R4, R0
BHI not_found
MOVD.P 1(R0), R10
CMP R5, R10
BNE loop_17_24
MOVD 7(R0), R10
CMP R6, R10
BNE loop_17_24
MOVD (R0)(R11), R10
CMP R7, R10 // compare the last 8 bytes
BNE loop_17_24
B found
len_25_32:
LDP.P 16(R2), (R5, R6)
MOVD.P 8(R2), R7 // R5, R6 and R7 contain the first 24-byte of sep
SUB $32, R3, R12 // len(sep) - 32
MOVD (R2)(R12), R10 // R10 contains the last 8-byte of sep
loop_25_32:
// search the first 24 bytes first
CMP R4, R0
BHI not_found
MOVD.P 1(R0), R12
CMP R5, R12
BNE loop_25_32
MOVD 7(R0), R12
CMP R6, R12
BNE loop_25_32
MOVD 15(R0), R12
CMP R7, R12
BNE loop_25_32
MOVD (R0)(R11), R12
CMP R10, R12 // compare the last 8 bytes
BNE loop_25_32
B found
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