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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 ·Compare(SB),NOSPLIT|NOFRAME,$0-56
MOVD a_base+0(FP), R2
MOVD a_len+8(FP), R0
MOVD b_base+24(FP), R3
MOVD b_len+32(FP), R1
MOVD $ret+48(FP), R7
B cmpbody<>(SB)
TEXT runtime·cmpstring(SB),NOSPLIT|NOFRAME,$0-40
MOVD a_base+0(FP), R2
MOVD a_len+8(FP), R0
MOVD b_base+16(FP), R3
MOVD b_len+24(FP), R1
MOVD $ret+32(FP), R7
B cmpbody<>(SB)
// On entry:
// R0 is the length of a
// R1 is the length of b
// R2 points to the start of a
// R3 points to the start of b
// R7 points to return value (-1/0/1 will be written here)
//
// On exit:
// R4, R5, R6, R8, R9 and R10 are clobbered
TEXT cmpbody<>(SB),NOSPLIT|NOFRAME,$0-0
CMP R2, R3
BEQ samebytes // same starting pointers; compare lengths
CMP R0, R1
CSEL LT, R1, R0, R6 // R6 is min(R0, R1)
CBZ R6, samebytes
BIC $0xf, R6, R10
CBZ R10, small // length < 16
ADD R2, R10 // end of chunk16
// length >= 16
chunk16_loop:
LDP.P 16(R2), (R4, R8)
LDP.P 16(R3), (R5, R9)
CMP R4, R5
BNE cmp
CMP R8, R9
BNE cmpnext
CMP R10, R2
BNE chunk16_loop
AND $0xf, R6, R6
CBZ R6, samebytes
SUBS $8, R6
BLT tail
// the length of tail > 8 bytes
MOVD.P 8(R2), R4
MOVD.P 8(R3), R5
CMP R4, R5
BNE cmp
SUB $8, R6
// compare last 8 bytes
tail:
MOVD (R2)(R6), R4
MOVD (R3)(R6), R5
CMP R4, R5
BEQ samebytes
cmp:
REV R4, R4
REV R5, R5
CMP R4, R5
ret:
MOVD $1, R4
CNEG HI, R4, R4
MOVD R4, (R7)
RET
small:
TBZ $3, R6, lt_8
MOVD (R2), R4
MOVD (R3), R5
CMP R4, R5
BNE cmp
SUBS $8, R6
BEQ samebytes
ADD $8, R2
ADD $8, R3
SUB $8, R6
B tail
lt_8:
TBZ $2, R6, lt_4
MOVWU (R2), R4
MOVWU (R3), R5
CMPW R4, R5
BNE cmp
SUBS $4, R6
BEQ samebytes
ADD $4, R2
ADD $4, R3
lt_4:
TBZ $1, R6, lt_2
MOVHU (R2), R4
MOVHU (R3), R5
CMPW R4, R5
BNE cmp
ADD $2, R2
ADD $2, R3
lt_2:
TBZ $0, R6, samebytes
one:
MOVBU (R2), R4
MOVBU (R3), R5
CMPW R4, R5
BNE ret
samebytes:
CMP R1, R0
CSET NE, R4
CNEG LO, R4, R4
MOVD R4, (R7)
RET
cmpnext:
REV R8, R4
REV R9, R5
CMP R4, R5
B ret
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