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// Copyright 2022 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<ABIInternal>(SB),NOSPLIT,$0-56
// R4 = a_base
// R5 = a_len
// R6 = a_cap (unused)
// R7 = b_base (want in R6)
// R8 = b_len (want in R7)
// R9 = b_cap (unused)
MOVV R7, R6
MOVV R8, R7
JMP cmpbody<>(SB)
TEXT runtime·cmpstring<ABIInternal>(SB),NOSPLIT,$0-40
// R4 = a_base
// R5 = a_len
// R6 = b_base
// R7 = b_len
JMP cmpbody<>(SB)
// On entry:
// R5 length of a
// R7 length of b
// R4 points to the start of a
// R6 points to the start of b
// R13 points to the return value (-1/0/1)
TEXT cmpbody<>(SB),NOSPLIT|NOFRAME,$0
BEQ R4, R6, samebytes // same start of a and b
SGTU R5, R7, R9
BNE R0, R9, r2_lt_r1
MOVV R5, R14
JMP entry
r2_lt_r1:
MOVV R7, R14 // R14 is min(R4, R5)
entry:
ADDV R4, R14, R12 // R6 start of a, R14 end of a
BEQ R4, R12, samebytes // length is 0
SRLV $4, R14 // R14 is number of chunks
BEQ R0, R14, byte_loop
// make sure both a and b are aligned.
OR R4, R6, R15
AND $7, R15
BNE R0, R15, byte_loop
PCALIGN $16
chunk16_loop:
BEQ R0, R14, byte_loop
MOVV (R4), R8
MOVV (R6), R9
BNE R8, R9, byte_loop
MOVV 8(R4), R16
MOVV 8(R6), R17
ADDV $16, R4
ADDV $16, R6
SUBVU $1, R14
BEQ R16, R17, chunk16_loop
SUBV $8, R4
SUBV $8, R6
byte_loop:
BEQ R4, R12, samebytes
MOVBU (R4), R8
ADDVU $1, R4
MOVBU (R6), R9
ADDVU $1, R6
BEQ R8, R9, byte_loop
byte_cmp:
SGTU R8, R9, R4 // R12 = 1 if (R8 > R9)
BNE R0, R4, ret
MOVV $-1, R4
JMP ret
samebytes:
SGTU R5, R7, R8
SGTU R7, R5, R9
SUBV R9, R8, R4
ret:
RET
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