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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 ·IndexByte(SB),NOSPLIT|NOFRAME,$0-40
MOVD b_base+0(FP), R3// b_base => R3
MOVD b_len+8(FP), R4 // b_len => R4
MOVBZ c+24(FP), R5 // c => R5
MOVD $ret+32(FP), R2 // &ret => R9
BR indexbytebody<>(SB)
TEXT ·IndexByteString(SB),NOSPLIT|NOFRAME,$0-32
MOVD s_base+0(FP), R3// s_base => R3
MOVD s_len+8(FP), R4 // s_len => R4
MOVBZ c+16(FP), R5 // c => R5
MOVD $ret+24(FP), R2 // &ret => R9
BR indexbytebody<>(SB)
// input:
// R3: s
// R4: s_len
// R5: c -- byte sought
// R2: &ret -- address to put index into
TEXT indexbytebody<>(SB),NOSPLIT|NOFRAME,$0
CMPBEQ R4, $0, notfound
MOVD R3, R6 // store base for later
ADD R3, R4, R8 // the address after the end of the string
//if the length is small, use loop; otherwise, use vector or srst search
CMPBGE R4, $16, large
residual:
CMPBEQ R3, R8, notfound
MOVBZ 0(R3), R7
LA 1(R3), R3
CMPBNE R7, R5, residual
found:
SUB R6, R3
SUB $1, R3
MOVD R3, 0(R2)
RET
notfound:
MOVD $-1, 0(R2)
RET
large:
MOVBZ internal∕cpu·S390X+const_offsetS390xHasVX(SB), R1
CMPBNE R1, $0, vectorimpl
srstimpl: // no vector facility
MOVBZ R5, R0 // c needs to be in R0, leave until last minute as currently R0 is expected to be 0
srstloop:
WORD $0xB25E0083 // srst %r8, %r3 (search the range [R3, R8))
BVS srstloop // interrupted - continue
BGT notfoundr0
foundr0:
XOR R0, R0 // reset R0
SUB R6, R8 // remove base
MOVD R8, 0(R2)
RET
notfoundr0:
XOR R0, R0 // reset R0
MOVD $-1, 0(R2)
RET
vectorimpl:
//if the address is not 16byte aligned, use loop for the header
MOVD R3, R8
AND $15, R8
CMPBGT R8, $0, notaligned
aligned:
ADD R6, R4, R8
MOVD R8, R7
AND $-16, R7
// replicate c across V17
VLVGB $0, R5, V19
VREPB $0, V19, V17
vectorloop:
CMPBGE R3, R7, residual
VL 0(R3), V16 // load string to be searched into V16
ADD $16, R3
VFEEBS V16, V17, V18 // search V17 in V16 and set conditional code accordingly
BVS vectorloop
// when vector search found c in the string
VLGVB $7, V18, R7 // load 7th element of V18 containing index into R7
SUB $16, R3
SUB R6, R3
ADD R3, R7
MOVD R7, 0(R2)
RET
notaligned:
MOVD R3, R8
AND $-16, R8
ADD $16, R8
notalignedloop:
CMPBEQ R3, R8, aligned
MOVBZ 0(R3), R7
LA 1(R3), R3
CMPBNE R7, R5, notalignedloop
BR found
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