blob: a791c7396a8d927d8fc1e2c02c5d9e2df37ff143 [file] [log] [blame]
// 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,$0-20
MOVL b_base+0(FP), SI
MOVL b_len+4(FP), BX
MOVB c+12(FP), AL
CALL indexbytebody<>(SB)
MOVL AX, ret+16(FP)
RET
TEXT ·IndexByteString(SB),NOSPLIT,$0-20
MOVL s_base+0(FP), SI
MOVL s_len+4(FP), BX
MOVB c+8(FP), AL
CALL indexbytebody<>(SB)
MOVL AX, ret+16(FP)
RET
TEXT bytes·IndexByte(SB),NOSPLIT,$0-20
FUNCDATA $0, ·IndexByte·args_stackmap(SB)
MOVL b_base+0(FP), SI
MOVL b_len+4(FP), BX
MOVB c+12(FP), AL
CALL indexbytebody<>(SB)
MOVL AX, ret+16(FP)
RET
TEXT strings·IndexByte(SB),NOSPLIT,$0-20
FUNCDATA $0, ·IndexByteString·args_stackmap(SB)
MOVL s_base+0(FP), SI
MOVL s_len+4(FP), BX
MOVB c+8(FP), AL
CALL indexbytebody<>(SB)
MOVL AX, ret+16(FP)
RET
// input:
// SI: data
// BX: data len
// AL: byte sought
// output:
// AX
TEXT indexbytebody<>(SB),NOSPLIT,$0
MOVL SI, DI
CMPL BX, $16
JLT small
// round up to first 16-byte boundary
TESTL $15, SI
JZ aligned
MOVL SI, CX
ANDL $~15, CX
ADDL $16, CX
// search the beginning
SUBL SI, CX
REPN; SCASB
JZ success
// DI is 16-byte aligned; get ready to search using SSE instructions
aligned:
// round down to last 16-byte boundary
MOVL BX, R11
ADDL SI, R11
ANDL $~15, R11
// shuffle X0 around so that each byte contains c
MOVD AX, X0
PUNPCKLBW X0, X0
PUNPCKLBW X0, X0
PSHUFL $0, X0, X0
JMP condition
sse:
// move the next 16-byte chunk of the buffer into X1
MOVO (DI), X1
// compare bytes in X0 to X1
PCMPEQB X0, X1
// take the top bit of each byte in X1 and put the result in DX
PMOVMSKB X1, DX
TESTL DX, DX
JNZ ssesuccess
ADDL $16, DI
condition:
CMPL DI, R11
JNE sse
// search the end
MOVL SI, CX
ADDL BX, CX
SUBL R11, CX
// if CX == 0, the zero flag will be set and we'll end up
// returning a false success
JZ failure
REPN; SCASB
JZ success
failure:
MOVL $-1, AX
RET
// handle for lengths < 16
small:
MOVL BX, CX
REPN; SCASB
JZ success
MOVL $-1, AX
RET
// we've found the chunk containing the byte
// now just figure out which specific byte it is
ssesuccess:
// get the index of the least significant set bit
BSFW DX, DX
SUBL SI, DI
ADDL DI, DX
MOVL DX, AX
RET
success:
SUBL SI, DI
SUBL $1, DI
MOVL DI, AX
RET