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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 ·Count(SB),NOSPLIT,$0-40
MOVD b_base+0(FP), R0
MOVD b_len+8(FP), R2
MOVBU c+24(FP), R1
MOVD $ret+32(FP), R8
B countbytebody<>(SB)
TEXT ·CountString(SB),NOSPLIT,$0-32
MOVD s_base+0(FP), R0
MOVD s_len+8(FP), R2
MOVBU c+16(FP), R1
MOVD $ret+24(FP), R8
B countbytebody<>(SB)
// input:
// R0: data
// R2: data len
// R1: byte to find
// R8: address to put result
TEXT countbytebody<>(SB),NOSPLIT,$0
// R11 = count of byte to search
MOVD $0, R11
// short path to handle 0-byte case
CBZ R2, done
CMP $0x20, R2
// jump directly to tail if length < 32
BLO tail
ANDS $0x1f, R0, R9
BEQ chunk
// Work with not 32-byte aligned head
BIC $0x1f, R0, R3
ADD $0x20, R3
head_loop:
MOVBU.P 1(R0), R5
CMP R5, R1
CINC EQ, R11, R11
SUB $1, R2, R2
CMP R0, R3
BNE head_loop
// Work with 32-byte aligned chunks
chunk:
BIC $0x1f, R2, R9
// The first chunk can also be the last
CBZ R9, tail
// R3 = end of 32-byte chunks
ADD R0, R9, R3
MOVD $1, R5
VMOV R5, V5.B16
// R2 = length of tail
SUB R9, R2, R2
// Duplicate R1 (byte to search) to 16 1-byte elements of V0
VMOV R1, V0.B16
// Clear the low 64-bit element of V7 and V8
VEOR V7.B8, V7.B8, V7.B8
VEOR V8.B8, V8.B8, V8.B8
// Count the target byte in 32-byte chunk
chunk_loop:
VLD1.P (R0), [V1.B16, V2.B16]
CMP R0, R3
VCMEQ V0.B16, V1.B16, V3.B16
VCMEQ V0.B16, V2.B16, V4.B16
// Clear the higher 7 bits
VAND V5.B16, V3.B16, V3.B16
VAND V5.B16, V4.B16, V4.B16
// Count lanes match the requested byte
VADDP V4.B16, V3.B16, V6.B16 // 32B->16B
VUADDLV V6.B16, V7
// Accumulate the count in low 64-bit element of V8 when inside the loop
VADD V7, V8
BNE chunk_loop
VMOV V8.D[0], R6
ADD R6, R11, R11
CBZ R2, done
tail:
// Work with tail shorter than 32 bytes
MOVBU.P 1(R0), R5
SUB $1, R2, R2
CMP R5, R1
CINC EQ, R11, R11
CBNZ R2, tail
done:
MOVD R11, (R8)
RET
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