diff options
Diffstat (limited to 'src/bytes/bytes_arm64.s')
| -rw-r--r-- | src/bytes/bytes_arm64.s | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/src/bytes/bytes_arm64.s b/src/bytes/bytes_arm64.s new file mode 100644 index 0000000000..5e229d772b --- /dev/null +++ b/src/bytes/bytes_arm64.s @@ -0,0 +1,74 @@ +// Copyright 2017 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 "textflag.h" + +// countByte(s []byte, c byte) int +TEXT bytes·countByte(SB),NOSPLIT,$0-40 + MOVD s_base+0(FP), R0 + MOVD s_len+8(FP), R2 + MOVBU c+24(FP), R1 + // 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, ret+32(FP) + RET |