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-rw-r--r--src/internal/bytealg/count_arm.s43
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diff --git a/src/internal/bytealg/count_arm.s b/src/internal/bytealg/count_arm.s
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+// Copyright 2019 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,$0-20
+ MOVW b_base+0(FP), R0
+ MOVW b_len+4(FP), R1
+ MOVBU c+12(FP), R2
+ MOVW $ret+16(FP), R7
+ B countbytebody<>(SB)
+
+TEXT ·CountString(SB),NOSPLIT,$0-16
+ MOVW s_base+0(FP), R0
+ MOVW s_len+4(FP), R1
+ MOVBU c+8(FP), R2
+ MOVW $ret+12(FP), R7
+ B countbytebody<>(SB)
+
+// Input:
+// R0: data
+// R1: data length
+// R2: byte to find
+// R7: address to put result
+//
+// On exit:
+// R4 and R8 are clobbered
+TEXT countbytebody<>(SB),NOSPLIT,$0
+ MOVW $0, R8 // R8 = count of byte to search
+ CMP $0, R1
+ B.EQ done // short path to handle 0-byte case
+ ADD R0, R1 // R1 is the end of the range
+byte_loop:
+ MOVBU.P 1(R0), R4
+ CMP R4, R2
+ ADD.EQ $1, R8
+ CMP R0, R1
+ B.NE byte_loop
+done:
+ MOVW R8, (R7)
+ RET