github.com/sandwichdev/go-internals@v0.0.0-20210605002614-12311ac6b2c5/bytealg/count_arm.s (about)

     1  // Copyright 2019 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  #include "go_asm.h"
     6  #include "textflag.h"
     7  
     8  TEXT ·Count(SB),NOSPLIT,$0-20
     9  	MOVW	b_base+0(FP), R0
    10  	MOVW	b_len+4(FP), R1
    11  	MOVBU	c+12(FP), R2
    12  	MOVW	$ret+16(FP), R7
    13  	B	countbytebody<>(SB)
    14  
    15  TEXT ·CountString(SB),NOSPLIT,$0-16
    16  	MOVW	s_base+0(FP), R0
    17  	MOVW	s_len+4(FP), R1
    18  	MOVBU	c+8(FP), R2
    19  	MOVW	$ret+12(FP), R7
    20  	B	countbytebody<>(SB)
    21  
    22  // Input:
    23  // R0: data
    24  // R1: data length
    25  // R2: byte to find
    26  // R7: address to put result
    27  //
    28  // On exit:
    29  // R4 and R8 are clobbered
    30  TEXT countbytebody<>(SB),NOSPLIT,$0
    31  	MOVW	$0, R8	// R8 = count of byte to search
    32  	CMP	$0, R1
    33  	B.EQ	done	// short path to handle 0-byte case
    34  	ADD	R0, R1	// R1 is the end of the range
    35  byte_loop:
    36  	MOVBU.P	1(R0), R4
    37  	CMP	R4, R2
    38  	ADD.EQ	$1, R8
    39  	CMP	R0, R1
    40  	B.NE	byte_loop
    41  done:
    42  	MOVW	R8, (R7)
    43  	RET