arch/csky/abiv2/memcmp.S

Source file repositories/reference/linux-study-clean/arch/csky/abiv2/memcmp.S

File Facts

System
Linux kernel
Corpus path
arch/csky/abiv2/memcmp.S
Extension
.S
Size
2929 bytes
Lines
153
Domain
Architecture Layer
Bucket
arch/csky
Inferred role
Architecture Layer: arch/csky
Status
atlas-only

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.

#include <linux/linkage.h>
#include "sysdep.h"

ENTRY(memcmp)
	/* Test if len less than 4 bytes.  */
	mov	r3, r0
	movi	r0, 0
	mov	r12, r4
	cmplti	r2, 4
	bt	.L_compare_by_byte

	andi	r13, r0, 3
	movi	r19, 4

	/* Test if s1 is not 4 bytes aligned.  */
	bnez	r13, .L_s1_not_aligned

	LABLE_ALIGN
.L_s1_aligned:
	/* If dest is aligned, then copy.  */
	zext	r18, r2, 31, 4
	/* Test if len less than 16 bytes.  */
	bez	r18, .L_compare_by_word

.L_compare_by_4word:
	/* If aligned, load word each time.  */
	ldw	r20, (r3, 0)
	ldw	r21, (r1, 0)
	/* If s1[i] != s2[i], goto .L_byte_check.  */
	cmpne	r20, r21
	bt	.L_byte_check

	ldw	r20, (r3, 4)
	ldw	r21, (r1, 4)
	cmpne	r20, r21
	bt	.L_byte_check

	ldw	r20, (r3, 8)
	ldw	r21, (r1, 8)
	cmpne	r20, r21
	bt	.L_byte_check

	ldw	r20, (r3, 12)
	ldw	r21, (r1, 12)
	cmpne	r20, r21
	bt	.L_byte_check

	PRE_BNEZAD (r18)
	addi	a3, 16
	addi	a1, 16

	BNEZAD (r18, .L_compare_by_4word)

.L_compare_by_word:
	zext	r18, r2, 3, 2
	bez	r18, .L_compare_by_byte
.L_compare_by_word_loop:
	ldw	r20, (r3, 0)
	ldw	r21, (r1, 0)
	addi	r3, 4
	PRE_BNEZAD (r18)
	cmpne	r20, r21
	addi    r1, 4
	bt	.L_byte_check
	BNEZAD (r18, .L_compare_by_word_loop)

.L_compare_by_byte:
        zext    r18, r2, 1, 0

Annotation

Implementation Notes