arch/nios2/lib/memset.c

Source file repositories/reference/linux-study-clean/arch/nios2/lib/memset.c

File Facts

System
Linux kernel
Corpus path
arch/nios2/lib/memset.c
Extension
.c
Size
1883 bytes
Lines
80
Domain
Architecture Layer
Bucket
arch/nios2
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

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

#include <linux/types.h>
#include <linux/string.h>

void *memset(void *s, int c, size_t count)
{
	int destptr, charcnt, dwordcnt, fill8reg, wrkrega;

	if (!count)
		return s;

	c &= 0xFF;

	if (count <= 8) {
		char *xs = (char *) s;

		while (count--)
			*xs++ = c;
		return s;
	}

	__asm__ __volatile__ (
		/* fill8 %3, %5 (c & 0xff) */
		"	slli	%4, %5, 8\n"
		"	or	%4, %4, %5\n"
		"	slli    %3, %4, 16\n"
		"	or	%3, %3, %4\n"
		/* Word-align %0 (s) if necessary */
		"	andi	%4, %0, 0x01\n"
		"	beq	%4, zero, 1f\n"
		"	addi	%1, %1, -1\n"
		"	stb	%3, 0(%0)\n"
		"	addi	%0, %0, 1\n"
		"1:	mov	%2, %1\n"
		/* Dword-align %0 (s) if necessary */
		"	andi	%4, %0, 0x02\n"
		"	beq	%4, zero, 2f\n"
		"	addi	%1, %1, -2\n"
		"	sth	%3, 0(%0)\n"
		"	addi	%0, %0, 2\n"
		"	mov	%2, %1\n"
		/* %1 and %2 are how many more bytes to set */
		"2:	srli	%2, %2, 2\n"
		/* %2 is how many dwords to set */
		"3:	stw	%3, 0(%0)\n"
		"	addi	%0, %0, 4\n"
		"	addi    %2, %2, -1\n"
		"	bne	%2, zero, 3b\n"
		/* store residual word and/or byte if necessary */
		"	andi	%4, %1, 0x02\n"
		"	beq	%4, zero, 4f\n"
		"	sth	%3, 0(%0)\n"
		"	addi	%0, %0, 2\n"
		/* store residual byte if necessary */
		"4:	andi	%4, %1, 0x01\n"
		"	beq	%4, zero, 5f\n"
		"	stb	%3, 0(%0)\n"
		"5:\n"
		: "=r" (destptr),	/* %0  Output */
		  "=r" (charcnt),	/* %1  Output */
		  "=r" (dwordcnt),	/* %2  Output */
		  "=r" (fill8reg),	/* %3  Output */
		  "=&r" (wrkrega)	/* %4  Output only */
		: "r" (c),		/* %5  Input */
		  "0" (s),		/* %0  Input/Output */
		  "1" (count)		/* %1  Input/Output */
		: "memory"		/* clobbered */
	);

	return s;
}

Annotation

Implementation Notes