1 files changed, 64 insertions, 0 deletions
diff --git a/lib/libc/aarch64/memset.S b/lib/libc/aarch64/memset.S
new file mode 100644
index 0000000..0543704
--- /dev/null
+++ b/lib/libc/aarch64/memset.S
@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2020, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <asm_macros.S>
+
+	.global	memset
+
+/* -----------------------------------------------------------------------
+ * void *memset(void *dst, int val, size_t count)
+ *
+ * Copy the value of 'val' (converted to an unsigned char) into
+ * each of the first 'count' characters of the object pointed to by 'dst'.
+ *
+ * Returns the value of 'dst'.
+ * -----------------------------------------------------------------------
+ */
+func memset
+	cbz	x2, exit		/* exit if 'count' = 0 */
+	mov	x3, x0			/* keep x0 */
+	tst	x0, #7
+	b.eq	aligned			/* 8-bytes aligned */
+
+	/* Unaligned 'dst' */
+unaligned:
+	strb	w1, [x3], #1
+	subs	x2, x2, #1
+	b.eq	exit			/* exit if 0 */
+	tst	x3, #7
+	b.ne	unaligned		/* continue while unaligned */
+
+	/* 8-bytes aligned */
+aligned:cbz	x1, x1_zero
+	bfi	w1, w1, #8, #8		/* propagate 'val' */
+	bfi	w1, w1, #16, #16
+	bfi	x1, x1, #32, #32
+
+x1_zero:ands	x4, x2, #~0x3f
+	b.eq	less_64
+
+write_64:
+	.rept	4
+	stp	x1, x1, [x3], #16	/* write 64 bytes in a loop */
+	.endr
+	subs	x4, x4, #64
+	b.ne	write_64
+less_64:tbz	w2, #5, less_32		/* < 32 bytes */
+	stp	x1, x1, [x3], #16	/* write 32 bytes */
+	stp	x1, x1, [x3], #16
+less_32:tbz	w2, #4, less_16		/* < 16 bytes */
+	stp	x1, x1, [x3], #16	/* write 16 bytes */
+less_16:tbz	w2, #3, less_8		/* < 8 bytes */
+	str	x1, [x3], #8		/* write 8 bytes */
+less_8:	tbz	w2, #2, less_4		/* < 4 bytes */
+	str	w1, [x3], #4		/* write 4 bytes */
+less_4:	tbz	w2, #1, less_2		/* < 2 bytes */
+	strh	w1, [x3], #2		/* write 2 bytes */
+less_2:	tbz	w2, #0, exit
+	strb	w1, [x3]		/* write 1 byte */
+exit:	ret
+
+endfunc	memset