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-rw-r--r--lib/libc/aarch64/memset.S64
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