1 files changed, 95 insertions, 0 deletions
diff --git a/lib/libc/riscv/string/memset.S b/lib/libc/riscv/string/memset.S
new file mode 100644
index 000000000000..ca435dfdd5c1
--- /dev/null
+++ b/lib/libc/riscv/string/memset.S
@@ -0,0 +1,95 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2024 Strahinja Stanisic <strajabot@FreeBSD.org>
+ */
+
+#include <machine/asm.h>
+
+/*
+ * register a0 - void *dest
+ * register a1 - int c
+ * register a2 - size_t len
+ */
+ENTRY(memset)
+	andi a1, a1, 0xFF
+
+	sltiu t1, a2, 8
+	mv t0, a0
+	bnez t1, .Lend
+
+	li t1, 0x0101010101010101
+	mul a1, a1, t1
+
+	andi t1, a0, 0b111
+	andi t0, a0, ~0b111
+
+	beqz t1, .Lloop_store_64
+
+	la t2, .Lduff_start
+	slli t3, t1, 2
+	add t2, t2, t3
+	jr -4(t2)
+.Lduff_start:
+	sb a1, 1(t0)
+	sb a1, 2(t0)
+	sb a1, 3(t0)
+	sb a1, 4(t0)
+	sb a1, 5(t0)
+	sb a1, 6(t0)
+	sb a1, 7(t0)
+
+	/* a3 = a3 -(8-a) <=> a3 = a3 + (a-8) */
+	addi t1, t1, -8
+	add a2, a2, t1
+	addi t0, t0, 8
+
+.Lloop_store_64:
+	slti t1, a2, 64
+	bnez t1, .Lstore_rest
+	sd a1, 0(t0)
+	sd a1, 8(t0)
+	sd a1, 16(t0)
+	sd a1, 24(t0)
+	sd a1, 32(t0)
+	sd a1, 40(t0)
+	sd a1, 48(t0)
+	sd a1, 56(t0)
+	addi a2, a2, -64
+	addi t0, t0, 64
+	j .Lloop_store_64
+
+.Lstore_rest:
+	la t2, .Lduff_rest
+	andi t3, a2, ~0b111
+	srli t4, t3, 1
+	sub t2, t2, t4
+	jr t2
+	sd a1, 56(t0)
+	sd a1, 48(t0)
+	sd a1, 40(t0)
+	sd a1, 32(t0)
+	sd a1, 24(t0)
+	sd a1, 16(t0)
+	sd a1, 8(t0)
+	sd a1, 0(t0)
+.Lduff_rest:
+	add t0, t0, t3
+	sub a2, a2, t3
+
+.Lend:
+	slli a2, a2, 2
+	la t2, .Lduff_end
+	sub t2, t2, a2
+	jr t2
+	sb a1, 6(t0)
+	sb a1, 5(t0)
+	sb a1, 4(t0)
+	sb a1, 3(t0)
+	sb a1, 2(t0)
+	sb a1, 1(t0)
+	sb a1, (t0)
+.Lduff_end:
+	ret
+END(memset)
+