1 files changed, 38 insertions, 0 deletions
diff --git a/rgo/src/memfill.S b/rgo/src/memfill.S
new file mode 100644
index 0000000..3c4fb1f
--- /dev/null
+++ b/rgo/src/memfill.S
@@ -0,0 +1,38 @@
+/*
+ Copyright 2022 Gabriel Jensen
+
+ This file is part of rgo.
+
+ rgo is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
+
+ rgo is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License along with rgo. If not, see <https://www.gnu.org/licenses/>. 
+*/
+
+#include <rgo.h>
+
+.global rgo_memfill
+
+rgo_memfill:
+#if defined(__x86_64__)
+ /*
+ rdi: void const * ptr
+ rsi: size_t num
+ dl: int_least8_t val
+ */
+ /* We don't need to preserve any of the registers we use according to the ABI. */
+ /* rcx: Address of the current element. */
+ movq %rdi,%rcx
+ /* r8: Address of the last element. */
+ movq %rdi,%r8
+ addq %rsi,%r8
+.loop:
+ cmpq %r8,%rcx
+ je .done /* Exit loop if we have reached the final element. */
+ movb %dl,(%rcx)
+ incq %rcx /* Continue to next element. */
+ jmp .loop
+.done:
+ ret
+#endif