Diff: lwip-sys/arch/memcpy.c

Revision:

0:b2805b6888dc

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lwip-sys/arch/memcpy.c	Mon Jun 20 01:40:20 2016 +0000
@@ -0,0 +1,59 @@
+/* Copyright (C) 2013 - Adam Green (https://github.com/adamgreen)
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+#if defined(TOOLCHAIN_GCC) && defined(__thumb2__)
+
+#include <stdio.h>
+
+
+/* This is a hand written Thumb-2 assembly language version of the
+   standard C memcpy() function that can be used by the lwIP networking
+   stack to improve its performance.  It copies 4 bytes at a time and
+   unrolls the loop to perform 4 of these copies per loop iteration.
+*/
+__attribute__((naked)) void thumb2_memcpy(void* pDest, const void* pSource, size_t length)
+{
+    __asm (
+        ".syntax unified\n"
+        ".thumb\n"
+
+        // Copy 16 bytes at a time first.
+        "    lsrs    r3, r2, #4\n"
+        "    beq.n   2$\n"
+        "1$: ldr     r12, [r1], #4\n"
+        "    str     r12, [r0], #4\n"
+        "    ldr     r12, [r1], #4\n"
+        "    str     r12, [r0], #4\n"
+        "    ldr     r12, [r1], #4\n"
+        "    str     r12, [r0], #4\n"
+        "    ldr     r12, [r1], #4\n"
+        "    str     r12, [r0], #4\n"
+        "    subs    r3, #1\n"
+        "    bne     1$\n"
+
+        // Copy byte by byte for what is left.
+        "2$:\n"
+        "    ands    r3, r2, #0xf\n"
+        "    beq.n   4$\n"
+        "3$: ldrb    r12, [r1], #1\n"
+        "    strb    r12, [r0], #1\n"
+        "    subs    r3, #1\n"
+        "    bne     3$\n"
+
+        // Return to caller.
+        "4$: bx      lr\n"
+    );
+}
+
+#endif