Add mempcpy implementation

A GNU extension that returns dst + size instead of dst. It's a nice
shortcut when copying strings with a known size or back-to-back blocks
and you have to do it often.

May of course be called directly or alternately through
__builtin_mempcpy in some compiler versions.

For ASM on native targets, it is implemented as an alternate entrypoint
to memcpy which adds minimal code and overhead.

Change-Id: I4cbb3483f6df3c1007247fe0a95fd7078737462b

1 files changed, 8 insertions, 0 deletions

diff --git a/firmware/asm/sh/memcpy.S b/firmware/asm/sh/memcpy.S
index 59c5801ac0..3d623c48cd 100644
--- a/firmware/asm/sh/memcpy.S
+++ b/firmware/asm/sh/memcpy.S
@@ -24,8 +24,10 @@
 
     .align      2
     .global     _memcpy
+    .global     _mempcpy
     .global     ___memcpy_fwd_entry
     .type       _memcpy,@function
+    .type       _mempcpy,@function
 
 /* Copies <length> bytes of data in memory from <source> to <dest>
  * This version is optimized for speed
@@ -51,6 +53,10 @@
  * The instruction order is devised in a way to utilize the pipelining
  * of the SH1 to the max. The routine also tries to utilize fast page mode.
  */
+_mempcpy:
+    mov     r4,r7       /* store dest + length for returning */
+    bra     ___memcpy_fwd_entry
+     add    r6,r7
 
 _memcpy:
     mov     r4,r7       /* store dest for returning */
@@ -217,3 +223,5 @@ ___memcpy_fwd_entry:
     mov     r7,r0       /* return dest start address */
 .end:
     .size   _memcpy,.end-_memcpy
+    .size   _mempcpy,.end-_mempcpy
+