simonjhall / copies-and-fills Goto Github PK

Memset uses:

stmia r0!, {r1, r4, r5, r6}
stmia r0!, {r7, r8, r9, r10}

to store the data out, where as mempcy uses:

    str r4, [r0], #4
str r5, [r0], #4
str r6, [r0], #4
str r7, [r0], #4
str r8, [r0], #4
str r9, [r0], #4
str r10, [r0], #4

It appears to me they do the same thing, but one in less instructons - no idea of the timings, but smaller code should be worth it even if the timing is equal. Not sure if there is a load-multiple that could replace the loads as well. Also there appear to be just 7 load/stores in that area?

Hmmm...just noticed this is a bit of code on the wrong side of a #if 1 - I'll get back in my cave.

I'm not sure if this has been addressed yet, but I know raspbian includes this library and loads it by default. When using qemu to emulate a raspbian environment, you have to comment out the line in /etc/ld.so.preload that loads libcofi_rpi.so (any tutorial for using qemu-user with raspbian will tell you to do this).

Commenting out a line is easy enough, except that you have to remember to uncomment it when you're done working in the emulated environment.

Is there a way make this library qemu-safe?

void memcpy(void *dest,
const void *source,
size_t source);

thirds argument should be called 'count' or something I guess.