This gives the optimizer a bit more information about what the calls do.
This should result in slightly better generated code.
Code size sometimes goes up and sometimes goes down. I blame the code
size going up on the inliner which inlines more functions, because
compiling the smoke tests in the drivers repository with -opt=1 results
in a slight code size reduction in all cases.
This replaces the custom runtime.memcpy and runtime.memmove functions
with calls to LLVM builtins that should hopefully allow LLVM to better
optimize such calls. They will be lowered to regular libc memcpy/memmove
when they can't be optimized away.
When testing this change with some smoke tests, I found that many smoke
tests resulted in slightly larger binary sizes with this commit applied.
I looked into it and it appears that machine.sendUSBPacket was not
inlined before while it is with this commit applied. Additionally, when
I compared all driver smoke tests with -opt=1 I saw that many were
reduced slightly in binary size and none increased in size.
