Edits a hard-coded string in an unrolled loop
I was told in the IRC channel that the non optimized LLVM code I was getting of
the attached C++ code was related to this issue.
It becomes optimized when the string 's' becomes small, like "this".
example with poor memcpy optimization
In the last line
return r + x.A;
the value of x.A is zero, but LLVM doesn't understand this.
Presumably this is because it thinks memcpy has modified x,
even though it copies from x and not to it.