Use the RHS length instead of the LHS length. They are both the same,

Use the RHS length instead of the LHS length.  They are both the same,
but this ends up compiling code like this:

int foo(const StringRef &R) {
  return R == "food";
}

to use a constant sized memcmp instead of a variable memcmp.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@77160 91177308-0d34-0410-b5e6-96231b3b80d8