Make some existing optimizations that would only trigger on scalars

Make some existing optimizations that would only trigger on scalars
also apply to vectors.  This allows us to compile this:

#include <emmintrin.h>
__m128i a(__m128 a, __m128 b) { return a==a & b==b; }
__m128i b(__m128 a, __m128 b) { return a!=a | b!=b; }

to:

_a:
	cmpordps	%xmm1, %xmm0
	ret
_b:
	cmpunordps	%xmm1, %xmm0
	ret

with clang instead of to a ton of horrible code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76863 91177308-0d34-0410-b5e6-96231b3b80d8