Implement a readme entry, compiling

Implement a readme entry, compiling
#include <xmmintrin.h>
__m128i doload64(short x) {return _mm_set_epi16(0,0,0,0,0,0,0,1);}

into:
	movl	$1, %eax
	movd	%eax, %xmm0
	ret

instead of a constant pool load.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48063 91177308-0d34-0410-b5e6-96231b3b80d8