enhance the load/store narrowing optimization to handle a

tokenfactor in between the load/store.  This allows us to 
optimize test7 into:

_test7:                                 ## @test7
## BB#0:                                ## %entry
	movl	(%rdx), %eax
                                        ## kill: SIL<def> ESI<kill>
	movb	%sil, 5(%rdi)
	ret

instead of:

_test7:                                 ## @test7
## BB#0:                                ## %entry
	movl	4(%esp), %ecx
	movl	$-65281, %eax           ## imm = 0xFFFFFFFFFFFF00FF
	andl	4(%ecx), %eax
	movzbl	8(%esp), %edx
	shll	$8, %edx
	addl	%eax, %edx
	movl	12(%esp), %eax
	movl	(%eax), %eax
	movl	%edx, 4(%ecx)
	ret

llvm-svn: 101355