teach the x86 address matching stuff to handle

(shl (or x,c), 3) the same as (shl (add x, c), 3)
when x doesn't have any bits from c set.

This finishes off PR1135.  Before we compiled the block to:
to:

LBB0_3:                                 ## %bb
	cmpb	$4, %dl
	sete	%dl
	addb	%dl, %cl
	movb	%cl, %dl
	shlb	$2, %dl
	addb	%r8b, %dl
	shlb	$2, %dl
	movzbl	%dl, %edx
	movl	%esi, (%rdi,%rdx,4)
	leaq	2(%rdx), %r9
	movl	%esi, (%rdi,%r9,4)
	leaq	1(%rdx), %r9
	movl	%esi, (%rdi,%r9,4)
	addq	$3, %rdx
	movl	%esi, (%rdi,%rdx,4)
	incb	%r8b
	decb	%al
	movb	%r8b, %dl
	jne	LBB0_1

Now we produce:

LBB0_3:                                 ## %bb
	cmpb	$4, %dl
	sete	%dl
	addb	%dl, %cl
	movb	%cl, %dl
	shlb	$2, %dl
	addb	%r8b, %dl
	shlb	$2, %dl
	movzbl	%dl, %edx
	movl	%esi, (%rdi,%rdx,4)
	movl	%esi, 8(%rdi,%rdx,4)
	movl	%esi, 4(%rdi,%rdx,4)
	movl	%esi, 12(%rdi,%rdx,4)
	incb	%r8b
	decb	%al
	movb	%r8b, %dl
	jne	LBB0_1

llvm-svn: 101958