BuildUDIV: If the divisor is even we can simplify the fixup of the multiplied...

BuildUDIV: If the divisor is even we can simplify the fixup of the multiplied value by introducing an early shift.

This allows us to compile "unsigned foo(unsigned x) { return x/28; }" into
	shrl	$2, %edi
	imulq	$613566757, %rdi, %rax
	shrq	$32, %rax
	ret

instead of
	movl    %edi, %eax
	imulq   $613566757, %rax, %rcx
	shrq    $32, %rcx
	subl    %ecx, %eax
	shrl    %eax
	addl    %ecx, %eax
	shrl    $4, %eax

on x86_64

llvm-svn: 127829