[LLVMdev] Simplifying selects + arm stuff

[Evan Cheng]

On Nov 12, 2010, at 11:53 AM, Chris Lattner wrote:

> 
> On Nov 12, 2010, at 11:46 AM, Evan Cheng wrote:
> 
>> 
>> This should be
>> 
>>       cmp     r0, r1
>>       movlt.w r2, #-1     @ or mvnlt r2, #0
>>       and.w   r0, r2, r3
>>       bx      lr
>> 
>> which we gets right in Thumb2 mode (I need to check why it's not matching in ARM mode). How can we use a conditional and here? The result is either (y & -1) or (y & x), the "and" is not conditional.
> 
> y&-1 == y.  There is no need to materialize -1 as a constant.

Yes, *face palm*. That will require target specific dag combine.

Evan

> 
> -Chris