[LLVMdev] ComputeMaskedBits Bug

Evan Cheng evan.cheng at apple.com
Wed Aug 20 16:08:19 PDT 2008

Sorry for being out of touch. Has this been fixed?


On Jul 21, 2008, at 1:09 PM, David Greene wrote:

> On Saturday 19 July 2008 23:53, Nick Lewycky wrote:
>>> That said, there are many places that don't respect the Mask.   
>>> Closer
>>> reading of the comment leads me to believe the Mask is simply a
>>> time-saving device, not a correctness-enforcing mechanism.
>> That's fine, but if you fix it that way, please audit
>> InstructionCombiner SimplifyDemandedBits, which I believe has the  
>> same bug.
> Ok.
>>> I've fixed the PHI analysis to do the min in our code and it fixes  
>>> the
>>> testcase I was working on.  Doing a min like this would also allow  
>>> us
>>> to have PHI nodes compute known zero and one bits even when there
>>> isn't a recurrence.
>> Great! Did you commit a patch for this?
> Not yet.  :(  I am waiting for some paperwork on this end.   
> Hopefully we only
> have to go through this pain once and then I can be much more  
> active.  I've
> been told it should be approved by the end of the month.
>                                                       -Dave
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