[llvm-commits] [llvm] r128333 - /llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp

[Bill Wendling]

On Mar 26, 2011, at 8:52 AM, Frits van Bommel wrote:

> On Sat, Mar 26, 2011 at 4:39 PM, Dan Gohman <gohman at apple.com> wrote:
>> On Mar 26, 2011, at 2:32 AM, Bill Wendling wrote:
>>> Simplification noticed by Frits.
>>> 
>>> Modified:
>>>    llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp
> 
>>> -  if ((EarlierOff == LaterOff && Earlier.Size <= Later.Size) ||
>>> -      (EarlierOff > LaterOff &&
>>> -       EarlierOff + Earlier.Size <= LaterOff + Later.Size))
>>> +  if (EarlierOff >= LaterOff &&
>>> +      EarlierOff + Earlier.Size <= LaterOff + Later.Size)
>>>     return true;
>> 
>> I don't have time to fully investigate, but the testcase passes without the fix,
> 
> What testcase? This commit doesn't have a testcase (and doesn't need
> one, given the next point).
> 
>> and the new code is now equivalent by De Morgan's law to the old code.
> 
> Hint: the commit message called it a "simplification" because it *is*
> equivalent (but simpler) code.
> 
> I'm not sure where you're getting De Morgan's law from though, since
> there's no negation anywhere...
> (The only De Morgan's laws I know about are these:
> <http://en.wikipedia.org/wiki/De_Morgan%27s_laws>)

I think he means from what it originally was. The reason I'm messing with this code is because of PR9561. What I did is a De Morgan's change from the old code. But I disagree that the testcase passed before the previous change:

	http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20110321/118574.html

At least it didn't pass for me. :)

-bw