[PATCH] PR17473: Disallow LSR to perform non-invertible normalization

[Andrew Trick]

On Mar 10, 2014, at 5:00 PM, Eric Christopher <echristo at gmail.com> wrote:

>> As we discussed, once you have finished running the test-suite with a check
>> to find out if any important cases are no longer normalized as expected,
>> then I think you can commit. I know you've already verified performance, so
>> this is just an extra sanity check.
>> 
> 
> Any interesting results?

No performance changes, just fixing PR17473.

-Andy

> 
> -eric
> 
>> Thanks.
>> 
>> -Andy
>> 
>> 
>> Thanks,
>> Michael
>> 
>> Thanks,
>> Arnold
>> 
>> On Mar 10, 2014, at 2:56 PM, Michael Zolotukhin <mzolotukhin at apple.com>
>> wrote:
>> 
>> Hi,
>> 
>> This is a fix for PR17473. The issue is that LSR performs normalization of
>> detected IV users and sometimes wants to denormalize it back hoping to get
>> the original expression. But normalization isn't always invertible, and the
>> new expression might be not equivalent to the original one. In the test
>> case, we were losing sign-extension in such transformation. The patch simply
>> adds a check, if the transformation is invertible.
>> 
>> <pr17473.patch>
>> 
>> Ok for trunk?
>> 
>> Thanks,
>> Michael
>> 
>> 
>> 
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