Re: A bug in vrp_meet?

[Qing Zhao <qing dot zhao at oracle dot com>]

> On Mar 1, 2019, at 1:25 PM, Richard Biener <richard.guenther@gmail.com> wrote:
> 
> On March 1, 2019 6:49:20 PM GMT+01:00, Qing Zhao <qing.zhao@oracle.com <mailto:qing.zhao@oracle.com>> wrote:
>> Jeff,
>> 
>> thanks a lot for the reply.
>> 
>> this is really helpful.
>> 
>> I double checked the dumped intermediate file for pass “dom3", and
>> located the following for _152:
>> 
>> ****BEFORE the pass “dom3”, there is no _152, the corresponding Block
>> looks like:
>> 
>> <bb 4> [local count: 12992277]:
>> _98 = (int) ufcMSR_52(D);
>> k_105 = (sword) ufcMSR_52(D);
>> i_49 = _98 > 0 ? k_105 : 0;
>> 
>> ***During the pass “doms”,  _152 is generated as following:
>> 
>> Optimizing block #4
>> ….
>> Visiting statement:
>> i_49 = _98 > 0 ? k_105 : 0;
>> Meeting
>> [0, 65535]
>> and
>> [0, 0]
>> to
>> [0, 65535]
>> Intersecting
>> [0, 65535]
>> and
>> [0, 65535]
>> to
>> [0, 65535]
>> Optimizing statement i_49 = _98 > 0 ? k_105 : 0;
>> Replaced 'k_105' with variable '_98'
>> gimple_simplified to _152 = MAX_EXPR <_98, 0>;
>> i_49 = _152;
>> Folded to: i_49 = _152;
>> LKUP STMT i_49 = _152
>> ==== ASGN i_49 = _152
>> 
>> then bb 4 becomes:
>> 
>> <bb 4> [local count: 12992277]:
>> _98 = (int) ufcMSR_52(D);
>> k_105 = _98;
>> _152 = MAX_EXPR <_98, 0>;
>> i_49 = _152;
>> 
>> and all the i_49 are replaced with _152. 
>> 
>> However, the value range info for _152 doesnot reflect the one for
>> i_49, it keeps as UNDEFINED. 
>> 
>> is this the root problem?  
> 
> It looks like DOM fails to visit stmts generated by simplification. Can you open a bug report with a testcase?

The problem is, It took me quite some time in order to come up with a small and independent testcase for this problem,
a little bit change made the error disappear.  

do you have any suggestion on this?  or can you give me some hint on how to fix this in DOM?  then I can try the fix on my side?

Thanks a lot.

Qing


> 
> Richard. 
>