[polly] r261474 - [FIX] Compare SCEVs not values during SCEV expansion

[Johannes Doerfert via llvm-commits]

On 02/21, Tobias Grosser wrote:
> On 02/21/2016 07:16 PM, Johannes Doerfert wrote:
> >>On 02/21/2016 05:36 PM, Johannes Doerfert via llvm-commits wrote:
> >>>Author: jdoerfert
> >>>Date: Sun Feb 21 10:36:00 2016
> >>>New Revision: 261474
> >>>
> >>>URL: http://llvm.org/viewvc/llvm-project?rev=261474&view=rev
> >>>Log:
> >>>[FIX] Compare SCEVs not values during SCEV expansion
> >>>
> >>>   This fixes a compile time bug in SPEC2006 403.gcc, namely an endless
> >>>   recursion in the ScopExpander::visitUnknown function.
> >>
> >>A test case would be good. Was there  a specific reason you could not add a
> >>test case?
> >I tried but could not generate one. Only when I run it with clang I
> >triggered the problem. Tried to extract the module as Polly sees it but
> >it didn't help.
> 
> How did you extract the code from clang?
I dumped the Module in ScopInfo for the original command line. But I
still could not reproduce the behaviour afterwards (opt -O3 -polly on
the module).

> The following commands should be equivalent to 'clang -O3 -mllvm -polly':
> 
> 	clang -O3 -mllvm -disable-llvm-optzns -S -emit-llvm -o out.ll
> 	opt -O3 -polly
> 
> Not that extracting test cases with 'clang -O0 -S -emit-llvm' does not give
> the same results. When -O0 is specified clang e.g. does not emit
> type based alias analysis metadata which could prevent Polly from optimizing
> code that it would have optimized otherwise.
> 
> Best,
> Tobias

-- 

Johannes Doerfert
Researcher / PhD Student

Compiler Design Lab (Prof. Hack)
Saarland University, Computer Science
Building E1.3, Room 4.31

Tel. +49 (0)681 302-57521 : doerfert at cs.uni-saarland.de
Fax. +49 (0)681 302-3065  : http://www.cdl.uni-saarland.de/people/doerfert
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