[llvm-commits] [polly] r152913 - in /polly/trunk: lib/Support/SCEVValidator.cpp test/ScopInfo/2012-03-16-Crash-because-of-unsigned-in-scev.ll

[Sebastian Pop]

Tobias Grosser wrote:
> On 09/24/2013 06:41 PM, Sebastian Pop wrote:
> >Hi Tobi,
> >
> >it looks like this change breaks in code generation with:
> >"Use still stuck around after Def is destroyed"
> >
> >    class ValidatorResult visitSMaxExpr(const SCEVSMaxExpr *Expr) {
> >-    ValidatorResult Return(SCEVType::INT);
> >+    ValidatorResult Return(SCEVType::INT, Expr);
> >
> >     for (int i = 0, e = Expr->getNumOperands(); i < e; ++i) {
> >       ValidatorResult Op = visit(Expr->getOperand(i));
> >
> >       if (!Op.isValid())
> >         return Op;
> >
> >       Return.merge(Op);
> >     }
> >
> >     return Return;
> >   }
> >
> >The problem seems to be that we are adding the full original
> >SMax expression to the result
> >and that references SSA names of the original scop.
> >
> >Ok to revert this change?
> 
> This change is over a year old. It fixes an actual problem and the
> change itself does not loop obviously wrong. So reverting it is
> nothing I feel comfortable with.
> 
> If we do not update SSA names correctly, it would be interesting to
> understand why. For this an actual test case would help. For me,
> the following commands do not show any issues:
> 
> $ polly-opt
> test/ScopInfo/2012-03-16-Crash-because-of-unsigned-in-scev.ll
> -polly-codegen
> $ polly-opt
> test/ScopInfo/2012-03-16-Crash-because-of-unsigned-in-scev.ll
> -polly-codegen -polly-codegen-scev
> $ polly-opt
> test/ScopInfo/2012-03-16-Crash-because-of-unsigned-in-scev.ll
> -polly-codegen-isl
> $ polly-opt
> test/ScopInfo/2012-03-16-Crash-because-of-unsigned-in-scev.ll
> -polly-codegen-isl -polly-codegen-scev
> 
> Could you help me to reproduce this problem?

I was not able to reproduce the problem in the community version of polly.
It could be that we are exercising a different path with our changes.

Sebastian
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