[llvm] r270629 - [LoopUnrollAnalyzer] Fix a crash in UnrolledInstAnalyzer::visitCastInst.

[Eli Friedman via llvm-commits]

On Tue, May 24, 2016 at 5:57 PM, Michael Zolotukhin <mzolotukhin at apple.com>
wrote:

>
> On May 24, 2016, at 5:47 PM, Eli Friedman <eli.friedman at gmail.com> wrote:
> How are you getting into a situation where "V.getType() !=
> SimplifiedValues.lookup(V).getType()"?  It seems like there's an underlying
> problem which is getting ignored here.
>
> It happens when SCEV analyzes an instruction like
> %offset = getelementptr inbounds float, float* null, i32 3
>

Ah, I see, SCEVConstant::getValue returns a ConstantInt.  That's probably
reasonable from the perspective of SCEV, since it fundamentally always
works with integers.

When asked for a value at some iteration, SCEV considers ‘null' as 0 and
> returns, for instance, ‘i32 24’. I’m not sure if it’s incorrect, that’s why
> I fixed it in this spot.
>

Maybe you could construct an inttoptr constant expression in
UnrolledInstAnalyzer::simplifyInstWithSCEV instead of trying to recover
later?

-Eli
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