[llvm] r222093 - ScalarEvolution: HowFarToZero was wrongly using signed division

[Tobias Grosser]

On 16.11.2014 08:30, David Majnemer wrote:
> Author: majnemer
> Date: Sun Nov 16 01:30:35 2014
> New Revision: 222093
>
> URL: http://llvm.org/viewvc/llvm-project?rev=222093&view=rev
> Log:
> ScalarEvolution: HowFarToZero was wrongly using signed division
>
> HowFarToZero was supposed to use unsigned division in order to calculate
> the backedge taken count.  However, SCEVDivision::divide performs signed
> division.  Unless I am mistaken, no users of SCEVDivision actually want
> signed arithmetic: switch to udiv and urem.
>
> This fixes PR21578.

This commit breaks a delinearization test case in polly.

I copied Sebastian who originally wrote the divide operation exactly as 
part of our delinearization analysis. He is possibly the best person to 
comment on this.

Cheers,
Tobias