SCEV: add samesign tests for exit-limit computation (#124304)

As the tests demonstrate, computeExitLimitFromICmp needs no additional
changes to compute exit limits from an icmp with samesign.

[Analysis] Teach isDereferenceableAndAlignedInLoop about SCEV predicates (#106562)

Currently if a loop contains loads that we can prove at compile time
are dereferenceable when certain conditions a

[Analysis] Teach isDereferenceableAndAlignedInLoop about SCEV predicates (#106562)

Currently if a loop contains loads that we can prove at compile time
are dereferenceable when certain conditions are satisfied the function
isDereferenceableAndAlignedInLoop will still return false because
getSmallConstantMaxTripCount will return 0 when SCEV predicates
are required. This patch changes getSmallConstantMaxTripCount to take
an optional Predicates pointer argument so that we can permit
functions such as isDereferenceableAndAlignedInLoop to consider more
cases.

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[Analysis] Add getPredicatedExitCount to ScalarEvolution (#105649)

Due to a reviewer request on PR #88385 I have created this patch
to add a getPredicatedExitCount function, which is similar to
ge

[Analysis] Add getPredicatedExitCount to ScalarEvolution (#105649)

Due to a reviewer request on PR #88385 I have created this patch
to add a getPredicatedExitCount function, which is similar to
getExitCount except that it uses the predicated backedge taken
information. With PR #88385 we will start to care about more
loops with multiple exits, and want the ability to query exit
counts for a particular exiting block. Such loops may require
predicates in order to be vectorised.

New tests added here:

Analysis/ScalarEvolution/predicated-exit-count.ll

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[SCEV] Support ule/sle exit counts via widening (#92206)

If we have an exit condition of the form IV <= Limit, we will first try
to convert it into IV < Limit+1 or IV-1 < Limit based on range info

[SCEV] Support ule/sle exit counts via widening (#92206)

If we have an exit condition of the form IV <= Limit, we will first try
to convert it into IV < Limit+1 or IV-1 < Limit based on range info (in
icmp simplification). If that fails, we try to convert it to IV < Limit
+ 1 based on controlling exits in non-infinite loops.

However, if all else fails, we can still determine the exit count by
rewriting to ext(IV) < ext(Limit) + 1, where the zero/sign extension
ensures that the addition does not overflow.

Proof: https://alive2.llvm.org/ce/z/iR-iYd

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[SCEV] Add tests for ule/sle exit counts (NFC)