Introduce a VPlan-level constant folder in simplifyRecipe that tries to
fold a recipe to a constant using TargetFolder.

Add a new convertToUniformRecipes transform which uses VPlan-based
uniformity analysis to determine if wide recipes and replicate recipes
can be converted to uniform recipes.

There are a few places where we ad-hoc convert recipes to uniform
recipes, which this transform will eventually replace. There are a few
more generalizations required to do so which I plan to do as follow-ups.

By converting the recipes to uniform recipes, we effectively materialize
the information from the VPlan-based analysis.

Note that there is one regression at the moment in SystemZ/pr47665.ll
due to trivial constant folding opportunities in the input IR. This will
be fixed by VPlan-based constant folding
(https://github.com/llvm/llvm-project/pull/125365/)

PR: https://github.com/llvm/llvm-project/pull/139150

Follow-up to 0f607f to actually use the captured operand X instead of Y.

Add additional OR simplification to fix a divergence between legacy and
VPlan-based cost model.

This adds a new m_AllOnes matcher by generalizing specific_intval to
int_pred_ty, which takes a predicate to check to support matching both
specific APInts and other APInt predices, like isAllOnes.

Fixes https://github.com/llvm/llvm-project/issues/131359.

Add an initial CFG simplification transform, which removes the dead
edges for blocks terminated with BranchOnCond true.

At the moment, this removes the edge between middle block and scalar
preheader when folding the tail.

PR: https://github.com/llvm/llvm-project/pull/106748

Update optimizeForVFAndUF to completely remove the vector loop region
when possible. At the moment, we cannot remove the region if it contains

* widened IVs: the recipe is needed to generate the step vector
* reductions: ComputeReductionResults requires the reduction phi recipe
for codegen.

Both cases can be addressed by more explicit modeling.

The patch also includes a number of updates to allow executing VPlans
without a vector loop region.

Depends on https://github.com/llvm/llvm-project/pull/110004

If IVUpdateMayOverflow is false, we proved that the induction increment
cannot overflow in the vector loop. This allows setting NUW in some
cases when folding the tail.

PR: https://github.com/llvm/llvm-project/pull/111758

Update isDefinedOutsideLoopRegions to check if a recipe is defined
outside any region. Split off already approved
https://github.com/llvm/llvm-project/pull/95842 now that this can be
tested separately after landing VPlan-based LICM
https://github.com/llvm/llvm-project/issues/107501

Add initial transform to move out loop-invariant recipes.

This also helps to fix a divergence between legacy and VPlan-based cost
model due to legacy using ScalarEvolution::isLoopInvariant in some
cases.

Fixes https://github.com/llvm/llvm-project/issues/107501.

PR: https://github.com/llvm/llvm-project/pull/107894