This just copies the same conservative definition from mayWriteToMemory,
and enables more VPInstructions to be hoisted out in LICM.

I think this should give more accurate costs, and I was able to build
llvm-test-suite without the legacy-vplan cost model assertion going off.

When folding the tail, we may compute an address that we don't in the
original scalar loop and it may not be inbounds. Drop Inbounds in that
case.

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

Check the VPlan directly to determine if a VPValue is an optimiziable IV
or IV use instead of checking the underlying IR instructions.

Split off from https://github.com/llvm/llvm-project/pull/112147. This
refactoring enables moving IV end value creation from the legacy
fixupIVUsers to a VPlan-based transform.

There is one case we now won't optimize, that is IVs with subtracts and
non-constant steps. But as this is a minor optimization and doesn't
impact correctness, the benefits of performing the check in VPlan should
outweigh the missed case.

Update wide induction increments to use the same step as the corresponding
wide induction. This enables detecting induction increments directly in
VPlan and removes redundant splats.

Adds additional test coverage for induction codegen.

we generate GEPs that are out of bounds but mark them as "inbound"

Use createDerivedIV to compute IV end values directly in VPlan, instead
of creating them up-front.

This allows updating IV users outside the loop as follow-up.

Depends on https://github.com/llvm/llvm-project/pull/110004 and
https://github.com/llvm/llvm-project/pull/109975.

PR: https://github.com/llvm/llvm-project/pull/112145

printFlags() already takes care of printing a single space if there are
no flags. Remove the extra space when printing a recipe without flags.

When adding a new predicate to a union predicate, some of the existing
predicates may be implied by the new predicate. Remove any existing
predicates that are already implied by the new predicate.

Depends on https://github.com/llvm/llvm-project/pull/118184 to show the
main benefit.

PR: https://github.com/llvm/llvm-project/pull/118185