This patch moves branch condition creation to enter the scalar epilogue
loop to VPlan. Modeling the branch in the middle block also requires
modeling the successor blocks. This is done using the recently
introduced VPIRBasicBlock.
Note that the middle.block is still created as part of the skeleton and
then patched in during VPlan execution. Unfortunately the skeleton needs
to create the middle.block early on, as it is also used for induction
resume value creation and is also needed to properly update the
dominator tree during skeleton creation.
After this patch lands, I plan to move induction resume value and phi
node creation in the scalar preheader to VPlan. Once that is done, we
should be able to create the middle.block in VPlan directly.
This is a re-worked version based on the earlier
https://reviews.llvm.org/D150398 and the main change is the use of
VPIRBasicBlock.
Depends on https://github.com/llvm/llvm-project/pull/92525
PR: https://github.com/llvm/llvm-project/pull/92651
CanonicalIVIncrementForPart uses VPIteration(0, 0) of the IV (first
operand), mark it as only using part 0.
This avoids generating redundant IV increments per part.
pr73894.ll is failing on a number of non-AArch64 buildbots. I'm not
certain that this is a proper fix, but I think it's best to move the
test to the test/Transforms/LoopVectorize/AArch64/ directory and replace
the triple with one commonly used in that directory.
llvm#73894
