[llvm] [VPlan] Remove loop region in optimizeForVFAndUF. (PR #108378)

[via llvm-commits]

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@@ -1015,49 +1013,51 @@ void VPlan::execute(VPTransformState *State) {
   for (VPBlockBase *Block : RPOT)
     Block->execute(State);
 
-  VPBasicBlock *LatchVPBB = getVectorLoopRegion()->getExitingBasicBlock();
-  BasicBlock *VectorLatchBB = State->CFG.VPBB2IRBB[LatchVPBB];
-
-  // Fix the latch value of canonical, reduction and first-order recurrences
-  // phis in the vector loop.
-  VPBasicBlock *Header = getVectorLoopRegion()->getEntryBasicBlock();
-  for (VPRecipeBase &R : Header->phis()) {
-    // Skip phi-like recipes that generate their backedege values themselves.
-    if (isa<VPWidenPHIRecipe>(&R))
-      continue;
-
-    if (isa<VPWidenInductionRecipe>(&R)) {
-      PHINode *Phi = nullptr;
-      if (isa<VPWidenIntOrFpInductionRecipe>(&R)) {
-        Phi = cast<PHINode>(State->get(R.getVPSingleValue()));
-      } else {
-        auto *WidenPhi = cast<VPWidenPointerInductionRecipe>(&R);
-        assert(!WidenPhi->onlyScalarsGenerated(State->VF.isScalable()) &&
-               "recipe generating only scalars should have been replaced");
-        auto *GEP = cast<GetElementPtrInst>(State->get(WidenPhi));
-        Phi = cast<PHINode>(GEP->getPointerOperand());
-      }
+  if (auto *LoopRegion = getVectorLoopRegion()) {
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ayalz wrote:

nit: early-exit would reduce troubled diff, but requires duplicating `State->CFG.DTU.flush();`

https://github.com/llvm/llvm-project/pull/108378