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

[Florian Hahn via llvm-commits]

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@@ -696,16 +696,46 @@ void VPlanTransforms::optimizeForVFAndUF(VPlan &Plan, ElementCount BestVF,
       !SE.isKnownPredicate(CmpInst::ICMP_ULE, TripCount, C))
     return;
 
-  LLVMContext &Ctx = SE.getContext();
-  auto *BOC =
-      new VPInstruction(VPInstruction::BranchOnCond,
-                        {Plan.getOrAddLiveIn(ConstantInt::getTrue(Ctx))});
-
   SmallVector<VPValue *> PossiblyDead(Term->operands());
   Term->eraseFromParent();
+  VPBasicBlock *Header =
+      cast<VPBasicBlock>(Plan.getVectorLoopRegion()->getEntry());
+  if (all_of(Header->phis(), [](VPRecipeBase &R) {
+        return !isa<VPWidenIntOrFpInductionRecipe, VPReductionPHIRecipe>(&R);
+      })) {
+    for (VPRecipeBase &R : make_early_inc_range(Header->phis())) {
+      auto *P = cast<VPHeaderPHIRecipe>(&R);
+      P->replaceAllUsesWith(P->getStartValue());
+      P->eraseFromParent();
+    }
+
+    VPBlockBase *Preheader = Plan.getVectorLoopRegion()->getSinglePredecessor();
+    auto HeaderSuccs = to_vector(Header->getSuccessors());
+    VPBasicBlock *Exiting =
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fhahn wrote:

Done, thanks! 

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