[llvm] [VPlan] Delay adding canonical IV increment and exit branches. (PR #82270)

[Florian Hahn via llvm-commits]

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@@ -1572,3 +1529,71 @@ void VPlanTransforms::dropPoisonGeneratingRecipes(
     }
   }
 }
+
+void VPlanTransforms::finalizePlan(VPlan &Plan, bool HasNUW,
+                                   bool DataAndControlFlowWithoutRuntimeCheck) {
+  auto *CanIV = Plan.getCanonicalIV();
+
+  VPBasicBlock *EB = Plan.getVectorLoopRegion()->getExitingBasicBlock();
+  VPBuilder Builder(EB);
+  DebugLoc DL = CanIV->getDebugLoc();
+  // Add a VPInstruction to increment the scalar canonical IV by VF * UF.
+  auto *CanonicalIVIncrement =
+      Builder.createOverflowingOp(Instruction::Add, {CanIV, &Plan.getVFxUF()},
+                                  {HasNUW, false}, DL, "index.next");
+
+  CanIV->addOperand(CanonicalIVIncrement);
+
+  auto FoundLaneMaskPhi = find_if(
+      Plan.getVectorLoopRegion()->getEntryBasicBlock()->phis(),
+      [](VPRecipeBase &P) { return isa<VPActiveLaneMaskPHIRecipe>(P); });
+
+  if (FoundLaneMaskPhi ==
+      Plan.getVectorLoopRegion()->getEntryBasicBlock()->phis().end()) {
+    // Add the BranchOnCount VPInstruction to the latch.
+    Builder.createNaryOp(VPInstruction::BranchOnCount,
+                         {CanonicalIVIncrement, &Plan.getVectorTripCount()},
+                         DL);
+    return;
+  }
+  auto *LaneMaskPhi = cast<VPActiveLaneMaskPHIRecipe>(&*FoundLaneMaskPhi);
----------------
fhahn wrote:

Done thanks!

https://github.com/llvm/llvm-project/pull/82270