[llvm] [VPlan] Compute induction end values in VPlan. (PR #112145)

[Florian Hahn via llvm-commits]

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@@ -10299,6 +10292,39 @@ bool LoopVectorizePass::processLoop(Loop *L) {
                                            EPI, &LVL, &CM, BFI, PSI, Checks,
                                            *BestMainPlan);
 
+        // Collect PHI nodes of wide inductions in the VPlan for the epilogue.
+        // Those will need their resume-values computed from the main vector
+        // loop. Others can be removed in the main VPlan.
+        SmallPtrSet<PHINode *, 2> WidenedPhis;
+        for (VPRecipeBase &R :
+             BestEpiPlan.getVectorLoopRegion()->getEntryBasicBlock()->phis()) {
+          if (!isa<VPWidenIntOrFpInductionRecipe,
+                   VPWidenPointerInductionRecipe>(&R))
+            continue;
+          if (isa<VPWidenIntOrFpInductionRecipe>(&R))
+            WidenedPhis.insert(
+                cast<VPWidenIntOrFpInductionRecipe>(&R)->getPHINode());
+          else
+            WidenedPhis.insert(
+                cast<PHINode>(R.getVPSingleValue()->getUnderlyingValue()));
+        }
+        for (VPRecipeBase &R :
+             *cast<VPIRBasicBlock>(BestMainPlan->getScalarHeader())) {
+          auto *VPIRInst = cast<VPIRInstruction>(&R);
+          auto *IRI = dyn_cast<PHINode>(&VPIRInst->getInstruction());
+          if (!IRI)
+            break;
+          if (WidenedPhis.contains(IRI) ||
+              !LVL.getInductionVars().contains(IRI))
+            continue;
+          VPRecipeBase *ResumePhi =
+              VPIRInst->getOperand(0)->getDefiningRecipe();
+          VPIRInst->setOperand(0, BestMainPlan->getOrAddLiveIn(
+                                      Constant::getNullValue(IRI->getType())));
+          ResumePhi->eraseFromParent();
+        }
+        VPlanTransforms::removeDeadRecipes(*BestMainPlan);
+
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fhahn wrote:

Outlined, thanks!

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