[llvm] [VPlan] Free removeDeadRecipes from VPPhi simplification (PR #156438)

[Luke Lau via llvm-commits]

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@@ -555,24 +555,9 @@ void VPlanTransforms::removeDeadRecipes(VPlan &Plan) {
            vp_post_order_deep(Plan.getEntry()))) {
     // The recipes in the block are processed in reverse order, to catch chains
     // of dead recipes.
-    for (VPRecipeBase &R : make_early_inc_range(reverse(*VPBB))) {
-      if (isDeadRecipe(R)) {
+    for (VPRecipeBase &R : make_early_inc_range(reverse(*VPBB)))
+      if (isDeadRecipe(R))
         R.eraseFromParent();
-        continue;
-      }
-
-      // Check if R is a dead VPPhi <-> update cycle and remove it.
-      auto *PhiR = dyn_cast<VPPhi>(&R);
-      if (!PhiR || PhiR->getNumOperands() != 2 || PhiR->getNumUsers() != 1)
-        continue;
-      VPValue *Incoming = PhiR->getOperand(1);
-      if (*PhiR->user_begin() != Incoming->getDefiningRecipe() ||
-          Incoming->getNumUsers() != 1)
-        continue;
-      PhiR->replaceAllUsesWith(PhiR->getOperand(0));
-      PhiR->eraseFromParent();
-      Incoming->getDefiningRecipe()->eraseFromParent();
-    }
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lukel97 wrote:

I would have thought deleting VPPhis in removeDeadRecipes would have been a generally better place? Some transforms call `removeDeadRecipes` to cleanup and this means that there will still be some dead VPPhi cycles lying around until the next call to `simplifyRecipes`. 

https://github.com/llvm/llvm-project/pull/156438