[llvm] [VPlan] Replace reverse RPOT with PO traversal (NFC) (PR #151757)

[Ramkumar Ramachandra via llvm-commits]

https://github.com/artagnon created https://github.com/llvm/llvm-project/pull/151757

None

>From 4d3c205fc08eebdd6803fbba4f12f6049a4c1da5 Mon Sep 17 00:00:00 2001
From: Ramkumar Ramachandra <ramkumar.ramachandra at codasip.com>
Date: Fri, 1 Aug 2025 20:33:32 +0100
Subject: [PATCH] [VPlan] Replace reverse RPOT with PO traversal (NFC)

---
 llvm/lib/Transforms/Vectorize/VPlanCFG.h          | 8 ++++++++
 llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp | 6 ++----
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/llvm/lib/Transforms/Vectorize/VPlanCFG.h b/llvm/lib/Transforms/Vectorize/VPlanCFG.h
index b77aa9d710ef0..9a11258b8aded 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanCFG.h
+++ b/llvm/lib/Transforms/Vectorize/VPlanCFG.h
@@ -230,6 +230,14 @@ vp_post_order_shallow(VPBlockBase *G) {
   return post_order(VPBlockShallowTraversalWrapper<VPBlockBase *>(G));
 }
 
+/// Returns an iterator range to traverse the graph starting at \p G in
+/// post order while traversing through region blocks.
+inline iterator_range<
+    po_iterator<VPBlockDeepTraversalWrapper<VPBlockBase *>>>
+vp_post_order_deep(VPBlockBase *G) {
+  return post_order(VPBlockDeepTraversalWrapper<VPBlockBase *>(G));
+}
+
 /// Returns an iterator range to traverse the graph starting at \p G in
 /// depth-first order while traversing through region blocks.
 inline iterator_range<df_iterator<VPBlockDeepTraversalWrapper<VPBlockBase *>>>
diff --git a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
index fcbc86f5e4c58..4222d88380382 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
@@ -545,10 +545,8 @@ static bool isDeadRecipe(VPRecipeBase &R) {
 }
 
 void VPlanTransforms::removeDeadRecipes(VPlan &Plan) {
-  ReversePostOrderTraversal<VPBlockDeepTraversalWrapper<VPBlockBase *>> RPOT(
-      Plan.getEntry());
-
-  for (VPBasicBlock *VPBB : reverse(VPBlockUtils::blocksOnly<VPBasicBlock>(RPOT))) {
+  for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(
+           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))) {