[PATCH] D148966: [SLP] Cleanup: Remove loop around `tryToVectorizeSequence` of PHIs.

[Vasileios Porpodas via Phabricator via llvm-commits]

vporpo created this revision.
vporpo added a reviewer: ABataev.
Herald added a subscriber: hiraditya.
Herald added a project: All.
vporpo requested review of this revision.
Herald added subscribers: llvm-commits, pcwang-thead.
Herald added a project: LLVM.

I think that the loop is not needed.
I added an assertion to check whether a second iteration succeeds in
vectorizing phi noeds, but it never caused a crash.
Anyway, if this is actually used, we don't have a test for it.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D148966

Files:
  llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp


Index: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -14501,53 +14501,50 @@
   };
 
   bool HaveVectorizedPhiNodes = false;
-  do {
-    // Collect the incoming values from the PHIs.
-    Incoming.clear();
-    for (Instruction &I : *BB) {
-      PHINode *P = dyn_cast<PHINode>(&I);
-      if (!P)
-        break;
+  // Collect the incoming values from the PHIs.
+  Incoming.clear();
+  for (Instruction &I : *BB) {
+    PHINode *P = dyn_cast<PHINode>(&I);
+    if (!P)
+      break;
 
-      // No need to analyze deleted, vectorized and non-vectorizable
-      // instructions.
-      if (!VisitedInstrs.count(P) && !R.isDeleted(P) &&
-          isValidElementType(P->getType()))
-        Incoming.push_back(P);
-    }
+    // No need to analyze deleted, vectorized and non-vectorizable
+    // instructions.
+    if (!VisitedInstrs.count(P) && !R.isDeleted(P) &&
+        isValidElementType(P->getType()))
+      Incoming.push_back(P);
+  }
 
-    // Find the corresponding non-phi nodes for better matching when trying to
-    // build the tree.
-    for (Value *V : Incoming) {
-      SmallVectorImpl<Value *> &Opcodes =
-          PHIToOpcodes.try_emplace(V).first->getSecond();
-      if (!Opcodes.empty())
+  // Find the corresponding non-phi nodes for better matching when trying to
+  // build the tree.
+  for (Value *V : Incoming) {
+    SmallVectorImpl<Value *> &Opcodes =
+        PHIToOpcodes.try_emplace(V).first->getSecond();
+    if (!Opcodes.empty())
+      continue;
+    SmallVector<Value *, 4> Nodes(1, V);
+    SmallPtrSet<Value *, 4> Visited;
+    while (!Nodes.empty()) {
+      auto *PHI = cast<PHINode>(Nodes.pop_back_val());
+      if (!Visited.insert(PHI).second)
         continue;
-      SmallVector<Value *, 4> Nodes(1, V);
-      SmallPtrSet<Value *, 4> Visited;
-      while (!Nodes.empty()) {
-        auto *PHI = cast<PHINode>(Nodes.pop_back_val());
-        if (!Visited.insert(PHI).second)
+      for (Value *V : PHI->incoming_values()) {
+        if (auto *PHI1 = dyn_cast<PHINode>((V))) {
+          Nodes.push_back(PHI1);
           continue;
-        for (Value *V : PHI->incoming_values()) {
-          if (auto *PHI1 = dyn_cast<PHINode>((V))) {
-            Nodes.push_back(PHI1);
-            continue;
-          }
-          Opcodes.emplace_back(V);
         }
+        Opcodes.emplace_back(V);
       }
     }
+  }
 
-    HaveVectorizedPhiNodes = tryToVectorizeSequence<Value>(
-        Incoming, PHICompare, AreCompatiblePHIs,
-        [this, &R](ArrayRef<Value *> Candidates, bool LimitForRegisterSize) {
-          return tryToVectorizeList(Candidates, R, LimitForRegisterSize);
-        },
-        /*LimitForRegisterSize=*/true, R);
-    Changed |= HaveVectorizedPhiNodes;
-    VisitedInstrs.insert(Incoming.begin(), Incoming.end());
-  } while (HaveVectorizedPhiNodes);
+  HaveVectorizedPhiNodes = tryToVectorizeSequence<Value>(
+      Incoming, PHICompare, AreCompatiblePHIs,
+      [this, &R](ArrayRef<Value *> Candidates, bool LimitForRegisterSize) {
+        return tryToVectorizeList(Candidates, R, LimitForRegisterSize);
+      },
+      /*LimitForRegisterSize=*/true, R);
+  Changed |= HaveVectorizedPhiNodes;
 
   VisitedInstrs.clear();
 


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