From 67f9c87a651a9c3a57a2b1bf32e6e0be2479ebc7 Mon Sep 17 00:00:00 2001
From: Roman Lebedev <lebedev.ri@gmail.com>
Date: Sat, 23 Jan 2021 22:01:41 +0300
Subject: [PATCH] [NFC][SimplifyCFG] Perform early-continue in
 FoldValueComparisonIntoPredecessors() per-pred loop

---
 llvm/lib/Transforms/Utils/SimplifyCFG.cpp | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 318e6d5..6dab65d 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1273,24 +1273,27 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(Instruction *TI,
   SmallSetVector<BasicBlock *, 16> Preds(pred_begin(BB), pred_end(BB));
   while (!Preds.empty()) {
     BasicBlock *Pred = Preds.pop_back_val();
+    Instruction *PTI = Pred->getTerminator();
+
+    // Don't try to fold into itself.
+    if (Pred == BB)
+      continue;
 
     // See if the predecessor is a comparison with the same value.
-    Instruction *PTI = Pred->getTerminator();
     Value *PCV = isValueEqualityComparison(PTI); // PredCondVal
+    if (PCV != CV)
+      continue;
 
-    if (PCV == CV && TI != PTI) {
-      SmallSetVector<BasicBlock*, 4> FailBlocks;
-      if (!SafeToMergeTerminators(TI, PTI, &FailBlocks)) {
-        for (auto *Succ : FailBlocks) {
-          if (!SplitBlockPredecessors(Succ, TI->getParent(), ".fold.split",
-                                      DTU))
-            return false;
-        }
+    SmallSetVector<BasicBlock *, 4> FailBlocks;
+    if (!SafeToMergeTerminators(TI, PTI, &FailBlocks)) {
+      for (auto *Succ : FailBlocks) {
+        if (!SplitBlockPredecessors(Succ, TI->getParent(), ".fold.split", DTU))
+          return false;
       }
-
-      PerformValueComparisonIntoPredecessorFolding(TI, CV, PTI, Builder);
-      Changed = true;
     }
+
+    PerformValueComparisonIntoPredecessorFolding(TI, CV, PTI, Builder);
+    Changed = true;
   }
   return Changed;
 }
-- 
2.7.4