[llvm] [SimplifyCFG] Fix hoisting problem in SimplifyCFG (PR #78615)

[via llvm-commits]

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@@ -1589,80 +1610,121 @@ bool SimplifyCFGOpt::hoistCommonCodeFromSuccessors(BasicBlock *BB,
   }
 
   bool Changed = false;
+  auto *SuccIterPairBegin = SuccIterPairs.begin();
+  SuccIterPairBegin++;
+  auto OtherSuccIterPairRange =
+      iterator_range(SuccIterPairBegin, SuccIterPairs.end());
+  auto OtherSuccIterRange = make_first_range(OtherSuccIterPairRange);
+  using InstrFlagPair = std::pair<Instruction *, unsigned>;
+  SmallVector<DenseMap<llvm::hash_code, InstrFlagPair>, 2> OtherSuccessorsHash;
+
+  for (auto BBItrPair : OtherSuccIterRange) {
+    // Fill the hashmap for every other successor
+    DenseMap<llvm::hash_code, InstrFlagPair> hashMap;
+    unsigned skipFlag = 0;
+    Instruction *I = nullptr;
+    do {
+      I = &*BBItrPair;
+      skipFlag |= skippedInstrFlags(I);
+      hashMap[getHash(I)] = InstrFlagPair(I, skipFlag);
+      BBItrPair++;
+    } while (!I->isTerminator());
+    OtherSuccessorsHash.push_back(hashMap);
+  }
 
+  // Keep track of instructions skipped in the first successor
+  unsigned SkipFlagsBB1 = 0;
+  bool SameLevelHoist = true;
   for (;;) {
     auto *SuccIterPairBegin = SuccIterPairs.begin();
     auto &BB1ItrPair = *SuccIterPairBegin++;
     auto OtherSuccIterPairRange =
         iterator_range(SuccIterPairBegin, SuccIterPairs.end());
-    auto OtherSuccIterRange = make_first_range(OtherSuccIterPairRange);
-
     Instruction *I1 = &*BB1ItrPair.first;
     auto *BB1 = I1->getParent();
-
-    // Skip debug info if it is not identical.
-    bool AllDbgInstsAreIdentical = all_of(OtherSuccIterRange, [I1](auto &Iter) {
-      Instruction *I2 = &*Iter;
-      return I1->isIdenticalToWhenDefined(I2);
-    });
-    if (!AllDbgInstsAreIdentical) {
-      while (isa<DbgInfoIntrinsic>(I1))
-        I1 = &*++BB1ItrPair.first;
-      for (auto &SuccIter : OtherSuccIterRange) {
-        Instruction *I2 = &*SuccIter;
-        while (isa<DbgInfoIntrinsic>(I2))
-          I2 = &*++SuccIter;
+    bool HasIdenticalInst = true;
+
+    // Check if there are identical instructions in all other successors
+    for (auto &map : OtherSuccessorsHash) {
+      Instruction *I2 = map[getHash(I1)].first;
+      // We might face with same hash values for different instructions.
+      // If that happens, ignore the instruction.
+      if (!I2 || !I1->isIdenticalTo(I2)) {
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RouzbehPaktinat wrote:

Fixed it.

https://github.com/llvm/llvm-project/pull/78615