diff --git a/gcc/testsuite/g++.dg/opt/pr110515.C b/gcc/testsuite/g++.dg/opt/pr110515.C
new file mode 100644
index 00000000000..7a75cea3b4b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/opt/pr110515.C
@@ -0,0 +1,223 @@
+// { dg-do run }
+// { dg-require-effective-target c++11 }
+// { dg-options "-O2" }
+
+typedef __UINT64_TYPE__ u64;
+
+struct SmallDenseMap {
+  static constexpr u64 EmptyKey = 0xC0FFEUL;
+  struct V { u64 v; };
+
+  bool contains(u64 Val) {
+    V *TheSlot = nullptr;
+    return (LookupSlotFor(Val, TheSlot) ? 1 : 0);
+  }
+
+  void try_emplace(u64 Key) {
+    V *TheSlot = nullptr;
+    if (LookupSlotFor(Key, TheSlot))
+      return;
+
+    // Otherwise, insert the new element.
+    InsertIntoSlot(TheSlot, Key);
+  }
+
+  void moveFromOldSlots(V *OldSlotsBegin, V *OldSlotsEnd) {
+    Size = 0;
+
+    V *B_ = u.o.Slots;
+    V *E_ = B_ + u.o.Capacity;
+    for (; B_ != E_; ++B_)
+      B_->v = EmptyKey;
+
+    // Insert all the old elements.
+    V *O = OldSlotsBegin;
+    V *E = OldSlotsEnd;
+    for (; O != E; ++O) {
+      if (O->v != EmptyKey) {
+        // Insert the key/value into the new table.
+        V * N = nullptr;
+        LookupSlotFor(O->v, N);
+        N->v = O->v;
+        Size++;
+      }
+    }
+  }
+
+  void InsertIntoSlot(V *TheSlot, u64 Key) {
+    unsigned NewSize = Size + 1;
+    unsigned Capacity = getCapacity();
+    // Make sure we always keep at least one Empty value
+    if (NewSize >= Capacity) {
+      //fprintf(stderr, "GROW: size=%u capacity=%u -> ...\n", Size, Capacity);
+      grow();
+      LookupSlotFor(Key, TheSlot);
+      Capacity = getCapacity();
+      //fprintf(stderr, "GROW: ... -> size=%u capacity=%u\n", NewSize, Capacity);
+    }
+
+    Size++;
+
+    TheSlot->v = Key;
+  }
+
+  bool LookupSlotFor(u64 Val,
+                       V *&FoundSlot) {
+    V *SlotsPtr = getSlots();
+    const unsigned Capacity = getCapacity();
+
+    for (unsigned i = 0; i < Capacity; ++i) {
+      V *ThisSlot = SlotsPtr + i;
+      if (Val == ThisSlot->v) {
+        FoundSlot = ThisSlot;
+        return true;
+      }
+
+      if (ThisSlot->v == EmptyKey) {
+        FoundSlot = ThisSlot;
+        return false;
+      }
+    }
+    // Guarantee that within an array there is a match
+    // or Empty value where to insert a new vaue.
+    __builtin_trap();
+  }
+
+  // Needs to bea at least 1 to hld one empty value
+  static constexpr unsigned InlineSlots = 2;
+
+  bool Small;
+  unsigned Size;
+
+  struct LargeRep {
+    V *Slots;
+    unsigned Capacity;
+  };
+
+  union {
+      V i[InlineSlots]; // Small = true
+      LargeRep o;       // Small = false
+  } u;
+
+  explicit SmallDenseMap() : Small(true), Size(0) {
+    Size = 0;
+
+    V *B = u.i;
+    V *E = B + InlineSlots;
+    for (; B != E; ++B)
+      B->v = EmptyKey;
+  }
+
+  void grow() {
+    // assert:
+    if (!Small) __builtin_trap();
+
+    // First move the inline Slots into a temporary storage.
+    V TmpStorage[InlineSlots];
+    V *TmpBegin = TmpStorage;
+    V *TmpEnd = TmpBegin;
+
+    // Loop over the Slots, moving non-empty, non-tombstones into the
+    // temporary storage. Have the loop move the TmpEnd forward as it goes.
+    V *P = u.i;
+    V *E = P + InlineSlots;
+    for (; P != E; ++P) {
+        if (P->v != EmptyKey) {
+            TmpEnd->v = P->v;
+            ++TmpEnd;
+        }
+    }
+
+    Small = false;
+    u.o = LargeRep{new V[128], 128};
+    moveFromOldSlots(TmpBegin, TmpEnd);
+  }
+
+  V *getSlots() {
+    if (Small) {
+      V * inl = u.i;
+      return inl;
+    }
+    else {
+      LargeRep * rep = &u.o;
+      return rep->Slots;
+    }
+  }
+
+  unsigned getCapacity() {
+    if (Small) {
+      return InlineSlots;
+    }
+    else {
+      LargeRep * rep = &u.o;
+      return rep->Capacity;
+    }
+  }
+};
+
+#pragma GCC optimize(0)
+
+struct P {
+    u64 f;
+    bool s;
+};
+
+static u64 ws = 0;
+static P WorkList[128];
+
+__attribute__((noipa))
+static void popupateIni() {
+  for (u64 Var : (u64[]){8,7,6,5,4,3,0}) {
+    WorkList[ws++] = P{Var, false};
+  }
+}
+
+__attribute__((noipa))
+static void checkCycle(u64 Var) {
+    // Detect cycles.
+    static bool seen[256];
+    if (Var >= 256 || seen[Var]) __builtin_trap();
+    seen[Var] = true;
+}
+
+
+__attribute__((noipa))
+static void populateDeps(u64 Var) {
+
+    WorkList[ws++] = P{Var, true};
+    if (Var == 8)
+        WorkList[ws++] = P{0, false};
+}
+
+
+__attribute__((noipa)) __attribute__((optimize(3)))
+static void bug() {
+
+  // triggers growth on insert
+  SmallDenseMap Visited;
+
+  popupateIni();
+
+  while (ws > 0) {
+    P Item = WorkList[--ws];
+    u64 Var = Item.f;
+    bool visitedAllDependencies = Item.s;
+
+    if (Visited.contains(Var)) {
+      continue;
+    }
+
+    if (visitedAllDependencies) {
+      Visited.try_emplace(Var);
+      continue;
+    }
+
+    checkCycle(Var);
+    populateDeps(Var);
+  }
+}
+
+__attribute__((noipa))
+int main() {
+    bug();
+}
diff --git a/gcc/tree-ssa-pre.cc b/gcc/tree-ssa-pre.cc
index 37cad36f2de..7bc96ba95fa 100644
--- a/gcc/tree-ssa-pre.cc
+++ b/gcc/tree-ssa-pre.cc
@@ -4209,6 +4209,7 @@ compute_avail (function *fun)
 		      else
 			{
 			  ref->set = 0;
+			  ref->base_set = 0;
 			  if (ref1->opcode == MEM_REF)
 			    ref1->op0
 			      = wide_int_to_tree (ptr_type_node,