[llvm] [Attributor] Change allocation size and load/store offsets using AAPointerInfo for Alloca instructions and keep track of instructions causing an Access (PR #72029)

[Vidush Singhal via llvm-commits]

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@@ -5858,49 +5866,161 @@ struct AAPointerInfo : public AbstractAttribute {
   /// list should be strictly ascending, but we ensure that only when we
   /// actually translate the list of offsets to a RangeList.
   struct OffsetInfo {
-    using VecTy = SmallSet<int64_t, 4>;
+    using VecTy = SmallVector<AA::RangeTy>;
+    // A map to store depth 1 predecessors per offset.
+    using OriginsTy = SmallVector<SmallPtrSet<Value *, 4>>;
     using const_iterator = VecTy::const_iterator;
-    VecTy Offsets;
+    OriginsTy Origins;
+    VecTy Ranges;
 
-    const_iterator begin() const { return Offsets.begin(); }
-    const_iterator end() const { return Offsets.end(); }
+    const_iterator begin() const { return Ranges.begin(); }
+    const_iterator end() const { return Ranges.end(); }
 
     bool operator==(const OffsetInfo &RHS) const {
-      return Offsets == RHS.Offsets;
+      return Ranges == RHS.Ranges && Origins == RHS.Origins;
     }
 
     bool operator!=(const OffsetInfo &RHS) const { return !(*this == RHS); }
 
-    bool insert(int64_t Offset) { return Offsets.insert(Offset).second; }
-    bool isUnassigned() const { return Offsets.size() == 0; }
+    // Insert a new Range and Origin
+    void insert(AA::RangeTy Range, Value &V) {
+      auto *It = std::find(Ranges.begin(), Ranges.end(), Range);
+      // Offset exists in Offsets map
+      if (It != Ranges.end()) {
+        size_t Index = It - Ranges.begin();
+        if (Index < Origins.size())
+          Origins[Index].insert(&V);
+      } else {
+        Ranges.push_back(Range);
+        Origins.emplace_back();
+        Origins.back().insert(&V);
+      }
+    }
+
+    // Set the size of the offset for all ranges.
+    void setSizeAll(uint64_t Size) {
+      for (auto &Range : Ranges)
+        Range.Size = Size;
+    }
+
+    // Helper function to get just the offsets from Ranges.
+    void getOnlyOffsets(SmallVector<int64_t> &Offsets) {
+      for (auto &Range : Ranges)
+        Offsets.push_back(Range.Offset);
+      // ensure unique
+      sort(Offsets.begin(), Offsets.end());
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vidsinghal wrote:

We need sortedness property, I believe SmallSetVector is immutable so we cannot sort in place. 
I would therefore, stick with SmallVector

https://github.com/llvm/llvm-project/pull/72029