[llvm] [Attributor] Change allocation size and load/store offsets using AAPointerInfo for Alloca instructions (PR #72029)

[Vidush Singhal via llvm-commits]

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@@ -6108,6 +6102,52 @@ struct AAPointerInfo : public AbstractAttribute {
     Type *Ty;
   };
 
+  /// A helper containing a list of offsets computed for a Use. Ideally this
+  /// 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 = SmallVector<int64_t>;
+    using const_iterator = VecTy::const_iterator;
+    VecTy Offsets;
+
+    const_iterator begin() const { return Offsets.begin(); }
+    const_iterator end() const { return Offsets.end(); }
+
+    bool operator==(const OffsetInfo &RHS) const {
+      return Offsets == RHS.Offsets;
+    }
+
+    bool operator!=(const OffsetInfo &RHS) const { return !(*this == RHS); }
+
+    void insert(int64_t Offset) { Offsets.push_back(Offset); }
+    bool isUnassigned() const { return Offsets.size() == 0; }
+
+    bool isUnknown() const {
+      if (isUnassigned())
+        return false;
+      if (Offsets.size() == 1)
+        return Offsets.front() == AA::RangeTy::Unknown;
+      return false;
+    }
+
+    void setUnknown() {
+      Offsets.clear();
+      Offsets.push_back(AA::RangeTy::Unknown);
+    }
+
+    void addToAll(int64_t Inc) {
+      for (auto &Offset : Offsets) {
+        Offset += Inc;
+      }
+    }
+
+    /// Copy offsets from \p R into the current list.
+    ///
+    /// Ideally all lists should be strictly ascending, but we defer that to the
+    /// actual use of the list. So we just blindly append here.
+    void merge(const OffsetInfo &R) { Offsets.append(R.Offsets); }
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vidsinghal wrote:

it might cause duplication, it should be unique I think. 

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