[PATCH] D135137: [AggressiveInstCombine] Load merge the reverse load pattern of consecutive loads.

[Evgeny Eltsin via Phabricator via llvm-commits]

eaeltsin added a comment.

Here is the reproducer - https://godbolt.org/z/7bcjzfYK4

The following program returns 33 on trunk and 0 on clang 14:

  #include <utility>
  
  template <typename ValueType>
  class Cell {
   public:
    Cell() = default;
  
    void Set(ValueType value) {
      value_ = value;
      has_data_ = true;
    }
    std::pair<ValueType, bool> GetAndMarkRead() {
      bool fresh = has_data_;
      has_data_ = false;
      return std::make_pair(value_, fresh);
    }
    bool GetAndMarkRead2() {
      bool fresh = has_data_;
      has_data_ = false;
      return fresh;
    }
  
    ValueType value_;
    bool has_data_ = false;
  };
  
  bool foo() {
    Cell<bool> cell;
    cell.Set(true);
    return cell.GetAndMarkRead().second;
  }
  
  int main() {
      if (foo()) return 0;
      return 33;
  }

`GetAndMarkRead` returns `false` instead of 'true`. Returning `std::pair` matters.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D135137/new/

https://reviews.llvm.org/D135137