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//===- LCSSA.h - Loop-closed SSA transform Pass -----------------*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

// This pass transforms loops by placing phi nodes at the end of the loops for

// all values that are live across the loop boundary.  For example, it turns

// the left into the right code:

//

// for (...)                for (...)

//   if (c)                   if (c)

//     X1 = ...                 X1 = ...

//   else                     else

//     X2 = ...                 X2 = ...

//   X3 = phi(X1, X2)         X3 = phi(X1, X2)

// ... = X3 + 4             X4 = phi(X3)

//                          ... = X4 + 4

//

// This is still valid LLVM; the extra phi nodes are purely redundant, and will

// be trivially eliminated by InstCombine.  The major benefit of this

// transformation is that it makes many other loop optimizations, such as

// LoopUnswitching, simpler.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_TRANSFORMS_UTILS_LCSSA_H

#define LLVM_TRANSFORMS_UTILS_LCSSA_H

#include "llvm/IR/PassManager.h"

namespace llvm {

/// Converts loops into loop-closed SSA form.

class LCSSAPass : public PassInfoMixin<LCSSAPass> {

public:

  PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);

};

} // end namespace llvm

#endif // LLVM_TRANSFORMS_UTILS_LCSSA_H