GVN.h

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//===- GVN.h - Eliminate redundant values and loads -------------*- 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
//
//===----------------------------------------------------------------------===//
/// \file
/// This file provides the interface for LLVM's Global Value Numbering pass
/// which eliminates fully redundant instructions. It also does somewhat Ad-Hoc
/// PRE and dead load elimination.
///
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_TRANSFORMS_SCALAR_GVN_H
#define LLVM_TRANSFORMS_SCALAR_GVN_H
 
#include "llvm/IR/PassManager.h"
#include <memory>
#include <optional>
 
namespace llvm {
 
class FunctionPass;
class GVNPassImpl;
 
/// A set of parameters to control various transforms performed by GVN pass.
//  Each of the optional boolean parameters can be set to:
///      true - enabling the transformation.
///      false - disabling the transformation.
///      None - relying on a global default.
/// Intended use is to create a default object, modify parameters with
/// additional setters and then pass it to GVN.
struct GVNOptions {
  std::optional<bool> AllowScalarPRE;
  std::optional<bool> AllowLoadPRE;
  std::optional<bool> AllowLoadInLoopPRE;
  std::optional<bool> AllowLoadPRESplitBackedge;
  std::optional<bool> AllowMemDep;
  std::optional<bool> AllowMemorySSA;
 
  GVNOptions() = default;
 
  /// Enables or disables PRE of scalars in GVN.
  GVNOptions &setScalarPRE(bool ScalarPRE) {
    AllowScalarPRE = ScalarPRE;
    return *this;
  }
 
  /// Enables or disables PRE of loads in GVN.
  GVNOptions &setLoadPRE(bool LoadPRE) {
    AllowLoadPRE = LoadPRE;
    return *this;
  }
 
  GVNOptions &setLoadInLoopPRE(bool LoadInLoopPRE) {
    AllowLoadInLoopPRE = LoadInLoopPRE;
    return *this;
  }
 
  /// Enables or disables PRE of loads in GVN.
  GVNOptions &setLoadPRESplitBackedge(bool LoadPRESplitBackedge) {
    AllowLoadPRESplitBackedge = LoadPRESplitBackedge;
    return *this;
  }
 
  /// Enables or disables use of MemDepAnalysis.
  GVNOptions &setMemDep(bool MemDep) {
    AllowMemDep = MemDep;
    return *this;
  }
 
  /// Enables or disables use of MemorySSA.
  GVNOptions &setMemorySSA(bool MemSSA) {
    AllowMemorySSA = MemSSA;
    return *this;
  }
};
 
class GVNPass : public OptionalPassInfoMixin<GVNPass> {
  std::unique_ptr<GVNPassImpl> Impl;
 
public:
  LLVM_ABI GVNPass(GVNOptions Options = {});
  LLVM_ABI ~GVNPass();
 
  LLVM_ABI GVNPass(GVNPass &&) noexcept;
  LLVM_ABI GVNPass &operator=(GVNPass &&) noexcept;
 
  GVNPass(const GVNPass &) = delete;
  GVNPass &operator=(const GVNPass &) = delete;
 
  /// Run the pass over the function.
  LLVM_ABI PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
 
  LLVM_ABI void
  printPipeline(raw_ostream &OS,
                function_ref<StringRef(StringRef)> MapClassName2PassName);
};
 
/// Create a legacy GVN pass.
LLVM_ABI FunctionPass *createGVNPass(bool ScalarPRE);
LLVM_ABI FunctionPass *createGVNPass();
 
} // end namespace llvm
 
#endif // LLVM_TRANSFORMS_SCALAR_GVN_H