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thirdparty/capstone/suite/synctools/tablegen/include/llvm/CodeGen/MachineSSAUpdater.h

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+//===- MachineSSAUpdater.h - Unstructured SSA Update Tool -------*- 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 file declares the MachineSSAUpdater class.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_MACHINESSAUPDATER_H
+#define LLVM_CODEGEN_MACHINESSAUPDATER_H
+
+#include "llvm/CodeGen/Register.h"
+
+namespace llvm {
+
+class MachineBasicBlock;
+class MachineFunction;
+class MachineInstr;
+class MachineOperand;
+class MachineRegisterInfo;
+class TargetInstrInfo;
+class TargetRegisterClass;
+template<typename T> class SmallVectorImpl;
+template<typename T> class SSAUpdaterTraits;
+
+/// MachineSSAUpdater - This class updates SSA form for a set of virtual
+/// registers defined in multiple blocks.  This is used when code duplication
+/// or another unstructured transformation wants to rewrite a set of uses of one
+/// vreg with uses of a set of vregs.
+class MachineSSAUpdater {
+  friend class SSAUpdaterTraits<MachineSSAUpdater>;
+
+private:
+  /// AvailableVals - This keeps track of which value to use on a per-block
+  /// basis.  When we insert PHI nodes, we keep track of them here.
+  //typedef DenseMap<MachineBasicBlock*, Register> AvailableValsTy;
+  void *AV = nullptr;
+
+  /// VRC - Register class of the current virtual register.
+  const TargetRegisterClass *VRC;
+
+  /// InsertedPHIs - If this is non-null, the MachineSSAUpdater adds all PHI
+  /// nodes that it creates to the vector.
+  SmallVectorImpl<MachineInstr*> *InsertedPHIs;
+
+  const TargetInstrInfo *TII;
+  MachineRegisterInfo *MRI;
+
+public:
+  /// MachineSSAUpdater constructor.  If InsertedPHIs is specified, it will be
+  /// filled in with all PHI Nodes created by rewriting.
+  explicit MachineSSAUpdater(MachineFunction &MF,
+                        SmallVectorImpl<MachineInstr*> *NewPHI = nullptr);
+  MachineSSAUpdater(const MachineSSAUpdater &) = delete;
+  MachineSSAUpdater &operator=(const MachineSSAUpdater &) = delete;
+  ~MachineSSAUpdater();
+
+  /// Initialize - Reset this object to get ready for a new set of SSA
+  /// updates.
+  void Initialize(Register V);
+  void Initialize(const TargetRegisterClass *RC);
+
+  /// AddAvailableValue - Indicate that a rewritten value is available at the
+  /// end of the specified block with the specified value.
+  void AddAvailableValue(MachineBasicBlock *BB, Register V);
+
+  /// HasValueForBlock - Return true if the MachineSSAUpdater already has a
+  /// value for the specified block.
+  bool HasValueForBlock(MachineBasicBlock *BB) const;
+
+  /// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
+  /// live at the end of the specified block.
+  Register GetValueAtEndOfBlock(MachineBasicBlock *BB);
+
+  /// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
+  /// is live in the middle of the specified block. If ExistingValueOnly is
+  /// true then this will only return an existing value or $noreg; otherwise new
+  /// instructions may be inserted to materialize a value.
+  ///
+  /// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one
+  /// important case: if there is a definition of the rewritten value after the
+  /// 'use' in BB.  Consider code like this:
+  ///
+  ///      X1 = ...
+  ///   SomeBB:
+  ///      use(X)
+  ///      X2 = ...
+  ///      br Cond, SomeBB, OutBB
+  ///
+  /// In this case, there are two values (X1 and X2) added to the AvailableVals
+  /// set by the client of the rewriter, and those values are both live out of
+  /// their respective blocks.  However, the use of X happens in the *middle* of
+  /// a block.  Because of this, we need to insert a new PHI node in SomeBB to
+  /// merge the appropriate values, and this value isn't live out of the block.
+  Register GetValueInMiddleOfBlock(MachineBasicBlock *BB,
+                                   bool ExistingValueOnly = false);
+
+  /// RewriteUse - Rewrite a use of the symbolic value.  This handles PHI nodes,
+  /// which use their value in the corresponding predecessor.  Note that this
+  /// will not work if the use is supposed to be rewritten to a value defined in
+  /// the same block as the use, but above it.  Any 'AddAvailableValue's added
+  /// for the use's block will be considered to be below it.
+  void RewriteUse(MachineOperand &U);
+
+private:
+  // If ExistingValueOnly is true, will not create any new instructions. Used
+  // for debug values, which cannot modify Codegen.
+  Register GetValueAtEndOfBlockInternal(MachineBasicBlock *BB,
+                                        bool ExistingValueOnly = false);
+};
+
+} // end namespace llvm
+
+#endif // LLVM_CODEGEN_MACHINESSAUPDATER_H