113 lines
4.3 KiB
C++
113 lines
4.3 KiB
C++
//===- MachineSSAUpdater.h - Unstructured SSA Update Tool -------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file declares the MachineSSAUpdater class.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CODEGEN_MACHINESSAUPDATER_H
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#define LLVM_CODEGEN_MACHINESSAUPDATER_H
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#include "llvm/CodeGen/Register.h"
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namespace llvm {
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class MachineBasicBlock;
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class MachineFunction;
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class MachineInstr;
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class MachineOperand;
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class MachineRegisterInfo;
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class TargetInstrInfo;
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class TargetRegisterClass;
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template<typename T> class SmallVectorImpl;
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template<typename T> class SSAUpdaterTraits;
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/// MachineSSAUpdater - This class updates SSA form for a set of virtual
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/// registers defined in multiple blocks. This is used when code duplication
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/// or another unstructured transformation wants to rewrite a set of uses of one
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/// vreg with uses of a set of vregs.
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class MachineSSAUpdater {
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friend class SSAUpdaterTraits<MachineSSAUpdater>;
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private:
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/// AvailableVals - This keeps track of which value to use on a per-block
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/// basis. When we insert PHI nodes, we keep track of them here.
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//typedef DenseMap<MachineBasicBlock*, Register> AvailableValsTy;
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void *AV = nullptr;
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/// VRC - Register class of the current virtual register.
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const TargetRegisterClass *VRC;
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/// InsertedPHIs - If this is non-null, the MachineSSAUpdater adds all PHI
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/// nodes that it creates to the vector.
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SmallVectorImpl<MachineInstr*> *InsertedPHIs;
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const TargetInstrInfo *TII;
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MachineRegisterInfo *MRI;
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public:
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/// MachineSSAUpdater constructor. If InsertedPHIs is specified, it will be
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/// filled in with all PHI Nodes created by rewriting.
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explicit MachineSSAUpdater(MachineFunction &MF,
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SmallVectorImpl<MachineInstr*> *NewPHI = nullptr);
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MachineSSAUpdater(const MachineSSAUpdater &) = delete;
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MachineSSAUpdater &operator=(const MachineSSAUpdater &) = delete;
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~MachineSSAUpdater();
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/// Initialize - Reset this object to get ready for a new set of SSA
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/// updates.
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void Initialize(Register V);
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void Initialize(const TargetRegisterClass *RC);
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/// AddAvailableValue - Indicate that a rewritten value is available at the
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/// end of the specified block with the specified value.
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void AddAvailableValue(MachineBasicBlock *BB, Register V);
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/// HasValueForBlock - Return true if the MachineSSAUpdater already has a
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/// value for the specified block.
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bool HasValueForBlock(MachineBasicBlock *BB) const;
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/// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
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/// live at the end of the specified block.
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Register GetValueAtEndOfBlock(MachineBasicBlock *BB);
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/// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
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/// is live in the middle of the specified block.
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///
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/// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one
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/// important case: if there is a definition of the rewritten value after the
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/// 'use' in BB. Consider code like this:
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///
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/// X1 = ...
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/// SomeBB:
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/// use(X)
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/// X2 = ...
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/// br Cond, SomeBB, OutBB
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///
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/// In this case, there are two values (X1 and X2) added to the AvailableVals
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/// set by the client of the rewriter, and those values are both live out of
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/// their respective blocks. However, the use of X happens in the *middle* of
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/// a block. Because of this, we need to insert a new PHI node in SomeBB to
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/// merge the appropriate values, and this value isn't live out of the block.
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Register GetValueInMiddleOfBlock(MachineBasicBlock *BB);
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/// RewriteUse - Rewrite a use of the symbolic value. This handles PHI nodes,
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/// which use their value in the corresponding predecessor. Note that this
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/// will not work if the use is supposed to be rewritten to a value defined in
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/// the same block as the use, but above it. Any 'AddAvailableValue's added
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/// for the use's block will be considered to be below it.
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void RewriteUse(MachineOperand &U);
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private:
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Register GetValueAtEndOfBlockInternal(MachineBasicBlock *BB);
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};
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} // end namespace llvm
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#endif // LLVM_CODEGEN_MACHINESSAUPDATER_H
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