1 //===-- MachineSSAUpdater.h - Unstructured SSA Update Tool ------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file declares the MachineSSAUpdater class.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_CODEGEN_MACHINESSAUPDATER_H
15 #define LLVM_CODEGEN_MACHINESSAUPDATER_H
18 class MachineBasicBlock;
19 class MachineFunction;
22 class MachineRegisterInfo;
23 class TargetInstrInfo;
24 class TargetRegisterClass;
25 template<typename T> class SmallVectorImpl;
26 class BumpPtrAllocator;
28 /// MachineSSAUpdater - This class updates SSA form for a set of virtual
29 /// registers defined in multiple blocks. This is used when code duplication
30 /// or another unstructured transformation wants to rewrite a set of uses of one
31 /// vreg with uses of a set of vregs.
32 class MachineSSAUpdater {
35 typedef SmallVectorImpl<BBInfo*> BlockListTy;
38 /// AvailableVals - This keeps track of which value to use on a per-block
39 /// basis. When we insert PHI nodes, we keep track of them here.
40 //typedef DenseMap<MachineBasicBlock*, unsigned > AvailableValsTy;
43 /// BBMap - The GetValueAtEndOfBlock method maintains this mapping from
44 /// basic blocks to BBInfo structures.
45 /// typedef DenseMap<MachineBasicBlock*, BBInfo*> BBMapTy;
48 /// VR - Current virtual register whose uses are being updated.
51 /// VRC - Register class of the current virtual register.
52 const TargetRegisterClass *VRC;
54 /// InsertedPHIs - If this is non-null, the MachineSSAUpdater adds all PHI
55 /// nodes that it creates to the vector.
56 SmallVectorImpl<MachineInstr*> *InsertedPHIs;
58 const TargetInstrInfo *TII;
59 MachineRegisterInfo *MRI;
61 /// MachineSSAUpdater constructor. If InsertedPHIs is specified, it will be
62 /// filled in with all PHI Nodes created by rewriting.
63 explicit MachineSSAUpdater(MachineFunction &MF,
64 SmallVectorImpl<MachineInstr*> *InsertedPHIs = 0);
67 /// Initialize - Reset this object to get ready for a new set of SSA
69 void Initialize(unsigned V);
71 /// AddAvailableValue - Indicate that a rewritten value is available at the
72 /// end of the specified block with the specified value.
73 void AddAvailableValue(MachineBasicBlock *BB, unsigned V);
75 /// HasValueForBlock - Return true if the MachineSSAUpdater already has a
76 /// value for the specified block.
77 bool HasValueForBlock(MachineBasicBlock *BB) const;
79 /// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
80 /// live at the end of the specified block.
81 unsigned GetValueAtEndOfBlock(MachineBasicBlock *BB);
83 /// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
84 /// is live in the middle of the specified block.
86 /// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one
87 /// important case: if there is a definition of the rewritten value after the
88 /// 'use' in BB. Consider code like this:
94 /// br Cond, SomeBB, OutBB
96 /// In this case, there are two values (X1 and X2) added to the AvailableVals
97 /// set by the client of the rewriter, and those values are both live out of
98 /// their respective blocks. However, the use of X happens in the *middle* of
99 /// a block. Because of this, we need to insert a new PHI node in SomeBB to
100 /// merge the appropriate values, and this value isn't live out of the block.
102 unsigned GetValueInMiddleOfBlock(MachineBasicBlock *BB);
104 /// RewriteUse - Rewrite a use of the symbolic value. This handles PHI nodes,
105 /// which use their value in the corresponding predecessor. Note that this
106 /// will not work if the use is supposed to be rewritten to a value defined in
107 /// the same block as the use, but above it. Any 'AddAvailableValue's added
108 /// for the use's block will be considered to be below it.
109 void RewriteUse(MachineOperand &U);
112 void ReplaceRegWith(unsigned OldReg, unsigned NewReg);
113 unsigned GetValueAtEndOfBlockInternal(MachineBasicBlock *BB);
114 void BuildBlockList(MachineBasicBlock *BB, BlockListTy *BlockList,
115 BumpPtrAllocator *Allocator);
116 void FindDominators(BlockListTy *BlockList);
117 void FindPHIPlacement(BlockListTy *BlockList);
118 void FindAvailableVals(BlockListTy *BlockList);
119 void FindExistingPHI(MachineBasicBlock *BB, BlockListTy *BlockList);
120 bool CheckIfPHIMatches(MachineInstr *PHI);
121 void RecordMatchingPHI(MachineInstr *PHI);
123 void operator=(const MachineSSAUpdater&); // DO NOT IMPLEMENT
124 MachineSSAUpdater(const MachineSSAUpdater&); // DO NOT IMPLEMENT
127 } // End llvm namespace