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
template<typename T> class SSAUpdaterTraits;
27
class BumpPtrAllocator;
29
/// MachineSSAUpdater - This class updates SSA form for a set of virtual
30
/// registers defined in multiple blocks. This is used when code duplication
31
/// or another unstructured transformation wants to rewrite a set of uses of one
32
/// vreg with uses of a set of vregs.
33
class MachineSSAUpdater {
34
friend class SSAUpdaterTraits<MachineSSAUpdater>;
37
/// AvailableVals - This keeps track of which value to use on a per-block
38
/// basis. When we insert PHI nodes, we keep track of them here.
39
//typedef DenseMap<MachineBasicBlock*, unsigned > AvailableValsTy;
42
/// VR - Current virtual register whose uses are being updated.
45
/// VRC - Register class of the current virtual register.
46
const TargetRegisterClass *VRC;
48
/// InsertedPHIs - If this is non-null, the MachineSSAUpdater adds all PHI
49
/// nodes that it creates to the vector.
50
SmallVectorImpl<MachineInstr*> *InsertedPHIs;
52
const TargetInstrInfo *TII;
53
MachineRegisterInfo *MRI;
55
/// MachineSSAUpdater constructor. If InsertedPHIs is specified, it will be
56
/// filled in with all PHI Nodes created by rewriting.
57
explicit MachineSSAUpdater(MachineFunction &MF,
58
SmallVectorImpl<MachineInstr*> *InsertedPHIs = 0);
61
/// Initialize - Reset this object to get ready for a new set of SSA
63
void Initialize(unsigned V);
65
/// AddAvailableValue - Indicate that a rewritten value is available at the
66
/// end of the specified block with the specified value.
67
void AddAvailableValue(MachineBasicBlock *BB, unsigned V);
69
/// HasValueForBlock - Return true if the MachineSSAUpdater already has a
70
/// value for the specified block.
71
bool HasValueForBlock(MachineBasicBlock *BB) const;
73
/// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
74
/// live at the end of the specified block.
75
unsigned GetValueAtEndOfBlock(MachineBasicBlock *BB);
77
/// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
78
/// is live in the middle of the specified block.
80
/// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one
81
/// important case: if there is a definition of the rewritten value after the
82
/// 'use' in BB. Consider code like this:
88
/// br Cond, SomeBB, OutBB
90
/// In this case, there are two values (X1 and X2) added to the AvailableVals
91
/// set by the client of the rewriter, and those values are both live out of
92
/// their respective blocks. However, the use of X happens in the *middle* of
93
/// a block. Because of this, we need to insert a new PHI node in SomeBB to
94
/// merge the appropriate values, and this value isn't live out of the block.
96
unsigned GetValueInMiddleOfBlock(MachineBasicBlock *BB);
98
/// RewriteUse - Rewrite a use of the symbolic value. This handles PHI nodes,
99
/// which use their value in the corresponding predecessor. Note that this
100
/// will not work if the use is supposed to be rewritten to a value defined in
101
/// the same block as the use, but above it. Any 'AddAvailableValue's added
102
/// for the use's block will be considered to be below it.
103
void RewriteUse(MachineOperand &U);
106
void ReplaceRegWith(unsigned OldReg, unsigned NewReg);
107
unsigned GetValueAtEndOfBlockInternal(MachineBasicBlock *BB);
109
void operator=(const MachineSSAUpdater&); // DO NOT IMPLEMENT
110
MachineSSAUpdater(const MachineSSAUpdater&); // DO NOT IMPLEMENT
113
} // End llvm namespace