1 //===-- SimpleRegisterCoalescing.h - Register Coalescing --------*- 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 implements a simple register copy coalescing phase.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_CODEGEN_SIMPLE_REGISTER_COALESCING_H
15 #define LLVM_CODEGEN_SIMPLE_REGISTER_COALESCING_H
17 #include "llvm/CodeGen/MachineFunctionPass.h"
18 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
19 #include "llvm/CodeGen/RegisterCoalescer.h"
20 #include "llvm/ADT/BitVector.h"
23 class SimpleRegisterCoalescing;
24 class LiveDebugVariables;
25 class TargetRegisterInfo;
26 class TargetInstrInfo;
28 class MachineLoopInfo;
30 /// CopyRec - Representation for copy instructions in coalescer queue.
35 CopyRec(MachineInstr *mi, unsigned depth)
36 : MI(mi), LoopDepth(depth) {}
39 class SimpleRegisterCoalescing : public MachineFunctionPass,
40 public RegisterCoalescer {
42 MachineRegisterInfo* mri_;
43 const TargetMachine* tm_;
44 const TargetRegisterInfo* tri_;
45 const TargetInstrInfo* tii_;
47 LiveDebugVariables *ldv_;
48 const MachineLoopInfo* loopInfo;
51 DenseMap<const TargetRegisterClass*, BitVector> allocatableRCRegs_;
53 /// JoinedCopies - Keep track of copies eliminated due to coalescing.
55 SmallPtrSet<MachineInstr*, 32> JoinedCopies;
57 /// ReMatCopies - Keep track of copies eliminated due to remat.
59 SmallPtrSet<MachineInstr*, 32> ReMatCopies;
61 /// ReMatDefs - Keep track of definition instructions which have
63 SmallPtrSet<MachineInstr*, 8> ReMatDefs;
66 static char ID; // Pass identifcation, replacement for typeid
67 SimpleRegisterCoalescing() : MachineFunctionPass(ID) {
68 initializeSimpleRegisterCoalescingPass(*PassRegistry::getPassRegistry());
81 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
82 virtual void releaseMemory();
84 /// runOnMachineFunction - pass entry point
85 virtual bool runOnMachineFunction(MachineFunction&);
87 bool coalesceFunction(MachineFunction &mf, RegallocQuery &) {
88 // This runs as an independent pass, so don't do anything.
92 /// print - Implement the dump method.
93 virtual void print(raw_ostream &O, const Module* = 0) const;
96 /// joinIntervals - join compatible live intervals
99 /// CopyCoalesceInMBB - Coalesce copies in the specified MBB, putting
100 /// copies that cannot yet be coalesced into the "TryAgain" list.
101 void CopyCoalesceInMBB(MachineBasicBlock *MBB,
102 std::vector<CopyRec> &TryAgain);
104 /// JoinCopy - Attempt to join intervals corresponding to SrcReg/DstReg,
105 /// which are the src/dst of the copy instruction CopyMI. This returns true
106 /// if the copy was successfully coalesced away. If it is not currently
107 /// possible to coalesce this interval, but it may be possible if other
108 /// things get coalesced, then it returns true by reference in 'Again'.
109 bool JoinCopy(CopyRec &TheCopy, bool &Again);
111 /// JoinIntervals - Attempt to join these two intervals. On failure, this
112 /// returns false. The output "SrcInt" will not have been modified, so we can
113 /// use this information below to update aliases.
114 bool JoinIntervals(CoalescerPair &CP);
116 /// Return true if the two specified registers belong to different register
117 /// classes. The registers may be either phys or virt regs.
118 bool differingRegisterClasses(unsigned RegA, unsigned RegB) const;
120 /// AdjustCopiesBackFrom - We found a non-trivially-coalescable copy. If
121 /// the source value number is defined by a copy from the destination reg
122 /// see if we can merge these two destination reg valno# into a single
123 /// value number, eliminating a copy.
124 bool AdjustCopiesBackFrom(const CoalescerPair &CP, MachineInstr *CopyMI);
126 /// HasOtherReachingDefs - Return true if there are definitions of IntB
127 /// other than BValNo val# that can reach uses of AValno val# of IntA.
128 bool HasOtherReachingDefs(LiveInterval &IntA, LiveInterval &IntB,
129 VNInfo *AValNo, VNInfo *BValNo);
131 /// RemoveCopyByCommutingDef - We found a non-trivially-coalescable copy.
132 /// If the source value number is defined by a commutable instruction and
133 /// its other operand is coalesced to the copy dest register, see if we
134 /// can transform the copy into a noop by commuting the definition.
135 bool RemoveCopyByCommutingDef(const CoalescerPair &CP,MachineInstr *CopyMI);
137 /// TrimLiveIntervalToLastUse - If there is a last use in the same basic
138 /// block as the copy instruction, trim the ive interval to the last use
140 bool TrimLiveIntervalToLastUse(SlotIndex CopyIdx,
141 MachineBasicBlock *CopyMBB,
142 LiveInterval &li, const LiveRange *LR);
144 /// ReMaterializeTrivialDef - If the source of a copy is defined by a trivial
145 /// computation, replace the copy by rematerialize the definition.
146 bool ReMaterializeTrivialDef(LiveInterval &SrcInt, unsigned DstReg,
147 unsigned DstSubIdx, MachineInstr *CopyMI);
149 /// isWinToJoinCrossClass - Return true if it's profitable to coalesce
150 /// two virtual registers from different register classes.
151 bool isWinToJoinCrossClass(unsigned SrcReg,
153 const TargetRegisterClass *SrcRC,
154 const TargetRegisterClass *DstRC,
155 const TargetRegisterClass *NewRC);
157 /// UpdateRegDefsUses - Replace all defs and uses of SrcReg to DstReg and
158 /// update the subregister number if it is not zero. If DstReg is a
159 /// physical register and the existing subregister number of the def / use
160 /// being updated is not zero, make sure to set it to the correct physical
162 void UpdateRegDefsUses(const CoalescerPair &CP);
164 /// ShortenDeadCopyLiveRange - Shorten a live range defined by a dead copy.
165 /// Return true if live interval is removed.
166 bool ShortenDeadCopyLiveRange(LiveInterval &li, MachineInstr *CopyMI);
168 /// ShortenDeadCopyLiveRange - Shorten a live range as it's artificially
169 /// extended by a dead copy. Mark the last use (if any) of the val# as kill
170 /// as ends the live range there. If there isn't another use, then this
171 /// live range is dead. Return true if live interval is removed.
172 bool ShortenDeadCopySrcLiveRange(LiveInterval &li, MachineInstr *CopyMI);
174 /// RemoveDeadDef - If a def of a live interval is now determined dead,
175 /// remove the val# it defines. If the live interval becomes empty, remove
177 bool RemoveDeadDef(LiveInterval &li, MachineInstr *DefMI);
179 /// RemoveCopyFlag - If DstReg is no longer defined by CopyMI, clear the
180 /// VNInfo copy flag for DstReg and all aliases.
181 void RemoveCopyFlag(unsigned DstReg, const MachineInstr *CopyMI);
183 /// lastRegisterUse - Returns the last use of the specific register between
184 /// cycles Start and End or NULL if there are no uses.
185 MachineOperand *lastRegisterUse(SlotIndex Start, SlotIndex End,
186 unsigned Reg, SlotIndex &LastUseIdx) const;
189 } // End llvm namespace