1 //=- llvm/CodeGen/AntiDepBreaker.h - Anti-Dependence Breaking -*- C++ -*-=//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements the AntiDepBreaker class, which implements
11 // anti-dependence breaking heuristics for post-register-allocation scheduling.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_LIB_CODEGEN_ANTIDEPBREAKER_H
16 #define LLVM_LIB_CODEGEN_ANTIDEPBREAKER_H
17 
18 #include "llvm/CodeGen/MachineBasicBlock.h"
19 #include "llvm/CodeGen/MachineFrameInfo.h"
20 #include "llvm/CodeGen/MachineFunction.h"
21 #include "llvm/CodeGen/MachineRegisterInfo.h"
22 #include "llvm/CodeGen/ScheduleDAG.h"
23 #include "llvm/Target/TargetRegisterInfo.h"
24 #include <vector>
25 
26 namespace llvm {
27 
28 /// This class works in conjunction with the post-RA scheduler to rename
29 /// registers to break register anti-dependencies (WAR hazards).
30 class AntiDepBreaker {
31 public:
32   typedef std::vector<std::pair<MachineInstr *, MachineInstr *> >
33     DbgValueVector;
34 
35   virtual ~AntiDepBreaker();
36 
37   /// Initialize anti-dep breaking for a new basic block.
38   virtual void StartBlock(MachineBasicBlock *BB) =0;
39 
40   /// Identifiy anti-dependencies within a basic-block region and break them by
41   /// renaming registers. Return the number of anti-dependencies broken.
42   virtual unsigned BreakAntiDependencies(const std::vector<SUnit>& SUnits,
43                                          MachineBasicBlock::iterator Begin,
44                                          MachineBasicBlock::iterator End,
45                                          unsigned InsertPosIndex,
46                                          DbgValueVector &DbgValues) = 0;
47 
48   /// Update liveness information to account for the current
49   /// instruction, which will not be scheduled.
50   virtual void Observe(MachineInstr *MI, unsigned Count,
51                        unsigned InsertPosIndex) =0;
52 
53   /// Finish anti-dep breaking for a basic block.
54   virtual void FinishBlock() =0;
55 
56   /// Update DBG_VALUE if dependency breaker is updating
57   /// other machine instruction to use NewReg.
UpdateDbgValue(MachineInstr * MI,unsigned OldReg,unsigned NewReg)58   void UpdateDbgValue(MachineInstr *MI, unsigned OldReg, unsigned NewReg) {
59     assert (MI->isDebugValue() && "MI is not DBG_VALUE!");
60     if (MI && MI->getOperand(0).isReg() && MI->getOperand(0).getReg() == OldReg)
61       MI->getOperand(0).setReg(NewReg);
62   }
63 };
64 
65 }
66 
67 #endif
68