Subversion Repositories QNX 8.QNX8 LLVM/Clang compiler suite

Rev

Details | Last modification | View Log | RSS feed

Rev Author Line No. Line
14 pmbaty 1
//===- llvm/CodeGen/AntiDepBreaker.h - Anti-Dependence Breaking -*- C++ -*-===//
2
//
3
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4
// See https://llvm.org/LICENSE.txt for license information.
5
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6
//
7
//===----------------------------------------------------------------------===//
8
//
9
// This file implements the AntiDepBreaker class, which implements
10
// anti-dependence breaking heuristics for post-register-allocation scheduling.
11
//
12
//===----------------------------------------------------------------------===//
13
 
14
#ifndef LLVM_CODEGEN_ANTIDEPBREAKER_H
15
#define LLVM_CODEGEN_ANTIDEPBREAKER_H
16
 
17
#include "llvm/ADT/iterator_range.h"
18
#include "llvm/CodeGen/MachineBasicBlock.h"
19
#include "llvm/CodeGen/MachineInstr.h"
20
#include "llvm/CodeGen/TargetSubtargetInfo.h"
21
#include "llvm/Support/Compiler.h"
22
#include <cassert>
23
#include <utility>
24
#include <vector>
25
 
26
namespace llvm {
27
 
28
class RegisterClassInfo;
29
 
30
/// This class works in conjunction with the post-RA scheduler to rename
31
/// registers to break register anti-dependencies (WAR hazards).
32
class AntiDepBreaker {
33
public:
34
  using DbgValueVector =
35
      std::vector<std::pair<MachineInstr *, MachineInstr *>>;
36
 
37
  virtual ~AntiDepBreaker();
38
 
39
  /// Initialize anti-dep breaking for a new basic block.
40
  virtual void StartBlock(MachineBasicBlock *BB) = 0;
41
 
42
  /// Identifiy anti-dependencies within a basic-block region and break them by
43
  /// renaming registers. Return the number of anti-dependencies broken.
44
  virtual unsigned BreakAntiDependencies(const std::vector<SUnit> &SUnits,
45
                                         MachineBasicBlock::iterator Begin,
46
                                         MachineBasicBlock::iterator End,
47
                                         unsigned InsertPosIndex,
48
                                         DbgValueVector &DbgValues) = 0;
49
 
50
  /// Update liveness information to account for the current
51
  /// instruction, which will not be scheduled.
52
  virtual void Observe(MachineInstr &MI, unsigned Count,
53
                       unsigned InsertPosIndex) = 0;
54
 
55
  /// Finish anti-dep breaking for a basic block.
56
  virtual void FinishBlock() = 0;
57
 
58
  /// Update DBG_VALUE or DBG_PHI if dependency breaker is updating
59
  /// other machine instruction to use NewReg.
60
  void UpdateDbgValue(MachineInstr &MI, unsigned OldReg, unsigned NewReg) {
61
    if (MI.isDebugValue()) {
62
      if (MI.getDebugOperand(0).isReg() &&
63
          MI.getDebugOperand(0).getReg() == OldReg)
64
        MI.getDebugOperand(0).setReg(NewReg);
65
    } else if (MI.isDebugPHI()) {
66
      if (MI.getOperand(0).isReg() &&
67
          MI.getOperand(0).getReg() == OldReg)
68
        MI.getOperand(0).setReg(NewReg);
69
    } else {
70
      llvm_unreachable("MI is not DBG_VALUE / DBG_PHI!");
71
    }
72
  }
73
 
74
  /// Update all DBG_VALUE instructions that may be affected by the dependency
75
  /// breaker's update of ParentMI to use NewReg.
76
  void UpdateDbgValues(const DbgValueVector &DbgValues, MachineInstr *ParentMI,
77
                       unsigned OldReg, unsigned NewReg) {
78
    // The following code is dependent on the order in which the DbgValues are
79
    // constructed in ScheduleDAGInstrs::buildSchedGraph.
80
    MachineInstr *PrevDbgMI = nullptr;
81
    for (const auto &DV : make_range(DbgValues.crbegin(), DbgValues.crend())) {
82
      MachineInstr *PrevMI = DV.second;
83
      if ((PrevMI == ParentMI) || (PrevMI == PrevDbgMI)) {
84
        MachineInstr *DbgMI = DV.first;
85
        UpdateDbgValue(*DbgMI, OldReg, NewReg);
86
        PrevDbgMI = DbgMI;
87
      } else if (PrevDbgMI) {
88
        break; // If no match and already found a DBG_VALUE, we're done.
89
      }
90
    }
91
  }
92
};
93
 
94
AntiDepBreaker *createAggressiveAntiDepBreaker(
95
    MachineFunction &MFi, const RegisterClassInfo &RCI,
96
    TargetSubtargetInfo::RegClassVector &CriticalPathRCs);
97
 
98
AntiDepBreaker *createCriticalAntiDepBreaker(MachineFunction &MFi,
99
                                             const RegisterClassInfo &RCI);
100
 
101
} // end namespace llvm
102
 
103
#endif // LLVM_CODEGEN_ANTIDEPBREAKER_H