1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
|
//=- llvm/CodeGen/ScheduleHazardRecognizer.h - Scheduling Support -*- C++ -*-=//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the ScheduleHazardRecognizer class, which implements
// hazard-avoidance heuristics for scheduling.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_SCHEDULEHAZARDRECOGNIZER_H
#define LLVM_CODEGEN_SCHEDULEHAZARDRECOGNIZER_H
namespace llvm {
class SUnit;
/// HazardRecognizer - This determines whether or not an instruction can be
/// issued this cycle, and whether or not a noop needs to be inserted to handle
/// the hazard.
class ScheduleHazardRecognizer {
protected:
/// MaxLookAhead - Indicate the number of cycles in the scoreboard
/// state. Important to restore the state after backtracking. Additionally,
/// MaxLookAhead=0 identifies a fake recognizer, allowing the client to
/// bypass virtual calls. Currently the PostRA scheduler ignores it.
unsigned MaxLookAhead;
public:
ScheduleHazardRecognizer(): MaxLookAhead(0) {}
virtual ~ScheduleHazardRecognizer();
enum HazardType {
NoHazard, // This instruction can be emitted at this cycle.
Hazard, // This instruction can't be emitted at this cycle.
NoopHazard // This instruction can't be emitted, and needs noops.
};
unsigned getMaxLookAhead() const { return MaxLookAhead; }
bool isEnabled() const { return MaxLookAhead != 0; }
/// atIssueLimit - Return true if no more instructions may be issued in this
/// cycle.
///
/// FIXME: remove this once MachineScheduler is the only client.
virtual bool atIssueLimit() const { return false; }
/// getHazardType - Return the hazard type of emitting this node. There are
/// three possible results. Either:
/// * NoHazard: it is legal to issue this instruction on this cycle.
/// * Hazard: issuing this instruction would stall the machine. If some
/// other instruction is available, issue it first.
/// * NoopHazard: issuing this instruction would break the program. If
/// some other instruction can be issued, do so, otherwise issue a noop.
virtual HazardType getHazardType(SUnit *m, int Stalls = 0) {
return NoHazard;
}
/// Reset - This callback is invoked when a new block of
/// instructions is about to be schedule. The hazard state should be
/// set to an initialized state.
virtual void Reset() {}
/// EmitInstruction - This callback is invoked when an instruction is
/// emitted, to advance the hazard state.
virtual void EmitInstruction(SUnit *) {}
/// AdvanceCycle - This callback is invoked whenever the next top-down
/// instruction to be scheduled cannot issue in the current cycle, either
/// because of latency or resource conflicts. This should increment the
/// internal state of the hazard recognizer so that previously "Hazard"
/// instructions will now not be hazards.
virtual void AdvanceCycle() {}
/// RecedeCycle - This callback is invoked whenever the next bottom-up
/// instruction to be scheduled cannot issue in the current cycle, either
/// because of latency or resource conflicts.
virtual void RecedeCycle() {}
/// EmitNoop - This callback is invoked when a noop was added to the
/// instruction stream.
virtual void EmitNoop() {
// Default implementation: count it as a cycle.
AdvanceCycle();
}
};
}
#endif
|
