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
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
|
#pragma once
#ifdef __GNUC__
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-parameter"
#endif
//===- lib/CodeGen/CalcSpillWeights.h ---------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_CALCSPILLWEIGHTS_H
#define LLVM_CODEGEN_CALCSPILLWEIGHTS_H
#include "llvm/ADT/DenseMap.h"
#include "llvm/CodeGen/SlotIndexes.h"
namespace llvm {
class LiveInterval;
class LiveIntervals;
class MachineBlockFrequencyInfo;
class MachineFunction;
class MachineLoopInfo;
class VirtRegMap;
/// Normalize the spill weight of a live interval
///
/// The spill weight of a live interval is computed as:
///
/// (sum(use freq) + sum(def freq)) / (K + size)
///
/// @param UseDefFreq Expected number of executed use and def instructions
/// per function call. Derived from block frequencies.
/// @param Size Size of live interval as returnexd by getSize()
/// @param NumInstr Number of instructions using this live interval
static inline float normalizeSpillWeight(float UseDefFreq, unsigned Size,
unsigned NumInstr) {
// The constant 25 instructions is added to avoid depending too much on
// accidental SlotIndex gaps for small intervals. The effect is that small
// intervals have a spill weight that is mostly proportional to the number
// of uses, while large intervals get a spill weight that is closer to a use
// density.
return UseDefFreq / (Size + 25*SlotIndex::InstrDist);
}
/// Calculate auxiliary information for a virtual register such as its
/// spill weight and allocation hint.
class VirtRegAuxInfo {
MachineFunction &MF;
LiveIntervals &LIS;
const VirtRegMap &VRM;
const MachineLoopInfo &Loops;
const MachineBlockFrequencyInfo &MBFI;
/// Returns true if Reg of live interval LI is used in instruction with many
/// operands like STATEPOINT.
bool isLiveAtStatepointVarArg(LiveInterval &LI);
public:
VirtRegAuxInfo(MachineFunction &MF, LiveIntervals &LIS,
const VirtRegMap &VRM, const MachineLoopInfo &Loops,
const MachineBlockFrequencyInfo &MBFI)
: MF(MF), LIS(LIS), VRM(VRM), Loops(Loops), MBFI(MBFI) {}
virtual ~VirtRegAuxInfo() = default;
/// (re)compute li's spill weight and allocation hint.
void calculateSpillWeightAndHint(LiveInterval &LI);
/// Compute future expected spill weight of a split artifact of LI
/// that will span between start and end slot indexes.
/// \param LI The live interval to be split.
/// \param Start The expected beginning of the split artifact. Instructions
/// before start will not affect the weight.
/// \param End The expected end of the split artifact. Instructions
/// after end will not affect the weight.
/// \return The expected spill weight of the split artifact. Returns
/// negative weight for unspillable LI.
float futureWeight(LiveInterval &LI, SlotIndex Start, SlotIndex End);
/// Compute spill weights and allocation hints for all virtual register
/// live intervals.
void calculateSpillWeightsAndHints();
/// Return the preferred allocation register for reg, given a COPY
/// instruction.
static Register copyHint(const MachineInstr *MI, unsigned Reg,
const TargetRegisterInfo &TRI,
const MachineRegisterInfo &MRI);
/// Determine if all values in LI are rematerializable.
static bool isRematerializable(const LiveInterval &LI,
const LiveIntervals &LIS,
const VirtRegMap &VRM,
const TargetInstrInfo &TII);
protected:
/// Helper function for weight calculations.
/// (Re)compute LI's spill weight and allocation hint, or, for non null
/// start and end - compute future expected spill weight of a split
/// artifact of LI that will span between start and end slot indexes.
/// \param LI The live interval for which to compute the weight.
/// \param Start The expected beginning of the split artifact. Instructions
/// before start will not affect the weight. Relevant for
/// weight calculation of future split artifact.
/// \param End The expected end of the split artifact. Instructions
/// after end will not affect the weight. Relevant for
/// weight calculation of future split artifact.
/// \return The spill weight. Returns negative weight for unspillable LI.
float weightCalcHelper(LiveInterval &LI, SlotIndex *Start = nullptr,
SlotIndex *End = nullptr);
/// Weight normalization function.
virtual float normalize(float UseDefFreq, unsigned Size,
unsigned NumInstr) {
return normalizeSpillWeight(UseDefFreq, Size, NumInstr);
}
};
} // end namespace llvm
#endif // LLVM_CODEGEN_CALCSPILLWEIGHTS_H
#ifdef __GNUC__
#pragma GCC diagnostic pop
#endif
|
