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
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
|
//===---- ARM64StorePairSuppress.cpp --- Suppress store pair formation ----===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass identifies floating point stores that should not be combined into
// store pairs. Later we may do the same for floating point loads.
// ===---------------------------------------------------------------------===//
#include "ARM64InstrInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineTraceMetrics.h"
#include "llvm/CodeGen/TargetSchedule.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
using namespace llvm;
#define DEBUG_TYPE "arm64-stp-suppress"
namespace {
class ARM64StorePairSuppress : public MachineFunctionPass {
const ARM64InstrInfo *TII;
const TargetRegisterInfo *TRI;
const MachineRegisterInfo *MRI;
MachineFunction *MF;
TargetSchedModel SchedModel;
MachineTraceMetrics *Traces;
MachineTraceMetrics::Ensemble *MinInstr;
public:
static char ID;
ARM64StorePairSuppress() : MachineFunctionPass(ID) {}
virtual const char *getPassName() const override {
return "ARM64 Store Pair Suppression";
}
bool runOnMachineFunction(MachineFunction &F) override;
private:
bool shouldAddSTPToBlock(const MachineBasicBlock *BB);
bool isNarrowFPStore(const MachineInstr &MI);
virtual void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
AU.addRequired<MachineTraceMetrics>();
AU.addPreserved<MachineTraceMetrics>();
MachineFunctionPass::getAnalysisUsage(AU);
}
};
char ARM64StorePairSuppress::ID = 0;
} // anonymous
FunctionPass *llvm::createARM64StorePairSuppressPass() {
return new ARM64StorePairSuppress();
}
/// Return true if an STP can be added to this block without increasing the
/// critical resource height. STP is good to form in Ld/St limited blocks and
/// bad to form in float-point limited blocks. This is true independent of the
/// critical path. If the critical path is longer than the resource height, the
/// extra vector ops can limit physreg renaming. Otherwise, it could simply
/// oversaturate the vector units.
bool ARM64StorePairSuppress::shouldAddSTPToBlock(const MachineBasicBlock *BB) {
if (!MinInstr)
MinInstr = Traces->getEnsemble(MachineTraceMetrics::TS_MinInstrCount);
MachineTraceMetrics::Trace BBTrace = MinInstr->getTrace(BB);
unsigned ResLength = BBTrace.getResourceLength();
// Get the machine model's scheduling class for STPQi.
// Bypass TargetSchedule's SchedClass resolution since we only have an opcode.
unsigned SCIdx = TII->get(ARM64::STPDi).getSchedClass();
const MCSchedClassDesc *SCDesc =
SchedModel.getMCSchedModel()->getSchedClassDesc(SCIdx);
// If a subtarget does not define resources for STPQi, bail here.
if (SCDesc->isValid() && !SCDesc->isVariant()) {
unsigned ResLenWithSTP = BBTrace.getResourceLength(
ArrayRef<const MachineBasicBlock *>(), SCDesc);
if (ResLenWithSTP > ResLength) {
DEBUG(dbgs() << " Suppress STP in BB: " << BB->getNumber()
<< " resources " << ResLength << " -> " << ResLenWithSTP
<< "\n");
return false;
}
}
return true;
}
/// Return true if this is a floating-point store smaller than the V reg. On
/// cyclone, these require a vector shuffle before storing a pair.
/// Ideally we would call getMatchingPairOpcode() and have the machine model
/// tell us if it's profitable with no cpu knowledge here.
///
/// FIXME: We plan to develop a decent Target abstraction for simple loads and
/// stores. Until then use a nasty switch similar to ARM64LoadStoreOptimizer.
bool ARM64StorePairSuppress::isNarrowFPStore(const MachineInstr &MI) {
switch (MI.getOpcode()) {
default:
return false;
case ARM64::STRSui:
case ARM64::STRDui:
case ARM64::STURSi:
case ARM64::STURDi:
return true;
}
}
bool ARM64StorePairSuppress::runOnMachineFunction(MachineFunction &mf) {
MF = &mf;
TII = static_cast<const ARM64InstrInfo *>(MF->getTarget().getInstrInfo());
TRI = MF->getTarget().getRegisterInfo();
MRI = &MF->getRegInfo();
const TargetSubtargetInfo &ST =
MF->getTarget().getSubtarget<TargetSubtargetInfo>();
SchedModel.init(*ST.getSchedModel(), &ST, TII);
Traces = &getAnalysis<MachineTraceMetrics>();
MinInstr = nullptr;
DEBUG(dbgs() << "*** " << getPassName() << ": " << MF->getName() << '\n');
if (!SchedModel.hasInstrSchedModel()) {
DEBUG(dbgs() << " Skipping pass: no machine model present.\n");
return false;
}
// Check for a sequence of stores to the same base address. We don't need to
// precisely determine whether a store pair can be formed. But we do want to
// filter out most situations where we can't form store pairs to avoid
// computing trace metrics in those cases.
for (auto &MBB : *MF) {
bool SuppressSTP = false;
unsigned PrevBaseReg = 0;
for (auto &MI : MBB) {
if (!isNarrowFPStore(MI))
continue;
unsigned BaseReg;
unsigned Offset;
if (TII->getLdStBaseRegImmOfs(&MI, BaseReg, Offset, TRI)) {
if (PrevBaseReg == BaseReg) {
// If this block can take STPs, skip ahead to the next block.
if (!SuppressSTP && shouldAddSTPToBlock(MI.getParent()))
break;
// Otherwise, continue unpairing the stores in this block.
DEBUG(dbgs() << "Unpairing store " << MI << "\n");
SuppressSTP = true;
TII->suppressLdStPair(&MI);
}
PrevBaseReg = BaseReg;
} else
PrevBaseReg = 0;
}
}
// This pass just sets some internal MachineMemOperand flags. It can't really
// invalidate anything.
return false;
}
|
