1 //===-- AArch64Subtarget.cpp - AArch64 Subtarget Information ----*- 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 AArch64 specific subclass of TargetSubtarget.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "AArch64Subtarget.h"
14
15 #include "AArch64.h"
16 #include "AArch64CallLowering.h"
17 #include "AArch64InstrInfo.h"
18 #include "AArch64LegalizerInfo.h"
19 #include "AArch64PBQPRegAlloc.h"
20 #include "AArch64RegisterBankInfo.h"
21 #include "AArch64TargetMachine.h"
22 #include "MCTargetDesc/AArch64AddressingModes.h"
23 #include "llvm/CodeGen/GlobalISel/InstructionSelect.h"
24 #include "llvm/CodeGen/MachineScheduler.h"
25 #include "llvm/IR/GlobalValue.h"
26 #include "llvm/Support/TargetParser.h"
27
28 using namespace llvm;
29
30 #define DEBUG_TYPE "aarch64-subtarget"
31
32 #define GET_SUBTARGETINFO_CTOR
33 #define GET_SUBTARGETINFO_TARGET_DESC
34 #include "AArch64GenSubtargetInfo.inc"
35
36 static cl::opt<bool>
37 EnableEarlyIfConvert("aarch64-early-ifcvt", cl::desc("Enable the early if "
38 "converter pass"), cl::init(true), cl::Hidden);
39
40 // If OS supports TBI, use this flag to enable it.
41 static cl::opt<bool>
42 UseAddressTopByteIgnored("aarch64-use-tbi", cl::desc("Assume that top byte of "
43 "an address is ignored"), cl::init(false), cl::Hidden);
44
45 static cl::opt<bool>
46 UseNonLazyBind("aarch64-enable-nonlazybind",
47 cl::desc("Call nonlazybind functions via direct GOT load"),
48 cl::init(false), cl::Hidden);
49
50 AArch64Subtarget &
initializeSubtargetDependencies(StringRef FS,StringRef CPUString)51 AArch64Subtarget::initializeSubtargetDependencies(StringRef FS,
52 StringRef CPUString) {
53 // Determine default and user-specified characteristics
54
55 if (CPUString.empty())
56 CPUString = "generic";
57
58 ParseSubtargetFeatures(CPUString, FS);
59 initializeProperties();
60
61 return *this;
62 }
63
initializeProperties()64 void AArch64Subtarget::initializeProperties() {
65 // Initialize CPU specific properties. We should add a tablegen feature for
66 // this in the future so we can specify it together with the subtarget
67 // features.
68 switch (ARMProcFamily) {
69 case Others:
70 break;
71 case CortexA35:
72 break;
73 case CortexA53:
74 PrefFunctionLogAlignment = 3;
75 break;
76 case CortexA55:
77 break;
78 case CortexA57:
79 MaxInterleaveFactor = 4;
80 PrefFunctionLogAlignment = 4;
81 break;
82 case CortexA65:
83 PrefFunctionLogAlignment = 3;
84 break;
85 case CortexA72:
86 case CortexA73:
87 case CortexA75:
88 case CortexA76:
89 PrefFunctionLogAlignment = 4;
90 break;
91 case AppleA7:
92 case AppleA10:
93 case AppleA11:
94 case AppleA12:
95 case AppleA13:
96 CacheLineSize = 64;
97 PrefetchDistance = 280;
98 MinPrefetchStride = 2048;
99 MaxPrefetchIterationsAhead = 3;
100 break;
101 case ExynosM3:
102 MaxInterleaveFactor = 4;
103 MaxJumpTableSize = 20;
104 PrefFunctionLogAlignment = 5;
105 PrefLoopLogAlignment = 4;
106 break;
107 case Falkor:
108 MaxInterleaveFactor = 4;
109 // FIXME: remove this to enable 64-bit SLP if performance looks good.
110 MinVectorRegisterBitWidth = 128;
111 CacheLineSize = 128;
112 PrefetchDistance = 820;
113 MinPrefetchStride = 2048;
114 MaxPrefetchIterationsAhead = 8;
115 break;
116 case Kryo:
117 MaxInterleaveFactor = 4;
118 VectorInsertExtractBaseCost = 2;
119 CacheLineSize = 128;
120 PrefetchDistance = 740;
121 MinPrefetchStride = 1024;
122 MaxPrefetchIterationsAhead = 11;
123 // FIXME: remove this to enable 64-bit SLP if performance looks good.
124 MinVectorRegisterBitWidth = 128;
125 break;
126 case NeoverseE1:
127 PrefFunctionLogAlignment = 3;
128 break;
129 case NeoverseN1:
130 PrefFunctionLogAlignment = 4;
131 break;
132 case Saphira:
133 MaxInterleaveFactor = 4;
134 // FIXME: remove this to enable 64-bit SLP if performance looks good.
135 MinVectorRegisterBitWidth = 128;
136 break;
137 case ThunderX2T99:
138 CacheLineSize = 64;
139 PrefFunctionLogAlignment = 3;
140 PrefLoopLogAlignment = 2;
141 MaxInterleaveFactor = 4;
142 PrefetchDistance = 128;
143 MinPrefetchStride = 1024;
144 MaxPrefetchIterationsAhead = 4;
145 // FIXME: remove this to enable 64-bit SLP if performance looks good.
146 MinVectorRegisterBitWidth = 128;
147 break;
148 case ThunderX:
149 case ThunderXT88:
150 case ThunderXT81:
151 case ThunderXT83:
152 CacheLineSize = 128;
153 PrefFunctionLogAlignment = 3;
154 PrefLoopLogAlignment = 2;
155 // FIXME: remove this to enable 64-bit SLP if performance looks good.
156 MinVectorRegisterBitWidth = 128;
157 break;
158 case TSV110:
159 CacheLineSize = 64;
160 PrefFunctionLogAlignment = 4;
161 PrefLoopLogAlignment = 2;
162 break;
163 }
164 }
165
AArch64Subtarget(const Triple & TT,const std::string & CPU,const std::string & FS,const TargetMachine & TM,bool LittleEndian)166 AArch64Subtarget::AArch64Subtarget(const Triple &TT, const std::string &CPU,
167 const std::string &FS,
168 const TargetMachine &TM, bool LittleEndian)
169 : AArch64GenSubtargetInfo(TT, CPU, FS),
170 ReserveXRegister(AArch64::GPR64commonRegClass.getNumRegs()),
171 CustomCallSavedXRegs(AArch64::GPR64commonRegClass.getNumRegs()),
172 IsLittle(LittleEndian),
173 TargetTriple(TT), FrameLowering(),
174 InstrInfo(initializeSubtargetDependencies(FS, CPU)), TSInfo(),
175 TLInfo(TM, *this) {
176 if (AArch64::isX18ReservedByDefault(TT))
177 ReserveXRegister.set(18);
178
179 CallLoweringInfo.reset(new AArch64CallLowering(*getTargetLowering()));
180 Legalizer.reset(new AArch64LegalizerInfo(*this));
181
182 auto *RBI = new AArch64RegisterBankInfo(*getRegisterInfo());
183
184 // FIXME: At this point, we can't rely on Subtarget having RBI.
185 // It's awkward to mix passing RBI and the Subtarget; should we pass
186 // TII/TRI as well?
187 InstSelector.reset(createAArch64InstructionSelector(
188 *static_cast<const AArch64TargetMachine *>(&TM), *this, *RBI));
189
190 RegBankInfo.reset(RBI);
191 }
192
getCallLowering() const193 const CallLowering *AArch64Subtarget::getCallLowering() const {
194 return CallLoweringInfo.get();
195 }
196
getInstructionSelector() const197 InstructionSelector *AArch64Subtarget::getInstructionSelector() const {
198 return InstSelector.get();
199 }
200
getLegalizerInfo() const201 const LegalizerInfo *AArch64Subtarget::getLegalizerInfo() const {
202 return Legalizer.get();
203 }
204
getRegBankInfo() const205 const RegisterBankInfo *AArch64Subtarget::getRegBankInfo() const {
206 return RegBankInfo.get();
207 }
208
209 /// Find the target operand flags that describe how a global value should be
210 /// referenced for the current subtarget.
211 unsigned
ClassifyGlobalReference(const GlobalValue * GV,const TargetMachine & TM) const212 AArch64Subtarget::ClassifyGlobalReference(const GlobalValue *GV,
213 const TargetMachine &TM) const {
214 // MachO large model always goes via a GOT, simply to get a single 8-byte
215 // absolute relocation on all global addresses.
216 if (TM.getCodeModel() == CodeModel::Large && isTargetMachO())
217 return AArch64II::MO_GOT;
218
219 if (!TM.shouldAssumeDSOLocal(*GV->getParent(), GV)) {
220 if (GV->hasDLLImportStorageClass())
221 return AArch64II::MO_GOT | AArch64II::MO_DLLIMPORT;
222 if (getTargetTriple().isOSWindows())
223 return AArch64II::MO_GOT | AArch64II::MO_COFFSTUB;
224 return AArch64II::MO_GOT;
225 }
226
227 // The small code model's direct accesses use ADRP, which cannot
228 // necessarily produce the value 0 (if the code is above 4GB).
229 // Same for the tiny code model, where we have a pc relative LDR.
230 if ((useSmallAddressing() || TM.getCodeModel() == CodeModel::Tiny) &&
231 GV->hasExternalWeakLinkage())
232 return AArch64II::MO_GOT;
233
234 // References to tagged globals are marked with MO_NC | MO_TAGGED to indicate
235 // that their nominal addresses are tagged and outside of the code model. In
236 // AArch64ExpandPseudo::expandMI we emit an additional instruction to set the
237 // tag if necessary based on MO_TAGGED.
238 if (AllowTaggedGlobals && !isa<FunctionType>(GV->getValueType()))
239 return AArch64II::MO_NC | AArch64II::MO_TAGGED;
240
241 return AArch64II::MO_NO_FLAG;
242 }
243
classifyGlobalFunctionReference(const GlobalValue * GV,const TargetMachine & TM) const244 unsigned AArch64Subtarget::classifyGlobalFunctionReference(
245 const GlobalValue *GV, const TargetMachine &TM) const {
246 // MachO large model always goes via a GOT, because we don't have the
247 // relocations available to do anything else..
248 if (TM.getCodeModel() == CodeModel::Large && isTargetMachO() &&
249 !GV->hasInternalLinkage())
250 return AArch64II::MO_GOT;
251
252 // NonLazyBind goes via GOT unless we know it's available locally.
253 auto *F = dyn_cast<Function>(GV);
254 if (UseNonLazyBind && F && F->hasFnAttribute(Attribute::NonLazyBind) &&
255 !TM.shouldAssumeDSOLocal(*GV->getParent(), GV))
256 return AArch64II::MO_GOT;
257
258 // Use ClassifyGlobalReference for setting MO_DLLIMPORT/MO_COFFSTUB.
259 if (getTargetTriple().isOSWindows())
260 return ClassifyGlobalReference(GV, TM);
261
262 return AArch64II::MO_NO_FLAG;
263 }
264
overrideSchedPolicy(MachineSchedPolicy & Policy,unsigned NumRegionInstrs) const265 void AArch64Subtarget::overrideSchedPolicy(MachineSchedPolicy &Policy,
266 unsigned NumRegionInstrs) const {
267 // LNT run (at least on Cyclone) showed reasonably significant gains for
268 // bi-directional scheduling. 253.perlbmk.
269 Policy.OnlyTopDown = false;
270 Policy.OnlyBottomUp = false;
271 // Enabling or Disabling the latency heuristic is a close call: It seems to
272 // help nearly no benchmark on out-of-order architectures, on the other hand
273 // it regresses register pressure on a few benchmarking.
274 Policy.DisableLatencyHeuristic = DisableLatencySchedHeuristic;
275 }
276
enableEarlyIfConversion() const277 bool AArch64Subtarget::enableEarlyIfConversion() const {
278 return EnableEarlyIfConvert;
279 }
280
supportsAddressTopByteIgnored() const281 bool AArch64Subtarget::supportsAddressTopByteIgnored() const {
282 if (!UseAddressTopByteIgnored)
283 return false;
284
285 if (TargetTriple.isiOS()) {
286 unsigned Major, Minor, Micro;
287 TargetTriple.getiOSVersion(Major, Minor, Micro);
288 return Major >= 8;
289 }
290
291 return false;
292 }
293
294 std::unique_ptr<PBQPRAConstraint>
getCustomPBQPConstraints() const295 AArch64Subtarget::getCustomPBQPConstraints() const {
296 return balanceFPOps() ? std::make_unique<A57ChainingConstraint>() : nullptr;
297 }
298
mirFileLoaded(MachineFunction & MF) const299 void AArch64Subtarget::mirFileLoaded(MachineFunction &MF) const {
300 // We usually compute max call frame size after ISel. Do the computation now
301 // if the .mir file didn't specify it. Note that this will probably give you
302 // bogus values after PEI has eliminated the callframe setup/destroy pseudo
303 // instructions, specify explicitly if you need it to be correct.
304 MachineFrameInfo &MFI = MF.getFrameInfo();
305 if (!MFI.isMaxCallFrameSizeComputed())
306 MFI.computeMaxCallFrameSize(MF);
307 }
308