1 //===-- PowerPCSubtarget.cpp - PPC Subtarget Information ------------------===//
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 PPC specific subclass of TargetSubtargetInfo.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "PPCSubtarget.h"
14 #include "GISel/PPCCallLowering.h"
15 #include "GISel/PPCLegalizerInfo.h"
16 #include "GISel/PPCRegisterBankInfo.h"
17 #include "PPC.h"
18 #include "PPCRegisterInfo.h"
19 #include "PPCTargetMachine.h"
20 #include "llvm/CodeGen/GlobalISel/InstructionSelect.h"
21 #include "llvm/CodeGen/GlobalISel/InstructionSelector.h"
22 #include "llvm/CodeGen/MachineFunction.h"
23 #include "llvm/CodeGen/MachineScheduler.h"
24 #include "llvm/IR/Attributes.h"
25 #include "llvm/IR/Function.h"
26 #include "llvm/IR/GlobalAlias.h"
27 #include "llvm/IR/GlobalValue.h"
28 #include "llvm/IR/GlobalVariable.h"
29 #include "llvm/MC/TargetRegistry.h"
30 #include "llvm/Support/CommandLine.h"
31 #include "llvm/Target/TargetMachine.h"
32 #include <cstdlib>
33
34 using namespace llvm;
35
36 #define DEBUG_TYPE "ppc-subtarget"
37
38 #define GET_SUBTARGETINFO_TARGET_DESC
39 #define GET_SUBTARGETINFO_CTOR
40 #include "PPCGenSubtargetInfo.inc"
41
42 static cl::opt<bool>
43 EnableMachinePipeliner("ppc-enable-pipeliner",
44 cl::desc("Enable Machine Pipeliner for PPC"),
45 cl::init(false), cl::Hidden);
46
initializeSubtargetDependencies(StringRef CPU,StringRef TuneCPU,StringRef FS)47 PPCSubtarget &PPCSubtarget::initializeSubtargetDependencies(StringRef CPU,
48 StringRef TuneCPU,
49 StringRef FS) {
50 initializeEnvironment();
51 initSubtargetFeatures(CPU, TuneCPU, FS);
52 return *this;
53 }
54
PPCSubtarget(const Triple & TT,const std::string & CPU,const std::string & TuneCPU,const std::string & FS,const PPCTargetMachine & TM)55 PPCSubtarget::PPCSubtarget(const Triple &TT, const std::string &CPU,
56 const std::string &TuneCPU, const std::string &FS,
57 const PPCTargetMachine &TM)
58 : PPCGenSubtargetInfo(TT, CPU, TuneCPU, FS), TargetTriple(TT),
59 IsPPC64(TargetTriple.getArch() == Triple::ppc64 ||
60 TargetTriple.getArch() == Triple::ppc64le),
61 TM(TM), FrameLowering(initializeSubtargetDependencies(CPU, TuneCPU, FS)),
62 InstrInfo(*this), TLInfo(TM, *this) {
63 CallLoweringInfo.reset(new PPCCallLowering(*getTargetLowering()));
64 Legalizer.reset(new PPCLegalizerInfo(*this));
65 auto *RBI = new PPCRegisterBankInfo(*getRegisterInfo());
66 RegBankInfo.reset(RBI);
67
68 InstSelector.reset(createPPCInstructionSelector(TM, *this, *RBI));
69 }
70
initializeEnvironment()71 void PPCSubtarget::initializeEnvironment() {
72 StackAlignment = Align(16);
73 CPUDirective = PPC::DIR_NONE;
74 HasPOPCNTD = POPCNTD_Unavailable;
75 }
76
initSubtargetFeatures(StringRef CPU,StringRef TuneCPU,StringRef FS)77 void PPCSubtarget::initSubtargetFeatures(StringRef CPU, StringRef TuneCPU,
78 StringRef FS) {
79 // Determine default and user specified characteristics
80 std::string CPUName = std::string(CPU);
81 if (CPUName.empty() || CPU == "generic") {
82 // If cross-compiling with -march=ppc64le without -mcpu
83 if (TargetTriple.getArch() == Triple::ppc64le)
84 CPUName = "ppc64le";
85 else if (TargetTriple.getSubArch() == Triple::PPCSubArch_spe)
86 CPUName = "e500";
87 else
88 CPUName = "generic";
89 }
90
91 // Determine the CPU to schedule for.
92 if (TuneCPU.empty()) TuneCPU = CPUName;
93
94 // Initialize scheduling itinerary for the specified CPU.
95 InstrItins = getInstrItineraryForCPU(CPUName);
96
97 // Parse features string.
98 ParseSubtargetFeatures(CPUName, TuneCPU, FS);
99
100 // If the user requested use of 64-bit regs, but the cpu selected doesn't
101 // support it, ignore.
102 if (IsPPC64 && has64BitSupport())
103 Use64BitRegs = true;
104
105 if (TargetTriple.isPPC32SecurePlt())
106 IsSecurePlt = true;
107
108 if (HasSPE && IsPPC64)
109 report_fatal_error( "SPE is only supported for 32-bit targets.\n", false);
110 if (HasSPE && (HasAltivec || HasVSX || HasFPU))
111 report_fatal_error(
112 "SPE and traditional floating point cannot both be enabled.\n", false);
113
114 // If not SPE, set standard FPU
115 if (!HasSPE)
116 HasFPU = true;
117
118 StackAlignment = getPlatformStackAlignment();
119
120 // Determine endianness.
121 IsLittleEndian = TM.isLittleEndian();
122
123 if (HasAIXSmallLocalExecTLS || HasAIXSmallLocalDynamicTLS) {
124 if (!TargetTriple.isOSAIX() || !IsPPC64)
125 report_fatal_error("The aix-small-local-[exec|dynamic]-tls attribute is "
126 "only supported on AIX in "
127 "64-bit mode.\n",
128 false);
129 // The aix-small-local-[exec|dynamic]-tls attribute should only be used with
130 // -data-sections, as having data sections turned off with this option
131 // is not ideal for performance. Moreover, the
132 // small-local-[exec|dynamic]-tls region is a limited resource, and should
133 // not be used for variables that may be replaced.
134 if (!TM.getDataSections())
135 report_fatal_error("The aix-small-local-[exec|dynamic]-tls attribute can "
136 "only be specified with "
137 "-data-sections.\n",
138 false);
139 }
140
141 if (HasAIXShLibTLSModelOpt && (!TargetTriple.isOSAIX() || !IsPPC64))
142 report_fatal_error("The aix-shared-lib-tls-model-opt attribute "
143 "is only supported on AIX in 64-bit mode.\n",
144 false);
145 }
146
enableMachineScheduler() const147 bool PPCSubtarget::enableMachineScheduler() const { return true; }
148
enableMachinePipeliner() const149 bool PPCSubtarget::enableMachinePipeliner() const {
150 return getSchedModel().hasInstrSchedModel() && EnableMachinePipeliner;
151 }
152
useDFAforSMS() const153 bool PPCSubtarget::useDFAforSMS() const { return false; }
154
155 // This overrides the PostRAScheduler bit in the SchedModel for each CPU.
enablePostRAScheduler() const156 bool PPCSubtarget::enablePostRAScheduler() const { return true; }
157
getAntiDepBreakMode() const158 PPCGenSubtargetInfo::AntiDepBreakMode PPCSubtarget::getAntiDepBreakMode() const {
159 return TargetSubtargetInfo::ANTIDEP_ALL;
160 }
161
getCriticalPathRCs(RegClassVector & CriticalPathRCs) const162 void PPCSubtarget::getCriticalPathRCs(RegClassVector &CriticalPathRCs) const {
163 CriticalPathRCs.clear();
164 CriticalPathRCs.push_back(isPPC64() ?
165 &PPC::G8RCRegClass : &PPC::GPRCRegClass);
166 }
167
overrideSchedPolicy(MachineSchedPolicy & Policy,unsigned NumRegionInstrs) const168 void PPCSubtarget::overrideSchedPolicy(MachineSchedPolicy &Policy,
169 unsigned NumRegionInstrs) const {
170 // The GenericScheduler that we use defaults to scheduling bottom up only.
171 // We want to schedule from both the top and the bottom and so we set
172 // OnlyBottomUp to false.
173 // We want to do bi-directional scheduling since it provides a more balanced
174 // schedule leading to better performance.
175 Policy.OnlyBottomUp = false;
176 // Spilling is generally expensive on all PPC cores, so always enable
177 // register-pressure tracking.
178 Policy.ShouldTrackPressure = true;
179 }
180
useAA() const181 bool PPCSubtarget::useAA() const {
182 return true;
183 }
184
enableSubRegLiveness() const185 bool PPCSubtarget::enableSubRegLiveness() const { return true; }
186
isGVIndirectSymbol(const GlobalValue * GV) const187 bool PPCSubtarget::isGVIndirectSymbol(const GlobalValue *GV) const {
188 if (isAIXABI()) {
189 if (const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV))
190 // On AIX the only symbols that aren't indirect are toc-data.
191 return !GVar->hasAttribute("toc-data");
192
193 return true;
194 }
195
196 // Large code model always uses the TOC even for local symbols.
197 if (TM.getCodeModel() == CodeModel::Large)
198 return true;
199
200 if (TM.shouldAssumeDSOLocal(GV))
201 return false;
202 return true;
203 }
204
getCodeModel(const TargetMachine & TM,const GlobalValue * GV) const205 CodeModel::Model PPCSubtarget::getCodeModel(const TargetMachine &TM,
206 const GlobalValue *GV) const {
207 // If there isn't an attribute to override the module code model
208 // this will be the effective code model.
209 CodeModel::Model ModuleModel = TM.getCodeModel();
210
211 // Initially support per global code model for AIX only.
212 if (!isAIXABI())
213 return ModuleModel;
214
215 // Only GlobalVariables carry an attribute which can override the module code
216 // model.
217 assert(GV && "Unexpected NULL GlobalValue");
218 const GlobalVariable *GlobalVar =
219 [](const GlobalValue *GV) -> const GlobalVariable * {
220 const GlobalVariable *Var = dyn_cast<GlobalVariable>(GV);
221 if (Var)
222 return Var;
223
224 const GlobalAlias *Alias = dyn_cast<GlobalAlias>(GV);
225 if (Alias)
226 return dyn_cast<GlobalVariable>(Alias->getAliaseeObject());
227
228 return nullptr;
229 }(GV);
230
231 if (!GlobalVar)
232 return ModuleModel;
233
234 std::optional<CodeModel::Model> MaybeCodeModel = GlobalVar->getCodeModel();
235 if (MaybeCodeModel) {
236 CodeModel::Model CM = *MaybeCodeModel;
237 assert((CM == CodeModel::Small || CM == CodeModel::Large) &&
238 "invalid code model for AIX");
239 return CM;
240 }
241
242 return ModuleModel;
243 }
244
isELFv2ABI() const245 bool PPCSubtarget::isELFv2ABI() const { return TM.isELFv2ABI(); }
isPPC64() const246 bool PPCSubtarget::isPPC64() const { return TM.isPPC64(); }
247
isUsingPCRelativeCalls() const248 bool PPCSubtarget::isUsingPCRelativeCalls() const {
249 return isPPC64() && hasPCRelativeMemops() && isELFv2ABI() &&
250 CodeModel::Medium == getTargetMachine().getCodeModel();
251 }
252
253 // GlobalISEL
getCallLowering() const254 const CallLowering *PPCSubtarget::getCallLowering() const {
255 return CallLoweringInfo.get();
256 }
257
getRegBankInfo() const258 const RegisterBankInfo *PPCSubtarget::getRegBankInfo() const {
259 return RegBankInfo.get();
260 }
261
getLegalizerInfo() const262 const LegalizerInfo *PPCSubtarget::getLegalizerInfo() const {
263 return Legalizer.get();
264 }
265
getInstructionSelector() const266 InstructionSelector *PPCSubtarget::getInstructionSelector() const {
267 return InstSelector.get();
268 }
269