1 //===-- ARMTargetMachine.cpp - Define TargetMachine for ARM ---------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "ARMTargetMachine.h"
14 #include "ARM.h"
15 #include "ARMMacroFusion.h"
16 #include "ARMSubtarget.h"
17 #include "ARMTargetObjectFile.h"
18 #include "ARMTargetTransformInfo.h"
19 #include "MCTargetDesc/ARMMCTargetDesc.h"
20 #include "llvm/ADT/Optional.h"
21 #include "llvm/ADT/STLExtras.h"
22 #include "llvm/ADT/StringRef.h"
23 #include "llvm/ADT/Triple.h"
24 #include "llvm/Analysis/TargetTransformInfo.h"
25 #include "llvm/CodeGen/ExecutionDomainFix.h"
26 #include "llvm/CodeGen/GlobalISel/CallLowering.h"
27 #include "llvm/CodeGen/GlobalISel/IRTranslator.h"
28 #include "llvm/CodeGen/GlobalISel/InstructionSelect.h"
29 #include "llvm/CodeGen/GlobalISel/InstructionSelector.h"
30 #include "llvm/CodeGen/GlobalISel/Legalizer.h"
31 #include "llvm/CodeGen/GlobalISel/LegalizerInfo.h"
32 #include "llvm/CodeGen/GlobalISel/RegBankSelect.h"
33 #include "llvm/CodeGen/GlobalISel/RegisterBankInfo.h"
34 #include "llvm/CodeGen/MachineFunction.h"
35 #include "llvm/CodeGen/MachineScheduler.h"
36 #include "llvm/CodeGen/Passes.h"
37 #include "llvm/CodeGen/TargetPassConfig.h"
38 #include "llvm/IR/Attributes.h"
39 #include "llvm/IR/DataLayout.h"
40 #include "llvm/IR/Function.h"
41 #include "llvm/Pass.h"
42 #include "llvm/Support/CodeGen.h"
43 #include "llvm/Support/CommandLine.h"
44 #include "llvm/Support/ErrorHandling.h"
45 #include "llvm/Support/TargetParser.h"
46 #include "llvm/Support/TargetRegistry.h"
47 #include "llvm/Target/TargetLoweringObjectFile.h"
48 #include "llvm/Target/TargetOptions.h"
49 #include "llvm/Transforms/Scalar.h"
50 #include <cassert>
51 #include <memory>
52 #include <string>
53 
54 using namespace llvm;
55 
56 static cl::opt<bool>
57 DisableA15SDOptimization("disable-a15-sd-optimization", cl::Hidden,
58                    cl::desc("Inhibit optimization of S->D register accesses on A15"),
59                    cl::init(false));
60 
61 static cl::opt<bool>
62 EnableAtomicTidy("arm-atomic-cfg-tidy", cl::Hidden,
63                  cl::desc("Run SimplifyCFG after expanding atomic operations"
64                           " to make use of cmpxchg flow-based information"),
65                  cl::init(true));
66 
67 static cl::opt<bool>
68 EnableARMLoadStoreOpt("arm-load-store-opt", cl::Hidden,
69                       cl::desc("Enable ARM load/store optimization pass"),
70                       cl::init(true));
71 
72 // FIXME: Unify control over GlobalMerge.
73 static cl::opt<cl::boolOrDefault>
74 EnableGlobalMerge("arm-global-merge", cl::Hidden,
75                   cl::desc("Enable the global merge pass"));
76 
77 namespace llvm {
78   void initializeARMExecutionDomainFixPass(PassRegistry&);
79 }
80 
81 extern "C" void LLVMInitializeARMTarget() {
82   // Register the target.
83   RegisterTargetMachine<ARMLETargetMachine> X(getTheARMLETarget());
84   RegisterTargetMachine<ARMLETargetMachine> A(getTheThumbLETarget());
85   RegisterTargetMachine<ARMBETargetMachine> Y(getTheARMBETarget());
86   RegisterTargetMachine<ARMBETargetMachine> B(getTheThumbBETarget());
87 
88   PassRegistry &Registry = *PassRegistry::getPassRegistry();
89   initializeGlobalISel(Registry);
90   initializeARMLoadStoreOptPass(Registry);
91   initializeARMPreAllocLoadStoreOptPass(Registry);
92   initializeARMConstantIslandsPass(Registry);
93   initializeARMExecutionDomainFixPass(Registry);
94   initializeARMExpandPseudoPass(Registry);
95   initializeThumb2SizeReducePass(Registry);
96 }
97 
98 static std::unique_ptr<TargetLoweringObjectFile> createTLOF(const Triple &TT) {
99   if (TT.isOSBinFormatMachO())
100     return llvm::make_unique<TargetLoweringObjectFileMachO>();
101   if (TT.isOSWindows())
102     return llvm::make_unique<TargetLoweringObjectFileCOFF>();
103   return llvm::make_unique<ARMElfTargetObjectFile>();
104 }
105 
106 static ARMBaseTargetMachine::ARMABI
107 computeTargetABI(const Triple &TT, StringRef CPU,
108                  const TargetOptions &Options) {
109   StringRef ABIName = Options.MCOptions.getABIName();
110 
111   if (ABIName.empty())
112     ABIName = ARM::computeDefaultTargetABI(TT, CPU);
113 
114   if (ABIName == "aapcs16")
115     return ARMBaseTargetMachine::ARM_ABI_AAPCS16;
116   else if (ABIName.startswith("aapcs"))
117     return ARMBaseTargetMachine::ARM_ABI_AAPCS;
118   else if (ABIName.startswith("apcs"))
119     return ARMBaseTargetMachine::ARM_ABI_APCS;
120 
121   llvm_unreachable("Unhandled/unknown ABI Name!");
122   return ARMBaseTargetMachine::ARM_ABI_UNKNOWN;
123 }
124 
125 static std::string computeDataLayout(const Triple &TT, StringRef CPU,
126                                      const TargetOptions &Options,
127                                      bool isLittle) {
128   auto ABI = computeTargetABI(TT, CPU, Options);
129   std::string Ret;
130 
131   if (isLittle)
132     // Little endian.
133     Ret += "e";
134   else
135     // Big endian.
136     Ret += "E";
137 
138   Ret += DataLayout::getManglingComponent(TT);
139 
140   // Pointers are 32 bits and aligned to 32 bits.
141   Ret += "-p:32:32";
142 
143   // ABIs other than APCS have 64 bit integers with natural alignment.
144   if (ABI != ARMBaseTargetMachine::ARM_ABI_APCS)
145     Ret += "-i64:64";
146 
147   // We have 64 bits floats. The APCS ABI requires them to be aligned to 32
148   // bits, others to 64 bits. We always try to align to 64 bits.
149   if (ABI == ARMBaseTargetMachine::ARM_ABI_APCS)
150     Ret += "-f64:32:64";
151 
152   // We have 128 and 64 bit vectors. The APCS ABI aligns them to 32 bits, others
153   // to 64. We always ty to give them natural alignment.
154   if (ABI == ARMBaseTargetMachine::ARM_ABI_APCS)
155     Ret += "-v64:32:64-v128:32:128";
156   else if (ABI != ARMBaseTargetMachine::ARM_ABI_AAPCS16)
157     Ret += "-v128:64:128";
158 
159   // Try to align aggregates to 32 bits (the default is 64 bits, which has no
160   // particular hardware support on 32-bit ARM).
161   Ret += "-a:0:32";
162 
163   // Integer registers are 32 bits.
164   Ret += "-n32";
165 
166   // The stack is 128 bit aligned on NaCl, 64 bit aligned on AAPCS and 32 bit
167   // aligned everywhere else.
168   if (TT.isOSNaCl() || ABI == ARMBaseTargetMachine::ARM_ABI_AAPCS16)
169     Ret += "-S128";
170   else if (ABI == ARMBaseTargetMachine::ARM_ABI_AAPCS)
171     Ret += "-S64";
172   else
173     Ret += "-S32";
174 
175   return Ret;
176 }
177 
178 static Reloc::Model getEffectiveRelocModel(const Triple &TT,
179                                            Optional<Reloc::Model> RM) {
180   if (!RM.hasValue())
181     // Default relocation model on Darwin is PIC.
182     return TT.isOSBinFormatMachO() ? Reloc::PIC_ : Reloc::Static;
183 
184   if (*RM == Reloc::ROPI || *RM == Reloc::RWPI || *RM == Reloc::ROPI_RWPI)
185     assert(TT.isOSBinFormatELF() &&
186            "ROPI/RWPI currently only supported for ELF");
187 
188   // DynamicNoPIC is only used on darwin.
189   if (*RM == Reloc::DynamicNoPIC && !TT.isOSDarwin())
190     return Reloc::Static;
191 
192   return *RM;
193 }
194 
195 static CodeModel::Model getEffectiveCodeModel(Optional<CodeModel::Model> CM) {
196   if (CM)
197     return *CM;
198   return CodeModel::Small;
199 }
200 
201 /// Create an ARM architecture model.
202 ///
203 ARMBaseTargetMachine::ARMBaseTargetMachine(const Target &T, const Triple &TT,
204                                            StringRef CPU, StringRef FS,
205                                            const TargetOptions &Options,
206                                            Optional<Reloc::Model> RM,
207                                            Optional<CodeModel::Model> CM,
208                                            CodeGenOpt::Level OL, bool isLittle)
209     : LLVMTargetMachine(T, computeDataLayout(TT, CPU, Options, isLittle), TT,
210                         CPU, FS, Options, getEffectiveRelocModel(TT, RM),
211                         getEffectiveCodeModel(CM), OL),
212       TargetABI(computeTargetABI(TT, CPU, Options)),
213       TLOF(createTLOF(getTargetTriple())), isLittle(isLittle) {
214 
215   // Default to triple-appropriate float ABI
216   if (Options.FloatABIType == FloatABI::Default) {
217     if (TargetTriple.getEnvironment() == Triple::GNUEABIHF ||
218         TargetTriple.getEnvironment() == Triple::MuslEABIHF ||
219         TargetTriple.getEnvironment() == Triple::EABIHF ||
220         TargetTriple.isOSWindows() ||
221         TargetABI == ARMBaseTargetMachine::ARM_ABI_AAPCS16)
222       this->Options.FloatABIType = FloatABI::Hard;
223     else
224       this->Options.FloatABIType = FloatABI::Soft;
225   }
226 
227   // Default to triple-appropriate EABI
228   if (Options.EABIVersion == EABI::Default ||
229       Options.EABIVersion == EABI::Unknown) {
230     // musl is compatible with glibc with regard to EABI version
231     if ((TargetTriple.getEnvironment() == Triple::GNUEABI ||
232          TargetTriple.getEnvironment() == Triple::GNUEABIHF ||
233          TargetTriple.getEnvironment() == Triple::MuslEABI ||
234          TargetTriple.getEnvironment() == Triple::MuslEABIHF) &&
235         !(TargetTriple.isOSWindows() || TargetTriple.isOSDarwin()))
236       this->Options.EABIVersion = EABI::GNU;
237     else
238       this->Options.EABIVersion = EABI::EABI5;
239   }
240 
241   if (TT.isOSBinFormatMachO())
242     this->Options.TrapUnreachable = true;
243 
244   initAsmInfo();
245 }
246 
247 ARMBaseTargetMachine::~ARMBaseTargetMachine() = default;
248 
249 const ARMSubtarget *
250 ARMBaseTargetMachine::getSubtargetImpl(const Function &F) const {
251   Attribute CPUAttr = F.getFnAttribute("target-cpu");
252   Attribute FSAttr = F.getFnAttribute("target-features");
253 
254   std::string CPU = !CPUAttr.hasAttribute(Attribute::None)
255                         ? CPUAttr.getValueAsString().str()
256                         : TargetCPU;
257   std::string FS = !FSAttr.hasAttribute(Attribute::None)
258                        ? FSAttr.getValueAsString().str()
259                        : TargetFS;
260 
261   // FIXME: This is related to the code below to reset the target options,
262   // we need to know whether or not the soft float flag is set on the
263   // function before we can generate a subtarget. We also need to use
264   // it as a key for the subtarget since that can be the only difference
265   // between two functions.
266   bool SoftFloat =
267       F.getFnAttribute("use-soft-float").getValueAsString() == "true";
268   // If the soft float attribute is set on the function turn on the soft float
269   // subtarget feature.
270   if (SoftFloat)
271     FS += FS.empty() ? "+soft-float" : ",+soft-float";
272 
273   auto &I = SubtargetMap[CPU + FS];
274   if (!I) {
275     // This needs to be done before we create a new subtarget since any
276     // creation will depend on the TM and the code generation flags on the
277     // function that reside in TargetOptions.
278     resetTargetOptions(F);
279     I = llvm::make_unique<ARMSubtarget>(TargetTriple, CPU, FS, *this, isLittle);
280 
281     if (!I->isThumb() && !I->hasARMOps())
282       F.getContext().emitError("Function '" + F.getName() + "' uses ARM "
283           "instructions, but the target does not support ARM mode execution.");
284   }
285 
286   return I.get();
287 }
288 
289 TargetTransformInfo
290 ARMBaseTargetMachine::getTargetTransformInfo(const Function &F) {
291   return TargetTransformInfo(ARMTTIImpl(this, F));
292 }
293 
294 ARMLETargetMachine::ARMLETargetMachine(const Target &T, const Triple &TT,
295                                        StringRef CPU, StringRef FS,
296                                        const TargetOptions &Options,
297                                        Optional<Reloc::Model> RM,
298                                        Optional<CodeModel::Model> CM,
299                                        CodeGenOpt::Level OL, bool JIT)
300     : ARMBaseTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL, true) {}
301 
302 ARMBETargetMachine::ARMBETargetMachine(const Target &T, const Triple &TT,
303                                        StringRef CPU, StringRef FS,
304                                        const TargetOptions &Options,
305                                        Optional<Reloc::Model> RM,
306                                        Optional<CodeModel::Model> CM,
307                                        CodeGenOpt::Level OL, bool JIT)
308     : ARMBaseTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL, false) {}
309 
310 namespace {
311 
312 /// ARM Code Generator Pass Configuration Options.
313 class ARMPassConfig : public TargetPassConfig {
314 public:
315   ARMPassConfig(ARMBaseTargetMachine &TM, PassManagerBase &PM)
316       : TargetPassConfig(TM, PM) {
317     if (TM.getOptLevel() != CodeGenOpt::None) {
318       ARMGenSubtargetInfo STI(TM.getTargetTriple(), TM.getTargetCPU(),
319                               TM.getTargetFeatureString());
320       if (STI.hasFeature(ARM::FeatureUseMISched))
321         substitutePass(&PostRASchedulerID, &PostMachineSchedulerID);
322     }
323   }
324 
325   ARMBaseTargetMachine &getARMTargetMachine() const {
326     return getTM<ARMBaseTargetMachine>();
327   }
328 
329   ScheduleDAGInstrs *
330   createMachineScheduler(MachineSchedContext *C) const override {
331     ScheduleDAGMILive *DAG = createGenericSchedLive(C);
332     // add DAG Mutations here.
333     const ARMSubtarget &ST = C->MF->getSubtarget<ARMSubtarget>();
334     if (ST.hasFusion())
335       DAG->addMutation(createARMMacroFusionDAGMutation());
336     return DAG;
337   }
338 
339   ScheduleDAGInstrs *
340   createPostMachineScheduler(MachineSchedContext *C) const override {
341     ScheduleDAGMI *DAG = createGenericSchedPostRA(C);
342     // add DAG Mutations here.
343     const ARMSubtarget &ST = C->MF->getSubtarget<ARMSubtarget>();
344     if (ST.hasFusion())
345       DAG->addMutation(createARMMacroFusionDAGMutation());
346     return DAG;
347   }
348 
349   void addIRPasses() override;
350   bool addPreISel() override;
351   bool addInstSelector() override;
352   bool addIRTranslator() override;
353   bool addLegalizeMachineIR() override;
354   bool addRegBankSelect() override;
355   bool addGlobalInstructionSelect() override;
356   void addPreRegAlloc() override;
357   void addPreSched2() override;
358   void addPreEmitPass() override;
359 };
360 
361 class ARMExecutionDomainFix : public ExecutionDomainFix {
362 public:
363   static char ID;
364   ARMExecutionDomainFix() : ExecutionDomainFix(ID, ARM::DPRRegClass) {}
365   StringRef getPassName() const override {
366     return "ARM Execution Domain Fix";
367   }
368 };
369 char ARMExecutionDomainFix::ID;
370 
371 } // end anonymous namespace
372 
373 INITIALIZE_PASS_BEGIN(ARMExecutionDomainFix, "arm-execution-domain-fix",
374   "ARM Execution Domain Fix", false, false)
375 INITIALIZE_PASS_DEPENDENCY(ReachingDefAnalysis)
376 INITIALIZE_PASS_END(ARMExecutionDomainFix, "arm-execution-domain-fix",
377   "ARM Execution Domain Fix", false, false)
378 
379 TargetPassConfig *ARMBaseTargetMachine::createPassConfig(PassManagerBase &PM) {
380   return new ARMPassConfig(*this, PM);
381 }
382 
383 void ARMPassConfig::addIRPasses() {
384   if (TM->Options.ThreadModel == ThreadModel::Single)
385     addPass(createLowerAtomicPass());
386   else
387     addPass(createAtomicExpandPass());
388 
389   // Cmpxchg instructions are often used with a subsequent comparison to
390   // determine whether it succeeded. We can exploit existing control-flow in
391   // ldrex/strex loops to simplify this, but it needs tidying up.
392   if (TM->getOptLevel() != CodeGenOpt::None && EnableAtomicTidy)
393     addPass(createCFGSimplificationPass(
394         1, false, false, true, true, [this](const Function &F) {
395           const auto &ST = this->TM->getSubtarget<ARMSubtarget>(F);
396           return ST.hasAnyDataBarrier() && !ST.isThumb1Only();
397         }));
398 
399   TargetPassConfig::addIRPasses();
400 
401   // Match interleaved memory accesses to ldN/stN intrinsics.
402   if (TM->getOptLevel() != CodeGenOpt::None)
403     addPass(createInterleavedAccessPass());
404 }
405 
406 bool ARMPassConfig::addPreISel() {
407   if ((TM->getOptLevel() != CodeGenOpt::None &&
408        EnableGlobalMerge == cl::BOU_UNSET) ||
409       EnableGlobalMerge == cl::BOU_TRUE) {
410     // FIXME: This is using the thumb1 only constant value for
411     // maximal global offset for merging globals. We may want
412     // to look into using the old value for non-thumb1 code of
413     // 4095 based on the TargetMachine, but this starts to become
414     // tricky when doing code gen per function.
415     bool OnlyOptimizeForSize = (TM->getOptLevel() < CodeGenOpt::Aggressive) &&
416                                (EnableGlobalMerge == cl::BOU_UNSET);
417     // Merging of extern globals is enabled by default on non-Mach-O as we
418     // expect it to be generally either beneficial or harmless. On Mach-O it
419     // is disabled as we emit the .subsections_via_symbols directive which
420     // means that merging extern globals is not safe.
421     bool MergeExternalByDefault = !TM->getTargetTriple().isOSBinFormatMachO();
422     addPass(createGlobalMergePass(TM, 127, OnlyOptimizeForSize,
423                                   MergeExternalByDefault));
424   }
425 
426   return false;
427 }
428 
429 bool ARMPassConfig::addInstSelector() {
430   addPass(createARMISelDag(getARMTargetMachine(), getOptLevel()));
431   return false;
432 }
433 
434 bool ARMPassConfig::addIRTranslator() {
435   addPass(new IRTranslator());
436   return false;
437 }
438 
439 bool ARMPassConfig::addLegalizeMachineIR() {
440   addPass(new Legalizer());
441   return false;
442 }
443 
444 bool ARMPassConfig::addRegBankSelect() {
445   addPass(new RegBankSelect());
446   return false;
447 }
448 
449 bool ARMPassConfig::addGlobalInstructionSelect() {
450   addPass(new InstructionSelect());
451   return false;
452 }
453 
454 void ARMPassConfig::addPreRegAlloc() {
455   if (getOptLevel() != CodeGenOpt::None) {
456     addPass(createMLxExpansionPass());
457 
458     if (EnableARMLoadStoreOpt)
459       addPass(createARMLoadStoreOptimizationPass(/* pre-register alloc */ true));
460 
461     if (!DisableA15SDOptimization)
462       addPass(createA15SDOptimizerPass());
463   }
464 }
465 
466 void ARMPassConfig::addPreSched2() {
467   if (getOptLevel() != CodeGenOpt::None) {
468     if (EnableARMLoadStoreOpt)
469       addPass(createARMLoadStoreOptimizationPass());
470 
471     addPass(new ARMExecutionDomainFix());
472     addPass(createBreakFalseDeps());
473   }
474 
475   // Expand some pseudo instructions into multiple instructions to allow
476   // proper scheduling.
477   addPass(createARMExpandPseudoPass());
478 
479   if (getOptLevel() != CodeGenOpt::None) {
480     // in v8, IfConversion depends on Thumb instruction widths
481     addPass(createThumb2SizeReductionPass([this](const Function &F) {
482       return this->TM->getSubtarget<ARMSubtarget>(F).restrictIT();
483     }));
484 
485     addPass(createIfConverter([](const MachineFunction &MF) {
486       return !MF.getSubtarget<ARMSubtarget>().isThumb1Only();
487     }));
488   }
489   addPass(createThumb2ITBlockPass());
490 }
491 
492 void ARMPassConfig::addPreEmitPass() {
493   addPass(createThumb2SizeReductionPass());
494 
495   // Constant island pass work on unbundled instructions.
496   addPass(createUnpackMachineBundles([](const MachineFunction &MF) {
497     return MF.getSubtarget<ARMSubtarget>().isThumb2();
498   }));
499 
500   // Don't optimize barriers at -O0.
501   if (getOptLevel() != CodeGenOpt::None)
502     addPass(createARMOptimizeBarriersPass());
503 
504   addPass(createARMConstantIslandPass());
505 }
506