1 //===-- ARMTargetMachine.cpp - Define TargetMachine for ARM ---------------===//
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 //
10 //===----------------------------------------------------------------------===//
11 
12 #include "ARMTargetMachine.h"
13 #include "ARM.h"
14 #include "ARMMacroFusion.h"
15 #include "ARMSubtarget.h"
16 #include "ARMTargetObjectFile.h"
17 #include "ARMTargetTransformInfo.h"
18 #include "MCTargetDesc/ARMMCTargetDesc.h"
19 #include "llvm/ADT/Optional.h"
20 #include "llvm/ADT/STLExtras.h"
21 #include "llvm/ADT/StringRef.h"
22 #include "llvm/ADT/Triple.h"
23 #include "llvm/Analysis/TargetTransformInfo.h"
24 #include "llvm/CodeGen/ExecutionDomainFix.h"
25 #include "llvm/CodeGen/GlobalISel/CallLowering.h"
26 #include "llvm/CodeGen/GlobalISel/IRTranslator.h"
27 #include "llvm/CodeGen/GlobalISel/InstructionSelect.h"
28 #include "llvm/CodeGen/GlobalISel/InstructionSelector.h"
29 #include "llvm/CodeGen/GlobalISel/Legalizer.h"
30 #include "llvm/CodeGen/GlobalISel/LegalizerInfo.h"
31 #include "llvm/CodeGen/GlobalISel/RegBankSelect.h"
32 #include "llvm/CodeGen/GlobalISel/RegisterBankInfo.h"
33 #include "llvm/CodeGen/MachineFunction.h"
34 #include "llvm/CodeGen/MachineScheduler.h"
35 #include "llvm/CodeGen/Passes.h"
36 #include "llvm/CodeGen/TargetPassConfig.h"
37 #include "llvm/IR/Attributes.h"
38 #include "llvm/IR/DataLayout.h"
39 #include "llvm/IR/Function.h"
40 #include "llvm/Pass.h"
41 #include "llvm/Support/CodeGen.h"
42 #include "llvm/Support/CommandLine.h"
43 #include "llvm/Support/ErrorHandling.h"
44 #include "llvm/Support/TargetParser.h"
45 #include "llvm/Support/TargetRegistry.h"
46 #include "llvm/Target/TargetLoweringObjectFile.h"
47 #include "llvm/Target/TargetOptions.h"
48 #include "llvm/Transforms/Scalar.h"
49 #include <cassert>
50 #include <memory>
51 #include <string>
52 
53 using namespace llvm;
54 
55 static cl::opt<bool>
56 DisableA15SDOptimization("disable-a15-sd-optimization", cl::Hidden,
57                    cl::desc("Inhibit optimization of S->D register accesses on A15"),
58                    cl::init(false));
59 
60 static cl::opt<bool>
61 EnableAtomicTidy("arm-atomic-cfg-tidy", cl::Hidden,
62                  cl::desc("Run SimplifyCFG after expanding atomic operations"
63                           " to make use of cmpxchg flow-based information"),
64                  cl::init(true));
65 
66 static cl::opt<bool>
67 EnableARMLoadStoreOpt("arm-load-store-opt", cl::Hidden,
68                       cl::desc("Enable ARM load/store optimization pass"),
69                       cl::init(true));
70 
71 // FIXME: Unify control over GlobalMerge.
72 static cl::opt<cl::boolOrDefault>
73 EnableGlobalMerge("arm-global-merge", cl::Hidden,
74                   cl::desc("Enable the global merge pass"));
75 
76 namespace llvm {
77   void initializeARMExecutionDomainFixPass(PassRegistry&);
78 }
79 
80 extern "C" void LLVMInitializeARMTarget() {
81   // Register the target.
82   RegisterTargetMachine<ARMLETargetMachine> X(getTheARMLETarget());
83   RegisterTargetMachine<ARMLETargetMachine> A(getTheThumbLETarget());
84   RegisterTargetMachine<ARMBETargetMachine> Y(getTheARMBETarget());
85   RegisterTargetMachine<ARMBETargetMachine> B(getTheThumbBETarget());
86 
87   PassRegistry &Registry = *PassRegistry::getPassRegistry();
88   initializeGlobalISel(Registry);
89   initializeARMLoadStoreOptPass(Registry);
90   initializeARMPreAllocLoadStoreOptPass(Registry);
91   initializeARMParallelDSPPass(Registry);
92   initializeARMCodeGenPreparePass(Registry);
93   initializeARMConstantIslandsPass(Registry);
94   initializeARMExecutionDomainFixPass(Registry);
95   initializeARMExpandPseudoPass(Registry);
96   initializeThumb2SizeReducePass(Registry);
97 }
98 
99 static std::unique_ptr<TargetLoweringObjectFile> createTLOF(const Triple &TT) {
100   if (TT.isOSBinFormatMachO())
101     return llvm::make_unique<TargetLoweringObjectFileMachO>();
102   if (TT.isOSWindows())
103     return llvm::make_unique<TargetLoweringObjectFileCOFF>();
104   return llvm::make_unique<ARMElfTargetObjectFile>();
105 }
106 
107 static ARMBaseTargetMachine::ARMABI
108 computeTargetABI(const Triple &TT, StringRef CPU,
109                  const TargetOptions &Options) {
110   StringRef ABIName = Options.MCOptions.getABIName();
111 
112   if (ABIName.empty())
113     ABIName = ARM::computeDefaultTargetABI(TT, CPU);
114 
115   if (ABIName == "aapcs16")
116     return ARMBaseTargetMachine::ARM_ABI_AAPCS16;
117   else if (ABIName.startswith("aapcs"))
118     return ARMBaseTargetMachine::ARM_ABI_AAPCS;
119   else if (ABIName.startswith("apcs"))
120     return ARMBaseTargetMachine::ARM_ABI_APCS;
121 
122   llvm_unreachable("Unhandled/unknown ABI Name!");
123   return ARMBaseTargetMachine::ARM_ABI_UNKNOWN;
124 }
125 
126 static std::string computeDataLayout(const Triple &TT, StringRef CPU,
127                                      const TargetOptions &Options,
128                                      bool isLittle) {
129   auto ABI = computeTargetABI(TT, CPU, Options);
130   std::string Ret;
131 
132   if (isLittle)
133     // Little endian.
134     Ret += "e";
135   else
136     // Big endian.
137     Ret += "E";
138 
139   Ret += DataLayout::getManglingComponent(TT);
140 
141   // Pointers are 32 bits and aligned to 32 bits.
142   Ret += "-p:32:32";
143 
144   // ABIs other than APCS have 64 bit integers with natural alignment.
145   if (ABI != ARMBaseTargetMachine::ARM_ABI_APCS)
146     Ret += "-i64:64";
147 
148   // We have 64 bits floats. The APCS ABI requires them to be aligned to 32
149   // bits, others to 64 bits. We always try to align to 64 bits.
150   if (ABI == ARMBaseTargetMachine::ARM_ABI_APCS)
151     Ret += "-f64:32:64";
152 
153   // We have 128 and 64 bit vectors. The APCS ABI aligns them to 32 bits, others
154   // to 64. We always ty to give them natural alignment.
155   if (ABI == ARMBaseTargetMachine::ARM_ABI_APCS)
156     Ret += "-v64:32:64-v128:32:128";
157   else if (ABI != ARMBaseTargetMachine::ARM_ABI_AAPCS16)
158     Ret += "-v128:64:128";
159 
160   // Try to align aggregates to 32 bits (the default is 64 bits, which has no
161   // particular hardware support on 32-bit ARM).
162   Ret += "-a:0:32";
163 
164   // Integer registers are 32 bits.
165   Ret += "-n32";
166 
167   // The stack is 128 bit aligned on NaCl, 64 bit aligned on AAPCS and 32 bit
168   // aligned everywhere else.
169   if (TT.isOSNaCl() || ABI == ARMBaseTargetMachine::ARM_ABI_AAPCS16)
170     Ret += "-S128";
171   else if (ABI == ARMBaseTargetMachine::ARM_ABI_AAPCS)
172     Ret += "-S64";
173   else
174     Ret += "-S32";
175 
176   return Ret;
177 }
178 
179 static Reloc::Model getEffectiveRelocModel(const Triple &TT,
180                                            Optional<Reloc::Model> RM) {
181   if (!RM.hasValue())
182     // Default relocation model on Darwin is PIC.
183     return TT.isOSBinFormatMachO() ? Reloc::PIC_ : Reloc::Static;
184 
185   if (*RM == Reloc::ROPI || *RM == Reloc::RWPI || *RM == Reloc::ROPI_RWPI)
186     assert(TT.isOSBinFormatELF() &&
187            "ROPI/RWPI currently only supported for ELF");
188 
189   // DynamicNoPIC is only used on darwin.
190   if (*RM == Reloc::DynamicNoPIC && !TT.isOSDarwin())
191     return Reloc::Static;
192 
193   return *RM;
194 }
195 
196 /// Create an ARM architecture model.
197 ///
198 ARMBaseTargetMachine::ARMBaseTargetMachine(const Target &T, const Triple &TT,
199                                            StringRef CPU, StringRef FS,
200                                            const TargetOptions &Options,
201                                            Optional<Reloc::Model> RM,
202                                            Optional<CodeModel::Model> CM,
203                                            CodeGenOpt::Level OL, bool isLittle)
204     : LLVMTargetMachine(T, computeDataLayout(TT, CPU, Options, isLittle), TT,
205                         CPU, FS, Options, getEffectiveRelocModel(TT, RM),
206                         getEffectiveCodeModel(CM, CodeModel::Small), OL),
207       TargetABI(computeTargetABI(TT, CPU, Options)),
208       TLOF(createTLOF(getTargetTriple())), isLittle(isLittle) {
209 
210   // Default to triple-appropriate float ABI
211   if (Options.FloatABIType == FloatABI::Default) {
212     if (isTargetHardFloat())
213       this->Options.FloatABIType = FloatABI::Hard;
214     else
215       this->Options.FloatABIType = FloatABI::Soft;
216   }
217 
218   // Default to triple-appropriate EABI
219   if (Options.EABIVersion == EABI::Default ||
220       Options.EABIVersion == EABI::Unknown) {
221     // musl is compatible with glibc with regard to EABI version
222     if ((TargetTriple.getEnvironment() == Triple::GNUEABI ||
223          TargetTriple.getEnvironment() == Triple::GNUEABIHF ||
224          TargetTriple.getEnvironment() == Triple::MuslEABI ||
225          TargetTriple.getEnvironment() == Triple::MuslEABIHF) &&
226         !(TargetTriple.isOSWindows() || TargetTriple.isOSDarwin()))
227       this->Options.EABIVersion = EABI::GNU;
228     else
229       this->Options.EABIVersion = EABI::EABI5;
230   }
231 
232   if (TT.isOSBinFormatMachO()) {
233     this->Options.TrapUnreachable = true;
234     this->Options.NoTrapAfterNoreturn = true;
235   }
236 
237   initAsmInfo();
238 }
239 
240 ARMBaseTargetMachine::~ARMBaseTargetMachine() = default;
241 
242 const ARMSubtarget *
243 ARMBaseTargetMachine::getSubtargetImpl(const Function &F) const {
244   Attribute CPUAttr = F.getFnAttribute("target-cpu");
245   Attribute FSAttr = F.getFnAttribute("target-features");
246 
247   std::string CPU = !CPUAttr.hasAttribute(Attribute::None)
248                         ? CPUAttr.getValueAsString().str()
249                         : TargetCPU;
250   std::string FS = !FSAttr.hasAttribute(Attribute::None)
251                        ? FSAttr.getValueAsString().str()
252                        : TargetFS;
253 
254   // FIXME: This is related to the code below to reset the target options,
255   // we need to know whether or not the soft float flag is set on the
256   // function before we can generate a subtarget. We also need to use
257   // it as a key for the subtarget since that can be the only difference
258   // between two functions.
259   bool SoftFloat =
260       F.getFnAttribute("use-soft-float").getValueAsString() == "true";
261   // If the soft float attribute is set on the function turn on the soft float
262   // subtarget feature.
263   if (SoftFloat)
264     FS += FS.empty() ? "+soft-float" : ",+soft-float";
265 
266   // Use the optminsize to identify the subtarget, but don't use it in the
267   // feature string.
268   std::string Key = CPU + FS;
269   if (F.optForMinSize())
270     Key += "+minsize";
271 
272   auto &I = SubtargetMap[Key];
273   if (!I) {
274     // This needs to be done before we create a new subtarget since any
275     // creation will depend on the TM and the code generation flags on the
276     // function that reside in TargetOptions.
277     resetTargetOptions(F);
278     I = llvm::make_unique<ARMSubtarget>(TargetTriple, CPU, FS, *this, isLittle,
279                                         F.optForMinSize());
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   void addCodeGenPrepare() override;
351   bool addPreISel() override;
352   bool addInstSelector() override;
353   bool addIRTranslator() override;
354   bool addLegalizeMachineIR() override;
355   bool addRegBankSelect() override;
356   bool addGlobalInstructionSelect() override;
357   void addPreRegAlloc() override;
358   void addPreSched2() override;
359   void addPreEmitPass() override;
360 };
361 
362 class ARMExecutionDomainFix : public ExecutionDomainFix {
363 public:
364   static char ID;
365   ARMExecutionDomainFix() : ExecutionDomainFix(ID, ARM::DPRRegClass) {}
366   StringRef getPassName() const override {
367     return "ARM Execution Domain Fix";
368   }
369 };
370 char ARMExecutionDomainFix::ID;
371 
372 } // end anonymous namespace
373 
374 INITIALIZE_PASS_BEGIN(ARMExecutionDomainFix, "arm-execution-domain-fix",
375   "ARM Execution Domain Fix", false, false)
376 INITIALIZE_PASS_DEPENDENCY(ReachingDefAnalysis)
377 INITIALIZE_PASS_END(ARMExecutionDomainFix, "arm-execution-domain-fix",
378   "ARM Execution Domain Fix", false, false)
379 
380 TargetPassConfig *ARMBaseTargetMachine::createPassConfig(PassManagerBase &PM) {
381   return new ARMPassConfig(*this, PM);
382 }
383 
384 void ARMPassConfig::addIRPasses() {
385   if (TM->Options.ThreadModel == ThreadModel::Single)
386     addPass(createLowerAtomicPass());
387   else
388     addPass(createAtomicExpandPass());
389 
390   // Cmpxchg instructions are often used with a subsequent comparison to
391   // determine whether it succeeded. We can exploit existing control-flow in
392   // ldrex/strex loops to simplify this, but it needs tidying up.
393   if (TM->getOptLevel() != CodeGenOpt::None && EnableAtomicTidy)
394     addPass(createCFGSimplificationPass(
395         1, false, false, true, true, [this](const Function &F) {
396           const auto &ST = this->TM->getSubtarget<ARMSubtarget>(F);
397           return ST.hasAnyDataBarrier() && !ST.isThumb1Only();
398         }));
399 
400   TargetPassConfig::addIRPasses();
401 
402   // Match interleaved memory accesses to ldN/stN intrinsics.
403   if (TM->getOptLevel() != CodeGenOpt::None)
404     addPass(createInterleavedAccessPass());
405 }
406 
407 void ARMPassConfig::addCodeGenPrepare() {
408   if (getOptLevel() != CodeGenOpt::None)
409     addPass(createARMCodeGenPreparePass());
410   TargetPassConfig::addCodeGenPrepare();
411 }
412 
413 bool ARMPassConfig::addPreISel() {
414   if (getOptLevel() != CodeGenOpt::None)
415     addPass(createARMParallelDSPPass());
416 
417   if ((TM->getOptLevel() != CodeGenOpt::None &&
418        EnableGlobalMerge == cl::BOU_UNSET) ||
419       EnableGlobalMerge == cl::BOU_TRUE) {
420     // FIXME: This is using the thumb1 only constant value for
421     // maximal global offset for merging globals. We may want
422     // to look into using the old value for non-thumb1 code of
423     // 4095 based on the TargetMachine, but this starts to become
424     // tricky when doing code gen per function.
425     bool OnlyOptimizeForSize = (TM->getOptLevel() < CodeGenOpt::Aggressive) &&
426                                (EnableGlobalMerge == cl::BOU_UNSET);
427     // Merging of extern globals is enabled by default on non-Mach-O as we
428     // expect it to be generally either beneficial or harmless. On Mach-O it
429     // is disabled as we emit the .subsections_via_symbols directive which
430     // means that merging extern globals is not safe.
431     bool MergeExternalByDefault = !TM->getTargetTriple().isOSBinFormatMachO();
432     addPass(createGlobalMergePass(TM, 127, OnlyOptimizeForSize,
433                                   MergeExternalByDefault));
434   }
435 
436   return false;
437 }
438 
439 bool ARMPassConfig::addInstSelector() {
440   addPass(createARMISelDag(getARMTargetMachine(), getOptLevel()));
441   return false;
442 }
443 
444 bool ARMPassConfig::addIRTranslator() {
445   addPass(new IRTranslator());
446   return false;
447 }
448 
449 bool ARMPassConfig::addLegalizeMachineIR() {
450   addPass(new Legalizer());
451   return false;
452 }
453 
454 bool ARMPassConfig::addRegBankSelect() {
455   addPass(new RegBankSelect());
456   return false;
457 }
458 
459 bool ARMPassConfig::addGlobalInstructionSelect() {
460   addPass(new InstructionSelect());
461   return false;
462 }
463 
464 void ARMPassConfig::addPreRegAlloc() {
465   if (getOptLevel() != CodeGenOpt::None) {
466     addPass(createMLxExpansionPass());
467 
468     if (EnableARMLoadStoreOpt)
469       addPass(createARMLoadStoreOptimizationPass(/* pre-register alloc */ true));
470 
471     if (!DisableA15SDOptimization)
472       addPass(createA15SDOptimizerPass());
473   }
474 }
475 
476 void ARMPassConfig::addPreSched2() {
477   if (getOptLevel() != CodeGenOpt::None) {
478     if (EnableARMLoadStoreOpt)
479       addPass(createARMLoadStoreOptimizationPass());
480 
481     addPass(new ARMExecutionDomainFix());
482     addPass(createBreakFalseDeps());
483   }
484 
485   // Expand some pseudo instructions into multiple instructions to allow
486   // proper scheduling.
487   addPass(createARMExpandPseudoPass());
488 
489   if (getOptLevel() != CodeGenOpt::None) {
490     // in v8, IfConversion depends on Thumb instruction widths
491     addPass(createThumb2SizeReductionPass([this](const Function &F) {
492       return this->TM->getSubtarget<ARMSubtarget>(F).restrictIT();
493     }));
494 
495     addPass(createIfConverter([](const MachineFunction &MF) {
496       return !MF.getSubtarget<ARMSubtarget>().isThumb1Only();
497     }));
498   }
499   addPass(createThumb2ITBlockPass());
500 }
501 
502 void ARMPassConfig::addPreEmitPass() {
503   addPass(createThumb2SizeReductionPass());
504 
505   // Constant island pass work on unbundled instructions.
506   addPass(createUnpackMachineBundles([](const MachineFunction &MF) {
507     return MF.getSubtarget<ARMSubtarget>().isThumb2();
508   }));
509 
510   // Don't optimize barriers at -O0.
511   if (getOptLevel() != CodeGenOpt::None)
512     addPass(createARMOptimizeBarriersPass());
513 
514   addPass(createARMConstantIslandPass());
515 }
516