1 //===-- AArch64TargetMachine.cpp - Define TargetMachine for AArch64 -------===//
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 "AArch64TargetMachine.h"
14 #include "AArch64.h"
15 #include "AArch64MacroFusion.h"
16 #include "AArch64Subtarget.h"
17 #include "AArch64TargetObjectFile.h"
18 #include "AArch64TargetTransformInfo.h"
19 #include "MCTargetDesc/AArch64MCTargetDesc.h"
20 #include "llvm/ADT/STLExtras.h"
21 #include "llvm/ADT/Triple.h"
22 #include "llvm/Analysis/TargetTransformInfo.h"
23 #include "llvm/CodeGen/GlobalISel/IRTranslator.h"
24 #include "llvm/CodeGen/GlobalISel/InstructionSelect.h"
25 #include "llvm/CodeGen/GlobalISel/Legalizer.h"
26 #include "llvm/CodeGen/GlobalISel/Localizer.h"
27 #include "llvm/CodeGen/GlobalISel/RegBankSelect.h"
28 #include "llvm/CodeGen/MachineScheduler.h"
29 #include "llvm/CodeGen/Passes.h"
30 #include "llvm/CodeGen/TargetPassConfig.h"
31 #include "llvm/IR/Attributes.h"
32 #include "llvm/IR/Function.h"
33 #include "llvm/MC/MCTargetOptions.h"
34 #include "llvm/Pass.h"
35 #include "llvm/Support/CodeGen.h"
36 #include "llvm/Support/CommandLine.h"
37 #include "llvm/Support/TargetRegistry.h"
38 #include "llvm/Target/TargetLoweringObjectFile.h"
39 #include "llvm/Target/TargetOptions.h"
40 #include "llvm/Transforms/Scalar.h"
41 #include <memory>
42 #include <string>
43 
44 using namespace llvm;
45 
46 static cl::opt<bool> EnableCCMP("aarch64-enable-ccmp",
47                                 cl::desc("Enable the CCMP formation pass"),
48                                 cl::init(true), cl::Hidden);
49 
50 static cl::opt<bool>
51     EnableCondBrTuning("aarch64-enable-cond-br-tune",
52                        cl::desc("Enable the conditional branch tuning pass"),
53                        cl::init(true), cl::Hidden);
54 
55 static cl::opt<bool> EnableMCR("aarch64-enable-mcr",
56                                cl::desc("Enable the machine combiner pass"),
57                                cl::init(true), cl::Hidden);
58 
59 static cl::opt<bool> EnableStPairSuppress("aarch64-enable-stp-suppress",
60                                           cl::desc("Suppress STP for AArch64"),
61                                           cl::init(true), cl::Hidden);
62 
63 static cl::opt<bool> EnableAdvSIMDScalar(
64     "aarch64-enable-simd-scalar",
65     cl::desc("Enable use of AdvSIMD scalar integer instructions"),
66     cl::init(false), cl::Hidden);
67 
68 static cl::opt<bool>
69     EnablePromoteConstant("aarch64-enable-promote-const",
70                           cl::desc("Enable the promote constant pass"),
71                           cl::init(true), cl::Hidden);
72 
73 static cl::opt<bool> EnableCollectLOH(
74     "aarch64-enable-collect-loh",
75     cl::desc("Enable the pass that emits the linker optimization hints (LOH)"),
76     cl::init(true), cl::Hidden);
77 
78 static cl::opt<bool>
79     EnableDeadRegisterElimination("aarch64-enable-dead-defs", cl::Hidden,
80                                   cl::desc("Enable the pass that removes dead"
81                                            " definitons and replaces stores to"
82                                            " them with stores to the zero"
83                                            " register"),
84                                   cl::init(true));
85 
86 static cl::opt<bool> EnableRedundantCopyElimination(
87     "aarch64-enable-copyelim",
88     cl::desc("Enable the redundant copy elimination pass"), cl::init(true),
89     cl::Hidden);
90 
91 static cl::opt<bool> EnableLoadStoreOpt("aarch64-enable-ldst-opt",
92                                         cl::desc("Enable the load/store pair"
93                                                  " optimization pass"),
94                                         cl::init(true), cl::Hidden);
95 
96 static cl::opt<bool> EnableAtomicTidy(
97     "aarch64-enable-atomic-cfg-tidy", cl::Hidden,
98     cl::desc("Run SimplifyCFG after expanding atomic operations"
99              " to make use of cmpxchg flow-based information"),
100     cl::init(true));
101 
102 static cl::opt<bool>
103 EnableEarlyIfConversion("aarch64-enable-early-ifcvt", cl::Hidden,
104                         cl::desc("Run early if-conversion"),
105                         cl::init(true));
106 
107 static cl::opt<bool>
108     EnableCondOpt("aarch64-enable-condopt",
109                   cl::desc("Enable the condition optimizer pass"),
110                   cl::init(true), cl::Hidden);
111 
112 static cl::opt<bool>
113 EnableA53Fix835769("aarch64-fix-cortex-a53-835769", cl::Hidden,
114                 cl::desc("Work around Cortex-A53 erratum 835769"),
115                 cl::init(false));
116 
117 static cl::opt<bool>
118     EnableGEPOpt("aarch64-enable-gep-opt", cl::Hidden,
119                  cl::desc("Enable optimizations on complex GEPs"),
120                  cl::init(false));
121 
122 static cl::opt<bool>
123     BranchRelaxation("aarch64-enable-branch-relax", cl::Hidden, cl::init(true),
124                      cl::desc("Relax out of range conditional branches"));
125 
126 // FIXME: Unify control over GlobalMerge.
127 static cl::opt<cl::boolOrDefault>
128     EnableGlobalMerge("aarch64-enable-global-merge", cl::Hidden,
129                       cl::desc("Enable the global merge pass"));
130 
131 static cl::opt<bool>
132     EnableLoopDataPrefetch("aarch64-enable-loop-data-prefetch", cl::Hidden,
133                            cl::desc("Enable the loop data prefetch pass"),
134                            cl::init(true));
135 
136 static cl::opt<int> EnableGlobalISelAtO(
137     "aarch64-enable-global-isel-at-O", cl::Hidden,
138     cl::desc("Enable GlobalISel at or below an opt level (-1 to disable)"),
139     cl::init(0));
140 
141 static cl::opt<bool> EnableFalkorHWPFFix("aarch64-enable-falkor-hwpf-fix",
142                                          cl::init(true), cl::Hidden);
143 
144 extern "C" void LLVMInitializeAArch64Target() {
145   // Register the target.
146   RegisterTargetMachine<AArch64leTargetMachine> X(getTheAArch64leTarget());
147   RegisterTargetMachine<AArch64beTargetMachine> Y(getTheAArch64beTarget());
148   RegisterTargetMachine<AArch64leTargetMachine> Z(getTheARM64Target());
149   auto PR = PassRegistry::getPassRegistry();
150   initializeGlobalISel(*PR);
151   initializeAArch64A53Fix835769Pass(*PR);
152   initializeAArch64A57FPLoadBalancingPass(*PR);
153   initializeAArch64AdvSIMDScalarPass(*PR);
154   initializeAArch64CollectLOHPass(*PR);
155   initializeAArch64ConditionalComparesPass(*PR);
156   initializeAArch64ConditionOptimizerPass(*PR);
157   initializeAArch64DeadRegisterDefinitionsPass(*PR);
158   initializeAArch64ExpandPseudoPass(*PR);
159   initializeAArch64LoadStoreOptPass(*PR);
160   initializeAArch64SIMDInstrOptPass(*PR);
161   initializeAArch64PromoteConstantPass(*PR);
162   initializeAArch64RedundantCopyEliminationPass(*PR);
163   initializeAArch64StorePairSuppressPass(*PR);
164   initializeFalkorHWPFFixPass(*PR);
165   initializeFalkorMarkStridedAccessesLegacyPass(*PR);
166   initializeLDTLSCleanupPass(*PR);
167 }
168 
169 //===----------------------------------------------------------------------===//
170 // AArch64 Lowering public interface.
171 //===----------------------------------------------------------------------===//
172 static std::unique_ptr<TargetLoweringObjectFile> createTLOF(const Triple &TT) {
173   if (TT.isOSBinFormatMachO())
174     return llvm::make_unique<AArch64_MachoTargetObjectFile>();
175   if (TT.isOSBinFormatCOFF())
176     return llvm::make_unique<AArch64_COFFTargetObjectFile>();
177 
178   return llvm::make_unique<AArch64_ELFTargetObjectFile>();
179 }
180 
181 // Helper function to build a DataLayout string
182 static std::string computeDataLayout(const Triple &TT,
183                                      const MCTargetOptions &Options,
184                                      bool LittleEndian) {
185   if (Options.getABIName() == "ilp32")
186     return "e-m:e-p:32:32-i8:8-i16:16-i64:64-S128";
187   if (TT.isOSBinFormatMachO())
188     return "e-m:o-i64:64-i128:128-n32:64-S128";
189   if (TT.isOSBinFormatCOFF())
190     return "e-m:w-p:64:64-i32:32-i64:64-i128:128-n32:64-S128";
191   if (LittleEndian)
192     return "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128";
193   return "E-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128";
194 }
195 
196 static Reloc::Model getEffectiveRelocModel(const Triple &TT,
197                                            Optional<Reloc::Model> RM) {
198   // AArch64 Darwin is always PIC.
199   if (TT.isOSDarwin())
200     return Reloc::PIC_;
201   // On ELF platforms the default static relocation model has a smart enough
202   // linker to cope with referencing external symbols defined in a shared
203   // library. Hence DynamicNoPIC doesn't need to be promoted to PIC.
204   if (!RM.hasValue() || *RM == Reloc::DynamicNoPIC)
205     return Reloc::Static;
206   return *RM;
207 }
208 
209 static CodeModel::Model getEffectiveCodeModel(const Triple &TT,
210                                               Optional<CodeModel::Model> CM,
211                                               bool JIT) {
212   if (CM) {
213     if (*CM != CodeModel::Small && *CM != CodeModel::Tiny &&
214         *CM != CodeModel::Large) {
215       if (!TT.isOSFuchsia())
216         report_fatal_error(
217             "Only small, tiny and large code models are allowed on AArch64");
218       else if (*CM != CodeModel::Kernel)
219         report_fatal_error("Only small, tiny, kernel, and large code models "
220                            "are allowed on AArch64");
221     } else if (*CM == CodeModel::Tiny && !TT.isOSBinFormatELF())
222       report_fatal_error("tiny code model is only supported on ELF");
223     return *CM;
224   }
225   // The default MCJIT memory managers make no guarantees about where they can
226   // find an executable page; JITed code needs to be able to refer to globals
227   // no matter how far away they are.
228   if (JIT)
229     return CodeModel::Large;
230   return CodeModel::Small;
231 }
232 
233 /// Create an AArch64 architecture model.
234 ///
235 AArch64TargetMachine::AArch64TargetMachine(const Target &T, const Triple &TT,
236                                            StringRef CPU, StringRef FS,
237                                            const TargetOptions &Options,
238                                            Optional<Reloc::Model> RM,
239                                            Optional<CodeModel::Model> CM,
240                                            CodeGenOpt::Level OL, bool JIT,
241                                            bool LittleEndian)
242     : LLVMTargetMachine(T,
243                         computeDataLayout(TT, Options.MCOptions, LittleEndian),
244                         TT, CPU, FS, Options, getEffectiveRelocModel(TT, RM),
245                         getEffectiveCodeModel(TT, CM, JIT), OL),
246       TLOF(createTLOF(getTargetTriple())), isLittle(LittleEndian) {
247   initAsmInfo();
248 
249   if (TT.isOSBinFormatMachO()) {
250     this->Options.TrapUnreachable = true;
251     this->Options.NoTrapAfterNoreturn = true;
252   }
253 
254   // Enable GlobalISel at or below EnableGlobalISelAt0.
255   if (getOptLevel() <= EnableGlobalISelAtO)
256     setGlobalISel(true);
257 
258   // AArch64 supports the MachineOutliner.
259   setMachineOutliner(true);
260 
261   // AArch64 supports default outlining behaviour.
262   setSupportsDefaultOutlining(true);
263 }
264 
265 AArch64TargetMachine::~AArch64TargetMachine() = default;
266 
267 const AArch64Subtarget *
268 AArch64TargetMachine::getSubtargetImpl(const Function &F) const {
269   Attribute CPUAttr = F.getFnAttribute("target-cpu");
270   Attribute FSAttr = F.getFnAttribute("target-features");
271 
272   std::string CPU = !CPUAttr.hasAttribute(Attribute::None)
273                         ? CPUAttr.getValueAsString().str()
274                         : TargetCPU;
275   std::string FS = !FSAttr.hasAttribute(Attribute::None)
276                        ? FSAttr.getValueAsString().str()
277                        : TargetFS;
278 
279   auto &I = SubtargetMap[CPU + FS];
280   if (!I) {
281     // This needs to be done before we create a new subtarget since any
282     // creation will depend on the TM and the code generation flags on the
283     // function that reside in TargetOptions.
284     resetTargetOptions(F);
285     I = llvm::make_unique<AArch64Subtarget>(TargetTriple, CPU, FS, *this,
286                                             isLittle);
287   }
288   return I.get();
289 }
290 
291 void AArch64leTargetMachine::anchor() { }
292 
293 AArch64leTargetMachine::AArch64leTargetMachine(
294     const Target &T, const Triple &TT, StringRef CPU, StringRef FS,
295     const TargetOptions &Options, Optional<Reloc::Model> RM,
296     Optional<CodeModel::Model> CM, CodeGenOpt::Level OL, bool JIT)
297     : AArch64TargetMachine(T, TT, CPU, FS, Options, RM, CM, OL, JIT, true) {}
298 
299 void AArch64beTargetMachine::anchor() { }
300 
301 AArch64beTargetMachine::AArch64beTargetMachine(
302     const Target &T, const Triple &TT, StringRef CPU, StringRef FS,
303     const TargetOptions &Options, Optional<Reloc::Model> RM,
304     Optional<CodeModel::Model> CM, CodeGenOpt::Level OL, bool JIT)
305     : AArch64TargetMachine(T, TT, CPU, FS, Options, RM, CM, OL, JIT, false) {}
306 
307 namespace {
308 
309 /// AArch64 Code Generator Pass Configuration Options.
310 class AArch64PassConfig : public TargetPassConfig {
311 public:
312   AArch64PassConfig(AArch64TargetMachine &TM, PassManagerBase &PM)
313       : TargetPassConfig(TM, PM) {
314     if (TM.getOptLevel() != CodeGenOpt::None)
315       substitutePass(&PostRASchedulerID, &PostMachineSchedulerID);
316   }
317 
318   AArch64TargetMachine &getAArch64TargetMachine() const {
319     return getTM<AArch64TargetMachine>();
320   }
321 
322   ScheduleDAGInstrs *
323   createMachineScheduler(MachineSchedContext *C) const override {
324     const AArch64Subtarget &ST = C->MF->getSubtarget<AArch64Subtarget>();
325     ScheduleDAGMILive *DAG = createGenericSchedLive(C);
326     DAG->addMutation(createLoadClusterDAGMutation(DAG->TII, DAG->TRI));
327     DAG->addMutation(createStoreClusterDAGMutation(DAG->TII, DAG->TRI));
328     if (ST.hasFusion())
329       DAG->addMutation(createAArch64MacroFusionDAGMutation());
330     return DAG;
331   }
332 
333   ScheduleDAGInstrs *
334   createPostMachineScheduler(MachineSchedContext *C) const override {
335     const AArch64Subtarget &ST = C->MF->getSubtarget<AArch64Subtarget>();
336     if (ST.hasFusion()) {
337       // Run the Macro Fusion after RA again since literals are expanded from
338       // pseudos then (v. addPreSched2()).
339       ScheduleDAGMI *DAG = createGenericSchedPostRA(C);
340       DAG->addMutation(createAArch64MacroFusionDAGMutation());
341       return DAG;
342     }
343 
344     return nullptr;
345   }
346 
347   void addIRPasses()  override;
348   bool addPreISel() override;
349   bool addInstSelector() override;
350   bool addIRTranslator() override;
351   bool addLegalizeMachineIR() override;
352   bool addRegBankSelect() override;
353   void addPreGlobalInstructionSelect() override;
354   bool addGlobalInstructionSelect() override;
355   bool addILPOpts() override;
356   void addPreRegAlloc() override;
357   void addPostRegAlloc() override;
358   void addPreSched2() override;
359   void addPreEmitPass() override;
360 };
361 
362 } // end anonymous namespace
363 
364 TargetTransformInfo
365 AArch64TargetMachine::getTargetTransformInfo(const Function &F) {
366   return TargetTransformInfo(AArch64TTIImpl(this, F));
367 }
368 
369 TargetPassConfig *AArch64TargetMachine::createPassConfig(PassManagerBase &PM) {
370   return new AArch64PassConfig(*this, PM);
371 }
372 
373 void AArch64PassConfig::addIRPasses() {
374   // Always expand atomic operations, we don't deal with atomicrmw or cmpxchg
375   // ourselves.
376   addPass(createAtomicExpandPass());
377 
378   // Cmpxchg instructions are often used with a subsequent comparison to
379   // determine whether it succeeded. We can exploit existing control-flow in
380   // ldrex/strex loops to simplify this, but it needs tidying up.
381   if (TM->getOptLevel() != CodeGenOpt::None && EnableAtomicTidy)
382     addPass(createCFGSimplificationPass(1, true, true, false, true));
383 
384   // Run LoopDataPrefetch
385   //
386   // Run this before LSR to remove the multiplies involved in computing the
387   // pointer values N iterations ahead.
388   if (TM->getOptLevel() != CodeGenOpt::None) {
389     if (EnableLoopDataPrefetch)
390       addPass(createLoopDataPrefetchPass());
391     if (EnableFalkorHWPFFix)
392       addPass(createFalkorMarkStridedAccessesPass());
393   }
394 
395   TargetPassConfig::addIRPasses();
396 
397   // Match interleaved memory accesses to ldN/stN intrinsics.
398   if (TM->getOptLevel() != CodeGenOpt::None)
399     addPass(createInterleavedAccessPass());
400 
401   if (TM->getOptLevel() == CodeGenOpt::Aggressive && EnableGEPOpt) {
402     // Call SeparateConstOffsetFromGEP pass to extract constants within indices
403     // and lower a GEP with multiple indices to either arithmetic operations or
404     // multiple GEPs with single index.
405     addPass(createSeparateConstOffsetFromGEPPass(true));
406     // Call EarlyCSE pass to find and remove subexpressions in the lowered
407     // result.
408     addPass(createEarlyCSEPass());
409     // Do loop invariant code motion in case part of the lowered result is
410     // invariant.
411     addPass(createLICMPass());
412   }
413 }
414 
415 // Pass Pipeline Configuration
416 bool AArch64PassConfig::addPreISel() {
417   // Run promote constant before global merge, so that the promoted constants
418   // get a chance to be merged
419   if (TM->getOptLevel() != CodeGenOpt::None && EnablePromoteConstant)
420     addPass(createAArch64PromoteConstantPass());
421   // FIXME: On AArch64, this depends on the type.
422   // Basically, the addressable offsets are up to 4095 * Ty.getSizeInBytes().
423   // and the offset has to be a multiple of the related size in bytes.
424   if ((TM->getOptLevel() != CodeGenOpt::None &&
425        EnableGlobalMerge == cl::BOU_UNSET) ||
426       EnableGlobalMerge == cl::BOU_TRUE) {
427     bool OnlyOptimizeForSize = (TM->getOptLevel() < CodeGenOpt::Aggressive) &&
428                                (EnableGlobalMerge == cl::BOU_UNSET);
429     addPass(createGlobalMergePass(TM, 4095, OnlyOptimizeForSize));
430   }
431 
432   return false;
433 }
434 
435 bool AArch64PassConfig::addInstSelector() {
436   addPass(createAArch64ISelDag(getAArch64TargetMachine(), getOptLevel()));
437 
438   // For ELF, cleanup any local-dynamic TLS accesses (i.e. combine as many
439   // references to _TLS_MODULE_BASE_ as possible.
440   if (TM->getTargetTriple().isOSBinFormatELF() &&
441       getOptLevel() != CodeGenOpt::None)
442     addPass(createAArch64CleanupLocalDynamicTLSPass());
443 
444   return false;
445 }
446 
447 bool AArch64PassConfig::addIRTranslator() {
448   addPass(new IRTranslator());
449   return false;
450 }
451 
452 bool AArch64PassConfig::addLegalizeMachineIR() {
453   addPass(new Legalizer());
454   return false;
455 }
456 
457 bool AArch64PassConfig::addRegBankSelect() {
458   addPass(new RegBankSelect());
459   return false;
460 }
461 
462 void AArch64PassConfig::addPreGlobalInstructionSelect() {
463   // Workaround the deficiency of the fast register allocator.
464   if (TM->getOptLevel() == CodeGenOpt::None)
465     addPass(new Localizer());
466 }
467 
468 bool AArch64PassConfig::addGlobalInstructionSelect() {
469   addPass(new InstructionSelect());
470   return false;
471 }
472 
473 bool AArch64PassConfig::addILPOpts() {
474   if (EnableCondOpt)
475     addPass(createAArch64ConditionOptimizerPass());
476   if (EnableCCMP)
477     addPass(createAArch64ConditionalCompares());
478   if (EnableMCR)
479     addPass(&MachineCombinerID);
480   if (EnableCondBrTuning)
481     addPass(createAArch64CondBrTuning());
482   if (EnableEarlyIfConversion)
483     addPass(&EarlyIfConverterID);
484   if (EnableStPairSuppress)
485     addPass(createAArch64StorePairSuppressPass());
486   addPass(createAArch64SIMDInstrOptPass());
487   return true;
488 }
489 
490 void AArch64PassConfig::addPreRegAlloc() {
491   // Change dead register definitions to refer to the zero register.
492   if (TM->getOptLevel() != CodeGenOpt::None && EnableDeadRegisterElimination)
493     addPass(createAArch64DeadRegisterDefinitions());
494 
495   // Use AdvSIMD scalar instructions whenever profitable.
496   if (TM->getOptLevel() != CodeGenOpt::None && EnableAdvSIMDScalar) {
497     addPass(createAArch64AdvSIMDScalar());
498     // The AdvSIMD pass may produce copies that can be rewritten to
499     // be register coaleascer friendly.
500     addPass(&PeepholeOptimizerID);
501   }
502 }
503 
504 void AArch64PassConfig::addPostRegAlloc() {
505   // Remove redundant copy instructions.
506   if (TM->getOptLevel() != CodeGenOpt::None && EnableRedundantCopyElimination)
507     addPass(createAArch64RedundantCopyEliminationPass());
508 
509   if (TM->getOptLevel() != CodeGenOpt::None && usingDefaultRegAlloc())
510     // Improve performance for some FP/SIMD code for A57.
511     addPass(createAArch64A57FPLoadBalancing());
512 }
513 
514 void AArch64PassConfig::addPreSched2() {
515   // Expand some pseudo instructions to allow proper scheduling.
516   addPass(createAArch64ExpandPseudoPass());
517   // Use load/store pair instructions when possible.
518   if (TM->getOptLevel() != CodeGenOpt::None) {
519     if (EnableLoadStoreOpt)
520       addPass(createAArch64LoadStoreOptimizationPass());
521     if (EnableFalkorHWPFFix)
522       addPass(createFalkorHWPFFixPass());
523   }
524 }
525 
526 void AArch64PassConfig::addPreEmitPass() {
527   if (EnableA53Fix835769)
528     addPass(createAArch64A53Fix835769());
529   // Relax conditional branch instructions if they're otherwise out of
530   // range of their destination.
531   if (BranchRelaxation)
532     addPass(&BranchRelaxationPassID);
533 
534   if (TM->getOptLevel() != CodeGenOpt::None && EnableCollectLOH &&
535       TM->getTargetTriple().isOSBinFormatMachO())
536     addPass(createAArch64CollectLOHPass());
537 }
538