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      1 //===-- AArch64Subtarget.cpp - AArch64 Subtarget Information ----*- C++ -*-===//
      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 // This file implements the AArch64 specific subclass of TargetSubtarget.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "AArch64InstrInfo.h"
     15 #include "AArch64Subtarget.h"
     16 #include "llvm/ADT/SmallVector.h"
     17 #include "llvm/CodeGen/MachineScheduler.h"
     18 #include "llvm/IR/GlobalValue.h"
     19 #include "llvm/Support/TargetRegistry.h"
     20 
     21 using namespace llvm;
     22 
     23 #define DEBUG_TYPE "aarch64-subtarget"
     24 
     25 #define GET_SUBTARGETINFO_CTOR
     26 #define GET_SUBTARGETINFO_TARGET_DESC
     27 #include "AArch64GenSubtargetInfo.inc"
     28 
     29 static cl::opt<bool>
     30 EnableEarlyIfConvert("aarch64-early-ifcvt", cl::desc("Enable the early if "
     31                      "converter pass"), cl::init(true), cl::Hidden);
     32 
     33 AArch64Subtarget &
     34 AArch64Subtarget::initializeSubtargetDependencies(StringRef FS) {
     35   // Determine default and user-specified characteristics
     36 
     37   if (CPUString.empty())
     38     CPUString = "generic";
     39 
     40   ParseSubtargetFeatures(CPUString, FS);
     41   return *this;
     42 }
     43 
     44 AArch64Subtarget::AArch64Subtarget(const std::string &TT,
     45                                    const std::string &CPU,
     46                                    const std::string &FS, TargetMachine &TM,
     47                                    bool LittleEndian)
     48     : AArch64GenSubtargetInfo(TT, CPU, FS), ARMProcFamily(Others),
     49       HasFPARMv8(false), HasNEON(false), HasCrypto(false), HasCRC(false),
     50       HasZeroCycleRegMove(false), HasZeroCycleZeroing(false), CPUString(CPU),
     51       TargetTriple(TT),
     52       // This nested ternary is horrible, but DL needs to be properly
     53       // initialized
     54       // before TLInfo is constructed.
     55       DL(isTargetMachO()
     56              ? "e-m:o-i64:64-i128:128-n32:64-S128"
     57              : (LittleEndian ? "e-m:e-i64:64-i128:128-n32:64-S128"
     58                              : "E-m:e-i64:64-i128:128-n32:64-S128")),
     59       FrameLowering(), InstrInfo(initializeSubtargetDependencies(FS)),
     60       TSInfo(&DL), TLInfo(TM) {}
     61 
     62 /// ClassifyGlobalReference - Find the target operand flags that describe
     63 /// how a global value should be referenced for the current subtarget.
     64 unsigned char
     65 AArch64Subtarget::ClassifyGlobalReference(const GlobalValue *GV,
     66                                         const TargetMachine &TM) const {
     67 
     68   // Determine whether this is a reference to a definition or a declaration.
     69   // Materializable GVs (in JIT lazy compilation mode) do not require an extra
     70   // load from stub.
     71   bool isDecl = GV->hasAvailableExternallyLinkage();
     72   if (GV->isDeclaration() && !GV->isMaterializable())
     73     isDecl = true;
     74 
     75   // MachO large model always goes via a GOT, simply to get a single 8-byte
     76   // absolute relocation on all global addresses.
     77   if (TM.getCodeModel() == CodeModel::Large && isTargetMachO())
     78     return AArch64II::MO_GOT;
     79 
     80   // The small code mode's direct accesses use ADRP, which cannot necessarily
     81   // produce the value 0 (if the code is above 4GB). Therefore they must use the
     82   // GOT.
     83   if (TM.getCodeModel() == CodeModel::Small && GV->isWeakForLinker() && isDecl)
     84     return AArch64II::MO_GOT;
     85 
     86   // If symbol visibility is hidden, the extra load is not needed if
     87   // the symbol is definitely defined in the current translation unit.
     88 
     89   // The handling of non-hidden symbols in PIC mode is rather target-dependent:
     90   //   + On MachO, if the symbol is defined in this module the GOT can be
     91   //     skipped.
     92   //   + On ELF, the R_AARCH64_COPY relocation means that even symbols actually
     93   //     defined could end up in unexpected places. Use a GOT.
     94   if (TM.getRelocationModel() != Reloc::Static && GV->hasDefaultVisibility()) {
     95     if (isTargetMachO())
     96       return (isDecl || GV->isWeakForLinker()) ? AArch64II::MO_GOT
     97                                                : AArch64II::MO_NO_FLAG;
     98     else
     99       // No need to go through the GOT for local symbols on ELF.
    100       return GV->hasLocalLinkage() ? AArch64II::MO_NO_FLAG : AArch64II::MO_GOT;
    101   }
    102 
    103   return AArch64II::MO_NO_FLAG;
    104 }
    105 
    106 /// This function returns the name of a function which has an interface
    107 /// like the non-standard bzero function, if such a function exists on
    108 /// the current subtarget and it is considered prefereable over
    109 /// memset with zero passed as the second argument. Otherwise it
    110 /// returns null.
    111 const char *AArch64Subtarget::getBZeroEntry() const {
    112   // Prefer bzero on Darwin only.
    113   if(isTargetDarwin())
    114     return "bzero";
    115 
    116   return nullptr;
    117 }
    118 
    119 void AArch64Subtarget::overrideSchedPolicy(MachineSchedPolicy &Policy,
    120                                          MachineInstr *begin, MachineInstr *end,
    121                                          unsigned NumRegionInstrs) const {
    122   // LNT run (at least on Cyclone) showed reasonably significant gains for
    123   // bi-directional scheduling. 253.perlbmk.
    124   Policy.OnlyTopDown = false;
    125   Policy.OnlyBottomUp = false;
    126 }
    127 
    128 bool AArch64Subtarget::enableEarlyIfConversion() const {
    129   return EnableEarlyIfConvert;
    130 }
    131