AArch64Subtarget.cpp revision dce4a407a24b04eebc6a376f8e62b41aaa7b071f 
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
21using 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
29static cl::opt<bool>
30EnableEarlyIfConvert("aarch64-early-ifcvt", cl::desc("Enable the early if "
31                     "converter pass"), cl::init(true), cl::Hidden);
32
33AArch64Subtarget::AArch64Subtarget(const std::string &TT,
34                                   const std::string &CPU,
35                                   const std::string &FS, bool LittleEndian)
36    : AArch64GenSubtargetInfo(TT, CPU, FS), ARMProcFamily(Others),
37      HasFPARMv8(false), HasNEON(false), HasCrypto(false), HasCRC(false),
38      HasZeroCycleRegMove(false), HasZeroCycleZeroing(false), CPUString(CPU),
39      TargetTriple(TT), IsLittleEndian(LittleEndian) {
40  // Determine default and user-specified characteristics
41
42  if (CPUString.empty())
43    CPUString = "generic";
44
45  ParseSubtargetFeatures(CPUString, FS);
46}
47
48/// ClassifyGlobalReference - Find the target operand flags that describe
49/// how a global value should be referenced for the current subtarget.
50unsigned char
51AArch64Subtarget::ClassifyGlobalReference(const GlobalValue *GV,
52                                        const TargetMachine &TM) const {
53
54  // Determine whether this is a reference to a definition or a declaration.
55  // Materializable GVs (in JIT lazy compilation mode) do not require an extra
56  // load from stub.
57  bool isDecl = GV->hasAvailableExternallyLinkage();
58  if (GV->isDeclaration() && !GV->isMaterializable())
59    isDecl = true;
60
61  // MachO large model always goes via a GOT, simply to get a single 8-byte
62  // absolute relocation on all global addresses.
63  if (TM.getCodeModel() == CodeModel::Large && isTargetMachO())
64    return AArch64II::MO_GOT;
65
66  // The small code mode's direct accesses use ADRP, which cannot necessarily
67  // produce the value 0 (if the code is above 4GB). Therefore they must use the
68  // GOT.
69  if (TM.getCodeModel() == CodeModel::Small && GV->isWeakForLinker() && isDecl)
70    return AArch64II::MO_GOT;
71
72  // If symbol visibility is hidden, the extra load is not needed if
73  // the symbol is definitely defined in the current translation unit.
74
75  // The handling of non-hidden symbols in PIC mode is rather target-dependent:
76  //   + On MachO, if the symbol is defined in this module the GOT can be
77  //     skipped.
78  //   + On ELF, the R_AARCH64_COPY relocation means that even symbols actually
79  //     defined could end up in unexpected places. Use a GOT.
80  if (TM.getRelocationModel() != Reloc::Static && GV->hasDefaultVisibility()) {
81    if (isTargetMachO())
82      return (isDecl || GV->isWeakForLinker()) ? AArch64II::MO_GOT
83                                               : AArch64II::MO_NO_FLAG;
84    else
85      // No need to go through the GOT for local symbols on ELF.
86      return GV->hasLocalLinkage() ? AArch64II::MO_NO_FLAG : AArch64II::MO_GOT;
87  }
88
89  return AArch64II::MO_NO_FLAG;
90}
91
92/// This function returns the name of a function which has an interface
93/// like the non-standard bzero function, if such a function exists on
94/// the current subtarget and it is considered prefereable over
95/// memset with zero passed as the second argument. Otherwise it
96/// returns null.
97const char *AArch64Subtarget::getBZeroEntry() const {
98  // Prefer bzero on Darwin only.
99  if(isTargetDarwin())
100    return "bzero";
101
102  return nullptr;
103}
104
105void AArch64Subtarget::overrideSchedPolicy(MachineSchedPolicy &Policy,
106                                         MachineInstr *begin, MachineInstr *end,
107                                         unsigned NumRegionInstrs) const {
108  // LNT run (at least on Cyclone) showed reasonably significant gains for
109  // bi-directional scheduling. 253.perlbmk.
110  Policy.OnlyTopDown = false;
111  Policy.OnlyBottomUp = false;
112}
113
114bool AArch64Subtarget::enableEarlyIfConversion() const {
115  return EnableEarlyIfConvert;
116}
117