LLVM  7.0.0svn
PPCAsmBackend.cpp
Go to the documentation of this file.
1 //===-- PPCAsmBackend.cpp - PPC Assembler Backend -------------------------===//
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 
12 #include "llvm/BinaryFormat/ELF.h"
14 #include "llvm/MC/MCAsmBackend.h"
15 #include "llvm/MC/MCAssembler.h"
19 #include "llvm/MC/MCObjectWriter.h"
20 #include "llvm/MC/MCSectionMachO.h"
22 #include "llvm/MC/MCSymbolELF.h"
23 #include "llvm/MC/MCValue.h"
26 using namespace llvm;
27 
28 static uint64_t adjustFixupValue(unsigned Kind, uint64_t Value) {
29  switch (Kind) {
30  default:
31  llvm_unreachable("Unknown fixup kind!");
32  case FK_Data_1:
33  case FK_Data_2:
34  case FK_Data_4:
35  case FK_Data_8:
37  return Value;
40  return Value & 0xfffc;
43  return Value & 0x3fffffc;
45  return Value & 0xffff;
47  return Value & 0xfffc;
48  }
49 }
50 
51 static unsigned getFixupKindNumBytes(unsigned Kind) {
52  switch (Kind) {
53  default:
54  llvm_unreachable("Unknown fixup kind!");
55  case FK_Data_1:
56  return 1;
57  case FK_Data_2:
60  return 2;
61  case FK_Data_4:
66  return 4;
67  case FK_Data_8:
68  return 8;
70  return 0;
71  }
72 }
73 
74 namespace {
75 
76 class PPCAsmBackend : public MCAsmBackend {
77  const Target &TheTarget;
78  bool IsLittleEndian;
79 public:
80  PPCAsmBackend(const Target &T, bool isLittle) : MCAsmBackend(), TheTarget(T),
81  IsLittleEndian(isLittle) {}
82 
83  unsigned getNumFixupKinds() const override {
85  }
86 
87  const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override {
88  const static MCFixupKindInfo InfosBE[PPC::NumTargetFixupKinds] = {
89  // name offset bits flags
90  { "fixup_ppc_br24", 6, 24, MCFixupKindInfo::FKF_IsPCRel },
91  { "fixup_ppc_brcond14", 16, 14, MCFixupKindInfo::FKF_IsPCRel },
92  { "fixup_ppc_br24abs", 6, 24, 0 },
93  { "fixup_ppc_brcond14abs", 16, 14, 0 },
94  { "fixup_ppc_half16", 0, 16, 0 },
95  { "fixup_ppc_half16ds", 0, 14, 0 },
96  { "fixup_ppc_nofixup", 0, 0, 0 }
97  };
98  const static MCFixupKindInfo InfosLE[PPC::NumTargetFixupKinds] = {
99  // name offset bits flags
100  { "fixup_ppc_br24", 2, 24, MCFixupKindInfo::FKF_IsPCRel },
101  { "fixup_ppc_brcond14", 2, 14, MCFixupKindInfo::FKF_IsPCRel },
102  { "fixup_ppc_br24abs", 2, 24, 0 },
103  { "fixup_ppc_brcond14abs", 2, 14, 0 },
104  { "fixup_ppc_half16", 0, 16, 0 },
105  { "fixup_ppc_half16ds", 2, 14, 0 },
106  { "fixup_ppc_nofixup", 0, 0, 0 }
107  };
108 
109  if (Kind < FirstTargetFixupKind)
110  return MCAsmBackend::getFixupKindInfo(Kind);
111 
112  assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
113  "Invalid kind!");
114  return (IsLittleEndian? InfosLE : InfosBE)[Kind - FirstTargetFixupKind];
115  }
116 
117  void applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
119  uint64_t Value, bool IsResolved) const override {
120  Value = adjustFixupValue(Fixup.getKind(), Value);
121  if (!Value) return; // Doesn't change encoding.
122 
123  unsigned Offset = Fixup.getOffset();
124  unsigned NumBytes = getFixupKindNumBytes(Fixup.getKind());
125 
126  // For each byte of the fragment that the fixup touches, mask in the bits
127  // from the fixup value. The Value has been "split up" into the appropriate
128  // bitfields above.
129  for (unsigned i = 0; i != NumBytes; ++i) {
130  unsigned Idx = IsLittleEndian ? i : (NumBytes - 1 - i);
131  Data[Offset + i] |= uint8_t((Value >> (Idx * 8)) & 0xff);
132  }
133  }
134 
135  bool shouldForceRelocation(const MCAssembler &Asm, const MCFixup &Fixup,
136  const MCValue &Target) override {
137  switch ((PPC::Fixups)Fixup.getKind()) {
138  default:
139  return false;
140  case PPC::fixup_ppc_br24:
142  // If the target symbol has a local entry point we must not attempt
143  // to resolve the fixup directly. Emit a relocation and leave
144  // resolution of the final target address to the linker.
145  if (const MCSymbolRefExpr *A = Target.getSymA()) {
146  if (const auto *S = dyn_cast<MCSymbolELF>(&A->getSymbol())) {
147  // The "other" values are stored in the last 6 bits of the second
148  // byte. The traditional defines for STO values assume the full byte
149  // and thus the shift to pack it.
150  unsigned Other = S->getOther() << 2;
151  if ((Other & ELF::STO_PPC64_LOCAL_MASK) != 0)
152  return true;
153  }
154  }
155  return false;
156  }
157  }
158 
159  bool mayNeedRelaxation(const MCInst &Inst) const override {
160  // FIXME.
161  return false;
162  }
163 
164  bool fixupNeedsRelaxation(const MCFixup &Fixup,
165  uint64_t Value,
166  const MCRelaxableFragment *DF,
167  const MCAsmLayout &Layout) const override {
168  // FIXME.
169  llvm_unreachable("relaxInstruction() unimplemented");
170  }
171 
172  void relaxInstruction(const MCInst &Inst, const MCSubtargetInfo &STI,
173  MCInst &Res) const override {
174  // FIXME.
175  llvm_unreachable("relaxInstruction() unimplemented");
176  }
177 
178  bool writeNopData(uint64_t Count, MCObjectWriter *OW) const override {
179  uint64_t NumNops = Count / 4;
180  for (uint64_t i = 0; i != NumNops; ++i)
181  OW->write32(0x60000000);
182 
183  OW->WriteZeros(Count % 4);
184 
185  return true;
186  }
187 
188  unsigned getPointerSize() const {
189  StringRef Name = TheTarget.getName();
190  if (Name == "ppc64" || Name == "ppc64le") return 8;
191  assert(Name == "ppc32" && "Unknown target name!");
192  return 4;
193  }
194 
195  bool isLittleEndian() const {
196  return IsLittleEndian;
197  }
198 };
199 } // end anonymous namespace
200 
201 
202 // FIXME: This should be in a separate file.
203 namespace {
204  class DarwinPPCAsmBackend : public PPCAsmBackend {
205  public:
206  DarwinPPCAsmBackend(const Target &T) : PPCAsmBackend(T, false) { }
207 
208  std::unique_ptr<MCObjectWriter>
209  createObjectWriter(raw_pwrite_stream &OS) const override {
210  bool is64 = getPointerSize() == 8;
212  OS,
213  /*Is64Bit=*/is64,
216  }
217  };
218 
219  class ELFPPCAsmBackend : public PPCAsmBackend {
220  uint8_t OSABI;
221  public:
222  ELFPPCAsmBackend(const Target &T, bool IsLittleEndian, uint8_t OSABI) :
223  PPCAsmBackend(T, IsLittleEndian), OSABI(OSABI) { }
224 
225  std::unique_ptr<MCObjectWriter>
226  createObjectWriter(raw_pwrite_stream &OS) const override {
227  bool is64 = getPointerSize() == 8;
228  return createPPCELFObjectWriter(OS, is64, isLittleEndian(), OSABI);
229  }
230  };
231 
232 } // end anonymous namespace
233 
235  const MCSubtargetInfo &STI,
236  const MCRegisterInfo &MRI,
237  const MCTargetOptions &Options) {
238  const Triple &TT = STI.getTargetTriple();
239  if (TT.isOSDarwin())
240  return new DarwinPPCAsmBackend(T);
241 
242  uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TT.getOS());
243  bool IsLittleEndian = TT.getArch() == Triple::ppc64le;
244  return new ELFPPCAsmBackend(T, IsLittleEndian, OSABI);
245 }
bool isOSDarwin() const
isOSDarwin - Is this a "Darwin" OS (OS X, iOS, or watchOS).
Definition: Triple.h:470
void WriteZeros(unsigned N)
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
This represents an "assembler immediate".
Definition: MCValue.h:40
OSType getOS() const
getOS - Get the parsed operating system type of this triple.
Definition: Triple.h:294
virtual const MCFixupKindInfo & getFixupKindInfo(MCFixupKind Kind) const
Get information on a fixup kind.
14-bit absolute relocation for conditional branches.
Definition: PPCFixupKinds.h:30
Defines the object file and target independent interfaces used by the assembler backend to write nati...
Encode information on a single operation to perform on a byte sequence (e.g., an encoded instruction)...
Definition: MCFixup.h:66
const Triple & getTargetTriple() const
getTargetTriple - Return the target triple string.
Is this fixup kind PCrelative? This is used by the assembler backend to evaluate fixup values in a ta...
const char * getName() const
getName - Get the target name.
A 16-bit fixup corresponding to lo16(_foo) or ha16(_foo) for instrs like &#39;li&#39; or &#39;addis&#39;.
Definition: PPCFixupKinds.h:34
24-bit absolute relocation for direct branches like &#39;ba&#39; and &#39;bla&#39;.
Definition: PPCFixupKinds.h:27
Encapsulates the layout of an assembly file at a particular point in time.
Definition: MCAsmLayout.h:29
Not a true fixup, but ties a symbol to a call to __tls_get_addr for the TLS general and local dynamic...
Definition: PPCFixupKinds.h:43
Represent a reference to a symbol from inside an expression.
Definition: MCExpr.h:165
ELFYAML::ELF_STO Other
Definition: ELFYAML.cpp:766
A four-byte fixup.
Definition: MCFixup.h:26
std::unique_ptr< MCObjectWriter > createPPCMachObjectWriter(raw_pwrite_stream &OS, bool Is64Bit, uint32_t CPUType, uint32_t CPUSubtype)
Construct a PPC Mach-O object writer.
ArchType getArch() const
getArch - Get the parsed architecture type of this triple.
Definition: Triple.h:285
static unsigned getFixupKindNumBytes(unsigned Kind)
Instances of this class represent a single low-level machine instruction.
Definition: MCInst.h:159
MCRegisterInfo base class - We assume that the target defines a static array of MCRegisterDesc object...
A relaxable fragment holds on to its MCInst, since it may need to be relaxed during the assembler lay...
Definition: MCFragment.h:257
void write32(uint32_t Value)
unsigned const MachineRegisterInfo * MRI
MutableArrayRef - Represent a mutable reference to an array (0 or more elements consecutively in memo...
Definition: ArrayRef.h:291
MCFixupKind
Extensible enumeration to represent the type of a fixup.
Definition: MCFixup.h:23
const MCSymbolRefExpr * getSymA() const
Definition: MCValue.h:48
MCAsmBackend * createPPCAsmBackend(const Target &T, const MCSubtargetInfo &STI, const MCRegisterInfo &MRI, const MCTargetOptions &Options)
uint32_t getOffset() const
Definition: MCFixup.h:95
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
A one-byte fixup.
Definition: MCFixup.h:24
Triple - Helper class for working with autoconf configuration names.
Definition: Triple.h:44
PowerPC TLS Dynamic Call Fixup
std::unique_ptr< MCObjectWriter > createPPCELFObjectWriter(raw_pwrite_stream &OS, bool Is64Bit, bool IsLittleEndian, uint8_t OSABI)
Construct an PPC ELF object writer.
Target - Wrapper for Target specific information.
A 14-bit fixup corresponding to lo16(_foo) with implied 2 zero bits for instrs like &#39;std&#39;...
Definition: PPCFixupKinds.h:38
MCSubtargetInfo - Generic base class for all target subtargets.
A eight-byte fixup.
Definition: MCFixup.h:27
Target independent information on a fixup kind.
An abstract base class for streams implementations that also support a pwrite operation.
Definition: raw_ostream.h:337
const unsigned Kind
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
LLVM Value Representation.
Definition: Value.h:73
Generic interface to target specific assembler backends.
Definition: MCAsmBackend.h:40
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:49
static uint64_t adjustFixupValue(unsigned Kind, uint64_t Value)
14-bit PC relative relocation for conditional branches.
Definition: PPCFixupKinds.h:24
static uint64_t getPointerSize(const Value *V, const DataLayout &DL, const TargetLibraryInfo &TLI)
A two-byte fixup.
Definition: MCFixup.h:25
MCFixupKind getKind() const
Definition: MCFixup.h:93