llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCAsmBackend.cpp

   1 //===-- SystemZMCAsmBackend.cpp - SystemZ assembler backend ---------------===//
   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 #include "MCTargetDesc/SystemZMCFixups.h"
  10 #include "MCTargetDesc/SystemZMCTargetDesc.h"
  11 #include "llvm/ADT/StringSwitch.h"
  12 #include "llvm/MC/MCAsmBackend.h"
  13 #include "llvm/MC/MCELFObjectWriter.h"
  14 #include "llvm/MC/MCFixupKindInfo.h"
  15 #include "llvm/MC/MCInst.h"
  16 #include "llvm/MC/MCObjectWriter.h"
  17 #include "llvm/MC/MCSubtargetInfo.h"
  18
  19 using namespace llvm;
  20
  21 // Value is a fully-resolved relocation value: Symbol + Addend [- Pivot].
  22 // Return the bits that should be installed in a relocation field for
  23 // fixup kind Kind.
  24 static uint64_t extractBitsForFixup(MCFixupKind Kind, uint64_t Value) {
  25   if (Kind < FirstTargetFixupKind)
  26     return Value;
  27
  28   switch (unsigned(Kind)) {
  29   case SystemZ::FK_390_PC12DBL:
  30   case SystemZ::FK_390_PC16DBL:
  31   case SystemZ::FK_390_PC24DBL:
  32   case SystemZ::FK_390_PC32DBL:
  33     return (int64_t)Value / 2;
  34
  35   case SystemZ::FK_390_TLS_CALL:
  36     return 0;
  37   }
  38
  39   llvm_unreachable("Unknown fixup kind!");
  40 }
  41
  42 namespace {
  43 class SystemZMCAsmBackend : public MCAsmBackend {
  44   uint8_t OSABI;
  45 public:
  46   SystemZMCAsmBackend(uint8_t osABI)
  47       : MCAsmBackend(support::big), OSABI(osABI) {}
  48
  49   // Override MCAsmBackend
  50   unsigned getNumFixupKinds() const override {
  51     return SystemZ::NumTargetFixupKinds;
  52   }
  53   Optional<MCFixupKind> getFixupKind(StringRef Name) const override;
  54   const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override;
  55   bool shouldForceRelocation(const MCAssembler &Asm, const MCFixup &Fixup,
  56                              const MCValue &Target) override;
  57   void applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
  58                   const MCValue &Target, MutableArrayRef<char> Data,
  59                   uint64_t Value, bool IsResolved,
  60                   const MCSubtargetInfo *STI) const override;
  61   bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
  62                             const MCRelaxableFragment *Fragment,
  63                             const MCAsmLayout &Layout) const override {
  64     return false;
  65   }
  66   bool writeNopData(raw_ostream &OS, uint64_t Count) const override;
  67   std::unique_ptr<MCObjectTargetWriter>
  68   createObjectTargetWriter() const override {
  69     return createSystemZObjectWriter(OSABI);
  70   }
  71 };
  72 } // end anonymous namespace
  73
  74 Optional<MCFixupKind> SystemZMCAsmBackend::getFixupKind(StringRef Name) const {
  75   unsigned Type = llvm::StringSwitch<unsigned>(Name)
  76 #define ELF_RELOC(X, Y) .Case(#X, Y)
  77 #include "llvm/BinaryFormat/ELFRelocs/SystemZ.def"
  78 #undef ELF_RELOC
  79                         .Case("BFD_RELOC_NONE", ELF::R_390_NONE)
  80                         .Case("BFD_RELOC_8", ELF::R_390_8)
  81                         .Case("BFD_RELOC_16", ELF::R_390_16)
  82                         .Case("BFD_RELOC_32", ELF::R_390_32)
  83                         .Case("BFD_RELOC_64", ELF::R_390_64)
  84                         .Default(-1u);
  85   if (Type != -1u)
  86     return static_cast<MCFixupKind>(FirstLiteralRelocationKind + Type);
  87   return None;
  88 }
  89
  90 const MCFixupKindInfo &
  91 SystemZMCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
  92   const static MCFixupKindInfo Infos[SystemZ::NumTargetFixupKinds] = {
  93     { "FK_390_PC12DBL",  4, 12, MCFixupKindInfo::FKF_IsPCRel },
  94     { "FK_390_PC16DBL",  0, 16, MCFixupKindInfo::FKF_IsPCRel },
  95     { "FK_390_PC24DBL",  0, 24, MCFixupKindInfo::FKF_IsPCRel },
  96     { "FK_390_PC32DBL",  0, 32, MCFixupKindInfo::FKF_IsPCRel },
  97     { "FK_390_TLS_CALL", 0, 0, 0 }
  98   };
  99
 100   // Fixup kinds from .reloc directive are like R_390_NONE. They
 101   // do not require any extra processing.
 102   if (Kind >= FirstLiteralRelocationKind)
 103     return MCAsmBackend::getFixupKindInfo(FK_NONE);
 104
 105   if (Kind < FirstTargetFixupKind)
 106     return MCAsmBackend::getFixupKindInfo(Kind);
 107
 108   assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
 109          "Invalid kind!");
 110   return Infos[Kind - FirstTargetFixupKind];
 111 }
 112
 113 bool SystemZMCAsmBackend::shouldForceRelocation(const MCAssembler &,
 114                                                 const MCFixup &Fixup,
 115                                                 const MCValue &) {
 116   return Fixup.getKind() >= FirstLiteralRelocationKind;
 117 }
 118
 119 void SystemZMCAsmBackend::applyFixup(const MCAssembler &Asm,
 120                                      const MCFixup &Fixup,
 121                                      const MCValue &Target,
 122                                      MutableArrayRef<char> Data, uint64_t Value,
 123                                      bool IsResolved,
 124                                      const MCSubtargetInfo *STI) const {
 125   MCFixupKind Kind = Fixup.getKind();
 126   if (Kind >= FirstLiteralRelocationKind)
 127     return;
 128   unsigned Offset = Fixup.getOffset();
 129   unsigned BitSize = getFixupKindInfo(Kind).TargetSize;
 130   unsigned Size = (BitSize + 7) / 8;
 131
 132   assert(Offset + Size <= Data.size() && "Invalid fixup offset!");
 133
 134   // Big-endian insertion of Size bytes.
 135   Value = extractBitsForFixup(Kind, Value);
 136   if (BitSize < 64)
 137     Value &= ((uint64_t)1 << BitSize) - 1;
 138   unsigned ShiftValue = (Size * 8) - 8;
 139   for (unsigned I = 0; I != Size; ++I) {
 140     Data[Offset + I] |= uint8_t(Value >> ShiftValue);
 141     ShiftValue -= 8;
 142   }
 143 }
 144
 145 bool SystemZMCAsmBackend::writeNopData(raw_ostream &OS, uint64_t Count) const {
 146   for (uint64_t I = 0; I != Count; ++I)
 147     OS << '\x7';
 148   return true;
 149 }
 150
 151 MCAsmBackend *llvm::createSystemZMCAsmBackend(const Target &T,
 152                                               const MCSubtargetInfo &STI,
 153                                               const MCRegisterInfo &MRI,
 154                                               const MCTargetOptions &Options) {
 155   uint8_t OSABI =
 156       MCELFObjectTargetWriter::getOSABI(STI.getTargetTriple().getOS());
 157   return new SystemZMCAsmBackend(OSABI);
 158 }