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/MC/MCAsmBackend.h"
  12 #include "llvm/MC/MCELFObjectWriter.h"
  13 #include "llvm/MC/MCFixupKindInfo.h"
  14 #include "llvm/MC/MCInst.h"
  15 #include "llvm/MC/MCObjectWriter.h"
  16 #include "llvm/MC/MCSubtargetInfo.h"
  17
  18 using namespace llvm;
  19
  20 // Value is a fully-resolved relocation value: Symbol + Addend [- Pivot].
  21 // Return the bits that should be installed in a relocation field for
  22 // fixup kind Kind.
  23 static uint64_t extractBitsForFixup(MCFixupKind Kind, uint64_t Value) {
  24   if (Kind < FirstTargetFixupKind)
  25     return Value;
  26
  27   switch (unsigned(Kind)) {
  28   case SystemZ::FK_390_PC12DBL:
  29   case SystemZ::FK_390_PC16DBL:
  30   case SystemZ::FK_390_PC24DBL:
  31   case SystemZ::FK_390_PC32DBL:
  32     return (int64_t)Value / 2;
  33
  34   case SystemZ::FK_390_TLS_CALL:
  35     return 0;
  36   }
  37
  38   llvm_unreachable("Unknown fixup kind!");
  39 }
  40
  41 namespace {
  42 class SystemZMCAsmBackend : public MCAsmBackend {
  43   uint8_t OSABI;
  44 public:
  45   SystemZMCAsmBackend(uint8_t osABI)
  46       : MCAsmBackend(support::big), OSABI(osABI) {}
  47
  48   // Override MCAsmBackend
  49   unsigned getNumFixupKinds() const override {
  50     return SystemZ::NumTargetFixupKinds;
  51   }
  52   const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override;
  53   void applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
  54                   const MCValue &Target, MutableArrayRef<char> Data,
  55                   uint64_t Value, bool IsResolved,
  56                   const MCSubtargetInfo *STI) const override;
  57   bool mayNeedRelaxation(const MCInst &Inst,
  58                          const MCSubtargetInfo &STI) const override {
  59     return false;
  60   }
  61   bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
  62                             const MCRelaxableFragment *Fragment,
  63                             const MCAsmLayout &Layout) const override {
  64     return false;
  65   }
  66   void relaxInstruction(const MCInst &Inst, const MCSubtargetInfo &STI,
  67                         MCInst &Res) const override {
  68     llvm_unreachable("SystemZ does do not have assembler relaxation");
  69   }
  70   bool writeNopData(raw_ostream &OS, uint64_t Count) const override;
  71   std::unique_ptr<MCObjectTargetWriter>
  72   createObjectTargetWriter() const override {
  73     return createSystemZObjectWriter(OSABI);
  74   }
  75 };
  76 } // end anonymous namespace
  77
  78 const MCFixupKindInfo &
  79 SystemZMCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
  80   const static MCFixupKindInfo Infos[SystemZ::NumTargetFixupKinds] = {
  81     { "FK_390_PC12DBL",  4, 12, MCFixupKindInfo::FKF_IsPCRel },
  82     { "FK_390_PC16DBL",  0, 16, MCFixupKindInfo::FKF_IsPCRel },
  83     { "FK_390_PC24DBL",  0, 24, MCFixupKindInfo::FKF_IsPCRel },
  84     { "FK_390_PC32DBL",  0, 32, MCFixupKindInfo::FKF_IsPCRel },
  85     { "FK_390_TLS_CALL", 0, 0, 0 }
  86   };
  87
  88   if (Kind < FirstTargetFixupKind)
  89     return MCAsmBackend::getFixupKindInfo(Kind);
  90
  91   assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
  92          "Invalid kind!");
  93   return Infos[Kind - FirstTargetFixupKind];
  94 }
  95
  96 void SystemZMCAsmBackend::applyFixup(const MCAssembler &Asm,
  97                                      const MCFixup &Fixup,
  98                                      const MCValue &Target,
  99                                      MutableArrayRef<char> Data, uint64_t Value,
 100                                      bool IsResolved,
 101                                      const MCSubtargetInfo *STI) const {
 102   MCFixupKind Kind = Fixup.getKind();
 103   unsigned Offset = Fixup.getOffset();
 104   unsigned BitSize = getFixupKindInfo(Kind).TargetSize;
 105   unsigned Size = (BitSize + 7) / 8;
 106
 107   assert(Offset + Size <= Data.size() && "Invalid fixup offset!");
 108
 109   // Big-endian insertion of Size bytes.
 110   Value = extractBitsForFixup(Kind, Value);
 111   if (BitSize < 64)
 112     Value &= ((uint64_t)1 << BitSize) - 1;
 113   unsigned ShiftValue = (Size * 8) - 8;
 114   for (unsigned I = 0; I != Size; ++I) {
 115     Data[Offset + I] |= uint8_t(Value >> ShiftValue);
 116     ShiftValue -= 8;
 117   }
 118 }
 119
 120 bool SystemZMCAsmBackend::writeNopData(raw_ostream &OS, uint64_t Count) const {
 121   for (uint64_t I = 0; I != Count; ++I)
 122     OS << '\x7';
 123   return true;
 124 }
 125
 126 MCAsmBackend *llvm::createSystemZMCAsmBackend(const Target &T,
 127                                               const MCSubtargetInfo &STI,
 128                                               const MCRegisterInfo &MRI,
 129                                               const MCTargetOptions &Options) {
 130   uint8_t OSABI =
 131       MCELFObjectTargetWriter::getOSABI(STI.getTargetTriple().getOS());
 132   return new SystemZMCAsmBackend(OSABI);
 133 }