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      1 //===-- SystemZMCObjectWriter.cpp - SystemZ ELF writer --------------------===//
      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 #include "MCTargetDesc/SystemZMCTargetDesc.h"
     11 #include "MCTargetDesc/SystemZMCFixups.h"
     12 #include "llvm/MC/MCELFObjectWriter.h"
     13 #include "llvm/MC/MCExpr.h"
     14 #include "llvm/MC/MCValue.h"
     15 
     16 using namespace llvm;
     17 
     18 namespace {
     19 class SystemZObjectWriter : public MCELFObjectTargetWriter {
     20 public:
     21   SystemZObjectWriter(uint8_t OSABI);
     22 
     23   virtual ~SystemZObjectWriter();
     24 
     25 protected:
     26   // Override MCELFObjectTargetWriter.
     27   unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
     28                         bool IsPCRel) const override;
     29 };
     30 } // end anonymous namespace
     31 
     32 SystemZObjectWriter::SystemZObjectWriter(uint8_t OSABI)
     33   : MCELFObjectTargetWriter(/*Is64Bit=*/true, OSABI, ELF::EM_S390,
     34                             /*HasRelocationAddend=*/ true) {}
     35 
     36 SystemZObjectWriter::~SystemZObjectWriter() {
     37 }
     38 
     39 // Return the relocation type for an absolute value of MCFixupKind Kind.
     40 static unsigned getAbsoluteReloc(unsigned Kind) {
     41   switch (Kind) {
     42   case FK_Data_1: return ELF::R_390_8;
     43   case FK_Data_2: return ELF::R_390_16;
     44   case FK_Data_4: return ELF::R_390_32;
     45   case FK_Data_8: return ELF::R_390_64;
     46   }
     47   llvm_unreachable("Unsupported absolute address");
     48 }
     49 
     50 // Return the relocation type for a PC-relative value of MCFixupKind Kind.
     51 static unsigned getPCRelReloc(unsigned Kind) {
     52   switch (Kind) {
     53   case FK_Data_2:                return ELF::R_390_PC16;
     54   case FK_Data_4:                return ELF::R_390_PC32;
     55   case FK_Data_8:                return ELF::R_390_PC64;
     56   case SystemZ::FK_390_PC16DBL:  return ELF::R_390_PC16DBL;
     57   case SystemZ::FK_390_PC32DBL:  return ELF::R_390_PC32DBL;
     58   case SystemZ::FK_390_PLT16DBL: return ELF::R_390_PLT16DBL;
     59   case SystemZ::FK_390_PLT32DBL: return ELF::R_390_PLT32DBL;
     60   }
     61   llvm_unreachable("Unsupported PC-relative address");
     62 }
     63 
     64 // Return the R_390_TLS_LE* relocation type for MCFixupKind Kind.
     65 static unsigned getTLSLEReloc(unsigned Kind) {
     66   switch (Kind) {
     67   case FK_Data_4: return ELF::R_390_TLS_LE32;
     68   case FK_Data_8: return ELF::R_390_TLS_LE64;
     69   }
     70   llvm_unreachable("Unsupported absolute address");
     71 }
     72 
     73 // Return the PLT relocation counterpart of MCFixupKind Kind.
     74 static unsigned getPLTReloc(unsigned Kind) {
     75   switch (Kind) {
     76   case SystemZ::FK_390_PC16DBL: return ELF::R_390_PLT16DBL;
     77   case SystemZ::FK_390_PC32DBL: return ELF::R_390_PLT32DBL;
     78   }
     79   llvm_unreachable("Unsupported absolute address");
     80 }
     81 
     82 unsigned SystemZObjectWriter::GetRelocType(const MCValue &Target,
     83                                            const MCFixup &Fixup,
     84                                            bool IsPCRel) const {
     85   MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant();
     86   unsigned Kind = Fixup.getKind();
     87   switch (Modifier) {
     88   case MCSymbolRefExpr::VK_None:
     89     if (IsPCRel)
     90       return getPCRelReloc(Kind);
     91     return getAbsoluteReloc(Kind);
     92 
     93   case MCSymbolRefExpr::VK_NTPOFF:
     94     assert(!IsPCRel && "NTPOFF shouldn't be PC-relative");
     95     return getTLSLEReloc(Kind);
     96 
     97   case MCSymbolRefExpr::VK_GOT:
     98     if (IsPCRel && Kind == SystemZ::FK_390_PC32DBL)
     99       return ELF::R_390_GOTENT;
    100     llvm_unreachable("Only PC-relative GOT accesses are supported for now");
    101 
    102   case MCSymbolRefExpr::VK_PLT:
    103     assert(IsPCRel && "@PLT shouldt be PC-relative");
    104     return getPLTReloc(Kind);
    105 
    106   default:
    107     llvm_unreachable("Modifier not supported");
    108   }
    109 }
    110 
    111 MCObjectWriter *llvm::createSystemZObjectWriter(raw_ostream &OS,
    112                                                 uint8_t OSABI) {
    113   MCELFObjectTargetWriter *MOTW = new SystemZObjectWriter(OSABI);
    114   return createELFObjectWriter(MOTW, OS, /*IsLittleEndian=*/false);
    115 }
    116