1 //===-- SystemZMCAsmBackend.cpp - SystemZ 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 
10 #include "MCTargetDesc/SystemZMCFixups.h"
11 #include "MCTargetDesc/SystemZMCTargetDesc.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 
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     : 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) const override;
56   bool mayNeedRelaxation(const MCInst &Inst) const override {
57     return false;
58   }
59   bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
60                             const MCRelaxableFragment *Fragment,
61                             const MCAsmLayout &Layout) const override {
62     return false;
63   }
64   void relaxInstruction(const MCInst &Inst, const MCSubtargetInfo &STI,
65                         MCInst &Res) const override {
66     llvm_unreachable("SystemZ does do not have assembler relaxation");
67   }
68   bool writeNopData(uint64_t Count, MCObjectWriter *OW) const override;
69   MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
70     return createSystemZObjectWriter(OS, OSABI);
71   }
72 };
73 } // end anonymous namespace
74 
75 const MCFixupKindInfo &
76 SystemZMCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
77   const static MCFixupKindInfo Infos[SystemZ::NumTargetFixupKinds] = {
78     { "FK_390_PC12DBL",  4, 12, MCFixupKindInfo::FKF_IsPCRel },
79     { "FK_390_PC16DBL",  0, 16, MCFixupKindInfo::FKF_IsPCRel },
80     { "FK_390_PC24DBL",  0, 24, MCFixupKindInfo::FKF_IsPCRel },
81     { "FK_390_PC32DBL",  0, 32, MCFixupKindInfo::FKF_IsPCRel },
82     { "FK_390_TLS_CALL", 0, 0, 0 }
83   };
84 
85   if (Kind < FirstTargetFixupKind)
86     return MCAsmBackend::getFixupKindInfo(Kind);
87 
88   assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
89          "Invalid kind!");
90   return Infos[Kind - FirstTargetFixupKind];
91 }
92 
93 void SystemZMCAsmBackend::applyFixup(const MCAssembler &Asm,
94                                      const MCFixup &Fixup,
95                                      const MCValue &Target,
96                                      MutableArrayRef<char> Data, uint64_t Value,
97                                      bool IsResolved) const {
98   MCFixupKind Kind = Fixup.getKind();
99   unsigned Offset = Fixup.getOffset();
100   unsigned BitSize = getFixupKindInfo(Kind).TargetSize;
101   unsigned Size = (BitSize + 7) / 8;
102 
103   assert(Offset + Size <= Data.size() && "Invalid fixup offset!");
104 
105   // Big-endian insertion of Size bytes.
106   Value = extractBitsForFixup(Kind, Value);
107   if (BitSize < 64)
108     Value &= ((uint64_t)1 << BitSize) - 1;
109   unsigned ShiftValue = (Size * 8) - 8;
110   for (unsigned I = 0; I != Size; ++I) {
111     Data[Offset + I] |= uint8_t(Value >> ShiftValue);
112     ShiftValue -= 8;
113   }
114 }
115 
116 bool SystemZMCAsmBackend::writeNopData(uint64_t Count,
117                                        MCObjectWriter *OW) const {
118   for (uint64_t I = 0; I != Count; ++I)
119     OW->write8(7);
120   return true;
121 }
122 
123 MCAsmBackend *llvm::createSystemZMCAsmBackend(const Target &T,
124                                               const MCRegisterInfo &MRI,
125                                               const Triple &TT, StringRef CPU,
126                                               const MCTargetOptions &Options) {
127   uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TT.getOS());
128   return new SystemZMCAsmBackend(OSABI);
129 }
130