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 }
134