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/MCAssembler.h"
14 #include "llvm/MC/MCContext.h"
15 #include "llvm/MC/MCELFObjectWriter.h"
16 #include "llvm/MC/MCFixupKindInfo.h"
17 #include "llvm/MC/MCInst.h"
18 #include "llvm/MC/MCObjectWriter.h"
19 #include "llvm/MC/MCSubtargetInfo.h"
20
21 using namespace llvm;
22
23 // Value is a fully-resolved relocation value: Symbol + Addend [- Pivot].
24 // Return the bits that should be installed in a relocation field for
25 // fixup kind Kind.
extractBitsForFixup(MCFixupKind Kind,uint64_t Value,const MCFixup & Fixup,MCContext & Ctx)26 static uint64_t extractBitsForFixup(MCFixupKind Kind, uint64_t Value,
27 const MCFixup &Fixup, MCContext &Ctx) {
28 if (Kind < FirstTargetFixupKind)
29 return Value;
30
31 auto checkFixupInRange = [&](int64_t Min, int64_t Max) -> bool {
32 int64_t SVal = int64_t(Value);
33 if (SVal < Min || SVal > Max) {
34 Ctx.reportError(Fixup.getLoc(), "operand out of range (" + Twine(SVal) +
35 " not between " + Twine(Min) +
36 " and " + Twine(Max) + ")");
37 return false;
38 }
39 return true;
40 };
41
42 auto handlePCRelFixupValue = [&](unsigned W) -> uint64_t {
43 if (Value % 2 != 0)
44 Ctx.reportError(Fixup.getLoc(), "Non-even PC relative offset.");
45 if (!checkFixupInRange(minIntN(W) * 2, maxIntN(W) * 2))
46 return 0;
47 return (int64_t)Value / 2;
48 };
49
50 switch (unsigned(Kind)) {
51 case SystemZ::FK_390_PC12DBL:
52 return handlePCRelFixupValue(12);
53 case SystemZ::FK_390_PC16DBL:
54 return handlePCRelFixupValue(16);
55 case SystemZ::FK_390_PC24DBL:
56 return handlePCRelFixupValue(24);
57 case SystemZ::FK_390_PC32DBL:
58 return handlePCRelFixupValue(32);
59
60 case SystemZ::FK_390_12:
61 if (!checkFixupInRange(0, maxUIntN(12)))
62 return 0;
63 return Value;
64
65 case SystemZ::FK_390_20: {
66 if (!checkFixupInRange(minIntN(20), maxIntN(20)))
67 return 0;
68 // The high byte of a 20 bit displacement value comes first.
69 uint64_t DLo = Value & 0xfff;
70 uint64_t DHi = (Value >> 12) & 0xff;
71 return (DLo << 8) | DHi;
72 }
73
74 case SystemZ::FK_390_TLS_CALL:
75 return 0;
76 }
77
78 llvm_unreachable("Unknown fixup kind!");
79 }
80
81 namespace {
82 class SystemZMCAsmBackend : public MCAsmBackend {
83 uint8_t OSABI;
84 public:
SystemZMCAsmBackend(uint8_t osABI)85 SystemZMCAsmBackend(uint8_t osABI)
86 : MCAsmBackend(support::big), OSABI(osABI) {}
87
88 // Override MCAsmBackend
getNumFixupKinds() const89 unsigned getNumFixupKinds() const override {
90 return SystemZ::NumTargetFixupKinds;
91 }
92 std::optional<MCFixupKind> getFixupKind(StringRef Name) const override;
93 const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override;
94 bool shouldForceRelocation(const MCAssembler &Asm, const MCFixup &Fixup,
95 const MCValue &Target) override;
96 void applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
97 const MCValue &Target, MutableArrayRef<char> Data,
98 uint64_t Value, bool IsResolved,
99 const MCSubtargetInfo *STI) const override;
fixupNeedsRelaxation(const MCFixup & Fixup,uint64_t Value,const MCRelaxableFragment * Fragment,const MCAsmLayout & Layout) const100 bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
101 const MCRelaxableFragment *Fragment,
102 const MCAsmLayout &Layout) const override {
103 return false;
104 }
105 bool writeNopData(raw_ostream &OS, uint64_t Count,
106 const MCSubtargetInfo *STI) const override;
107 std::unique_ptr<MCObjectTargetWriter>
createObjectTargetWriter() const108 createObjectTargetWriter() const override {
109 return createSystemZObjectWriter(OSABI);
110 }
111 };
112 } // end anonymous namespace
113
114 std::optional<MCFixupKind>
getFixupKind(StringRef Name) const115 SystemZMCAsmBackend::getFixupKind(StringRef Name) const {
116 unsigned Type = llvm::StringSwitch<unsigned>(Name)
117 #define ELF_RELOC(X, Y) .Case(#X, Y)
118 #include "llvm/BinaryFormat/ELFRelocs/SystemZ.def"
119 #undef ELF_RELOC
120 .Case("BFD_RELOC_NONE", ELF::R_390_NONE)
121 .Case("BFD_RELOC_8", ELF::R_390_8)
122 .Case("BFD_RELOC_16", ELF::R_390_16)
123 .Case("BFD_RELOC_32", ELF::R_390_32)
124 .Case("BFD_RELOC_64", ELF::R_390_64)
125 .Default(-1u);
126 if (Type != -1u)
127 return static_cast<MCFixupKind>(FirstLiteralRelocationKind + Type);
128 return std::nullopt;
129 }
130
131 const MCFixupKindInfo &
getFixupKindInfo(MCFixupKind Kind) const132 SystemZMCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
133 const static MCFixupKindInfo Infos[SystemZ::NumTargetFixupKinds] = {
134 { "FK_390_PC12DBL", 4, 12, MCFixupKindInfo::FKF_IsPCRel },
135 { "FK_390_PC16DBL", 0, 16, MCFixupKindInfo::FKF_IsPCRel },
136 { "FK_390_PC24DBL", 0, 24, MCFixupKindInfo::FKF_IsPCRel },
137 { "FK_390_PC32DBL", 0, 32, MCFixupKindInfo::FKF_IsPCRel },
138 { "FK_390_TLS_CALL", 0, 0, 0 },
139 { "FK_390_12", 4, 12, 0 },
140 { "FK_390_20", 4, 20, 0 }
141 };
142
143 // Fixup kinds from .reloc directive are like R_390_NONE. They
144 // do not require any extra processing.
145 if (Kind >= FirstLiteralRelocationKind)
146 return MCAsmBackend::getFixupKindInfo(FK_NONE);
147
148 if (Kind < FirstTargetFixupKind)
149 return MCAsmBackend::getFixupKindInfo(Kind);
150
151 assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
152 "Invalid kind!");
153 return Infos[Kind - FirstTargetFixupKind];
154 }
155
shouldForceRelocation(const MCAssembler &,const MCFixup & Fixup,const MCValue &)156 bool SystemZMCAsmBackend::shouldForceRelocation(const MCAssembler &,
157 const MCFixup &Fixup,
158 const MCValue &) {
159 return Fixup.getKind() >= FirstLiteralRelocationKind;
160 }
161
applyFixup(const MCAssembler & Asm,const MCFixup & Fixup,const MCValue & Target,MutableArrayRef<char> Data,uint64_t Value,bool IsResolved,const MCSubtargetInfo * STI) const162 void SystemZMCAsmBackend::applyFixup(const MCAssembler &Asm,
163 const MCFixup &Fixup,
164 const MCValue &Target,
165 MutableArrayRef<char> Data, uint64_t Value,
166 bool IsResolved,
167 const MCSubtargetInfo *STI) const {
168 MCFixupKind Kind = Fixup.getKind();
169 if (Kind >= FirstLiteralRelocationKind)
170 return;
171 unsigned Offset = Fixup.getOffset();
172 unsigned BitSize = getFixupKindInfo(Kind).TargetSize;
173 unsigned Size = (BitSize + 7) / 8;
174
175 assert(Offset + Size <= Data.size() && "Invalid fixup offset!");
176
177 // Big-endian insertion of Size bytes.
178 Value = extractBitsForFixup(Kind, Value, Fixup, Asm.getContext());
179 if (BitSize < 64)
180 Value &= ((uint64_t)1 << BitSize) - 1;
181 unsigned ShiftValue = (Size * 8) - 8;
182 for (unsigned I = 0; I != Size; ++I) {
183 Data[Offset + I] |= uint8_t(Value >> ShiftValue);
184 ShiftValue -= 8;
185 }
186 }
187
writeNopData(raw_ostream & OS,uint64_t Count,const MCSubtargetInfo * STI) const188 bool SystemZMCAsmBackend::writeNopData(raw_ostream &OS, uint64_t Count,
189 const MCSubtargetInfo *STI) const {
190 for (uint64_t I = 0; I != Count; ++I)
191 OS << '\x7';
192 return true;
193 }
194
createSystemZMCAsmBackend(const Target & T,const MCSubtargetInfo & STI,const MCRegisterInfo & MRI,const MCTargetOptions & Options)195 MCAsmBackend *llvm::createSystemZMCAsmBackend(const Target &T,
196 const MCSubtargetInfo &STI,
197 const MCRegisterInfo &MRI,
198 const MCTargetOptions &Options) {
199 uint8_t OSABI =
200 MCELFObjectTargetWriter::getOSABI(STI.getTargetTriple().getOS());
201 return new SystemZMCAsmBackend(OSABI);
202 }
203