1//===- lib/MC/MCWasmStreamer.cpp - Wasm Object Output ---------------------===//
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// This file assembles .s files and emits Wasm .o object files.
10//
11//===----------------------------------------------------------------------===//
12
13#include "llvm/MC/MCWasmStreamer.h"
14#include "llvm/ADT/SmallString.h"
15#include "llvm/ADT/SmallVector.h"
16#include "llvm/MC/MCAsmBackend.h"
17#include "llvm/MC/MCAssembler.h"
18#include "llvm/MC/MCCodeEmitter.h"
19#include "llvm/MC/MCExpr.h"
20#include "llvm/MC/MCFixup.h"
21#include "llvm/MC/MCFragment.h"
22#include "llvm/MC/MCObjectStreamer.h"
23#include "llvm/MC/MCSection.h"
24#include "llvm/MC/MCSectionWasm.h"
25#include "llvm/MC/MCSymbol.h"
26#include "llvm/MC/MCSymbolWasm.h"
27#include "llvm/MC/TargetRegistry.h"
28#include "llvm/Support/Casting.h"
29#include "llvm/Support/ErrorHandling.h"
30#include "llvm/Support/raw_ostream.h"
31
32namespace llvm {
33class MCContext;
34class MCStreamer;
35class MCSubtargetInfo;
36} // namespace llvm
37
38using namespace llvm;
39
40MCWasmStreamer::~MCWasmStreamer() = default; // anchor.
41
42void MCWasmStreamer::mergeFragment(MCDataFragment *DF, MCDataFragment *EF) {
43 flushPendingLabels(F: DF, FOffset: DF->getContents().size());
44
45 for (unsigned I = 0, E = EF->getFixups().size(); I != E; ++I) {
46 EF->getFixups()[I].setOffset(EF->getFixups()[I].getOffset() +
47 DF->getContents().size());
48 DF->getFixups().push_back(Elt: EF->getFixups()[I]);
49 }
50 if (DF->getSubtargetInfo() == nullptr && EF->getSubtargetInfo())
51 DF->setHasInstructions(*EF->getSubtargetInfo());
52 DF->getContents().append(in_start: EF->getContents().begin(), in_end: EF->getContents().end());
53}
54
55void MCWasmStreamer::emitLabel(MCSymbol *S, SMLoc Loc) {
56 auto *Symbol = cast<MCSymbolWasm>(Val: S);
57 MCObjectStreamer::emitLabel(Symbol, Loc);
58
59 const MCSectionWasm &Section =
60 static_cast<const MCSectionWasm &>(*getCurrentSectionOnly());
61 if (Section.getSegmentFlags() & wasm::WASM_SEG_FLAG_TLS)
62 Symbol->setTLS();
63}
64
65void MCWasmStreamer::emitLabelAtPos(MCSymbol *S, SMLoc Loc, MCFragment *F,
66 uint64_t Offset) {
67 auto *Symbol = cast<MCSymbolWasm>(Val: S);
68 MCObjectStreamer::emitLabelAtPos(Symbol, Loc, F, Offset);
69
70 const MCSectionWasm &Section =
71 static_cast<const MCSectionWasm &>(*getCurrentSectionOnly());
72 if (Section.getSegmentFlags() & wasm::WASM_SEG_FLAG_TLS)
73 Symbol->setTLS();
74}
75
76void MCWasmStreamer::emitAssemblerFlag(MCAssemblerFlag Flag) {
77 // Let the target do whatever target specific stuff it needs to do.
78 getAssembler().getBackend().handleAssemblerFlag(Flag);
79
80 // Do any generic stuff we need to do.
81 llvm_unreachable("invalid assembler flag!");
82}
83
84void MCWasmStreamer::changeSection(MCSection *Section,
85 const MCExpr *Subsection) {
86 MCAssembler &Asm = getAssembler();
87 auto *SectionWasm = cast<MCSectionWasm>(Val: Section);
88 const MCSymbol *Grp = SectionWasm->getGroup();
89 if (Grp)
90 Asm.registerSymbol(Symbol: *Grp);
91
92 this->MCObjectStreamer::changeSection(Section, Subsection);
93 Asm.registerSymbol(Symbol: *Section->getBeginSymbol());
94}
95
96void MCWasmStreamer::emitWeakReference(MCSymbol *Alias,
97 const MCSymbol *Symbol) {
98 getAssembler().registerSymbol(Symbol: *Symbol);
99 const MCExpr *Value = MCSymbolRefExpr::create(
100 Symbol, Kind: MCSymbolRefExpr::VK_WEAKREF, Ctx&: getContext());
101 Alias->setVariableValue(Value);
102}
103
104bool MCWasmStreamer::emitSymbolAttribute(MCSymbol *S, MCSymbolAttr Attribute) {
105 assert(Attribute != MCSA_IndirectSymbol && "indirect symbols not supported");
106
107 auto *Symbol = cast<MCSymbolWasm>(Val: S);
108
109 // Adding a symbol attribute always introduces the symbol; note that an
110 // important side effect of calling registerSymbol here is to register the
111 // symbol with the assembler.
112 getAssembler().registerSymbol(Symbol: *Symbol);
113
114 switch (Attribute) {
115 case MCSA_LazyReference:
116 case MCSA_Reference:
117 case MCSA_SymbolResolver:
118 case MCSA_PrivateExtern:
119 case MCSA_WeakDefinition:
120 case MCSA_WeakDefAutoPrivate:
121 case MCSA_Invalid:
122 case MCSA_IndirectSymbol:
123 case MCSA_Protected:
124 case MCSA_Exported:
125 return false;
126
127 case MCSA_Hidden:
128 Symbol->setHidden(true);
129 break;
130
131 case MCSA_Weak:
132 case MCSA_WeakReference:
133 Symbol->setWeak(true);
134 Symbol->setExternal(true);
135 break;
136
137 case MCSA_Global:
138 Symbol->setExternal(true);
139 break;
140
141 case MCSA_ELF_TypeFunction:
142 Symbol->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
143 break;
144
145 case MCSA_ELF_TypeTLS:
146 Symbol->setTLS();
147 break;
148
149 case MCSA_ELF_TypeObject:
150 case MCSA_Cold:
151 break;
152
153 case MCSA_NoDeadStrip:
154 Symbol->setNoStrip();
155 break;
156
157 default:
158 // unrecognized directive
159 llvm_unreachable("unexpected MCSymbolAttr");
160 return false;
161 }
162
163 return true;
164}
165
166void MCWasmStreamer::emitCommonSymbol(MCSymbol *S, uint64_t Size,
167 Align ByteAlignment) {
168 llvm_unreachable("Common symbols are not yet implemented for Wasm");
169}
170
171void MCWasmStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
172 cast<MCSymbolWasm>(Val: Symbol)->setSize(Value);
173}
174
175void MCWasmStreamer::emitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
176 Align ByteAlignment) {
177 llvm_unreachable("Local common symbols are not yet implemented for Wasm");
178}
179
180void MCWasmStreamer::emitIdent(StringRef IdentString) {
181 // TODO(sbc): Add the ident section once we support mergable strings
182 // sections in the object format
183}
184
185void MCWasmStreamer::emitInstToFragment(const MCInst &Inst,
186 const MCSubtargetInfo &STI) {
187 this->MCObjectStreamer::emitInstToFragment(Inst, STI);
188 MCRelaxableFragment &F = *cast<MCRelaxableFragment>(Val: getCurrentFragment());
189
190 for (auto &Fixup : F.getFixups())
191 fixSymbolsInTLSFixups(expr: Fixup.getValue());
192}
193
194void MCWasmStreamer::emitInstToData(const MCInst &Inst,
195 const MCSubtargetInfo &STI) {
196 MCAssembler &Assembler = getAssembler();
197 SmallVector<MCFixup, 4> Fixups;
198 SmallString<256> Code;
199 Assembler.getEmitter().encodeInstruction(Inst, CB&: Code, Fixups, STI);
200
201 for (auto &Fixup : Fixups)
202 fixSymbolsInTLSFixups(expr: Fixup.getValue());
203
204 // Append the encoded instruction to the current data fragment (or create a
205 // new such fragment if the current fragment is not a data fragment).
206 MCDataFragment *DF = getOrCreateDataFragment();
207
208 // Add the fixups and data.
209 for (unsigned I = 0, E = Fixups.size(); I != E; ++I) {
210 Fixups[I].setOffset(Fixups[I].getOffset() + DF->getContents().size());
211 DF->getFixups().push_back(Elt: Fixups[I]);
212 }
213 DF->setHasInstructions(STI);
214 DF->getContents().append(in_start: Code.begin(), in_end: Code.end());
215}
216
217void MCWasmStreamer::finishImpl() {
218 emitFrames(MAB: nullptr);
219
220 this->MCObjectStreamer::finishImpl();
221}
222
223void MCWasmStreamer::fixSymbolsInTLSFixups(const MCExpr *expr) {
224 switch (expr->getKind()) {
225 case MCExpr::Target:
226 case MCExpr::Constant:
227 break;
228
229 case MCExpr::Binary: {
230 const MCBinaryExpr *be = cast<MCBinaryExpr>(Val: expr);
231 fixSymbolsInTLSFixups(expr: be->getLHS());
232 fixSymbolsInTLSFixups(expr: be->getRHS());
233 break;
234 }
235
236 case MCExpr::SymbolRef: {
237 const MCSymbolRefExpr &symRef = *cast<MCSymbolRefExpr>(Val: expr);
238 switch (symRef.getKind()) {
239 case MCSymbolRefExpr::VK_WASM_TLSREL:
240 case MCSymbolRefExpr::VK_WASM_GOT_TLS:
241 getAssembler().registerSymbol(Symbol: symRef.getSymbol());
242 cast<MCSymbolWasm>(Val: symRef.getSymbol()).setTLS();
243 break;
244 default:
245 break;
246 }
247 break;
248 }
249
250 case MCExpr::Unary:
251 fixSymbolsInTLSFixups(expr: cast<MCUnaryExpr>(Val: expr)->getSubExpr());
252 break;
253 }
254}
255
256void MCWasmStreamer::emitThumbFunc(MCSymbol *Func) {
257 llvm_unreachable("Generic Wasm doesn't support this directive");
258}
259
260void MCWasmStreamer::emitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
261 llvm_unreachable("Wasm doesn't support this directive");
262}
263
264void MCWasmStreamer::emitZerofill(MCSection *Section, MCSymbol *Symbol,
265 uint64_t Size, Align ByteAlignment,
266 SMLoc Loc) {
267 llvm_unreachable("Wasm doesn't support this directive");
268}
269
270void MCWasmStreamer::emitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
271 uint64_t Size, Align ByteAlignment) {
272 llvm_unreachable("Wasm doesn't support this directive");
273}
274
275MCStreamer *llvm::createWasmStreamer(MCContext &Context,
276 std::unique_ptr<MCAsmBackend> &&MAB,
277 std::unique_ptr<MCObjectWriter> &&OW,
278 std::unique_ptr<MCCodeEmitter> &&CE,
279 bool RelaxAll) {
280 MCWasmStreamer *S =
281 new MCWasmStreamer(Context, std::move(MAB), std::move(OW), std::move(CE));
282 if (RelaxAll)
283 S->getAssembler().setRelaxAll(true);
284 return S;
285}
286

source code of llvm/lib/MC/MCWasmStreamer.cpp