forked from OSchip/llvm-project
1390 lines
48 KiB
C++
1390 lines
48 KiB
C++
//===- lib/MC/WasmObjectWriter.cpp - Wasm File Writer ---------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements Wasm object file writer information.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/BinaryFormat/Wasm.h"
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#include "llvm/MC/MCAsmBackend.h"
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#include "llvm/MC/MCAsmLayout.h"
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#include "llvm/MC/MCAssembler.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCFixupKindInfo.h"
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#include "llvm/MC/MCObjectWriter.h"
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#include "llvm/MC/MCSectionWasm.h"
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#include "llvm/MC/MCSymbolWasm.h"
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#include "llvm/MC/MCValue.h"
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#include "llvm/MC/MCWasmObjectWriter.h"
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#include "llvm/Support/Casting.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/LEB128.h"
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#include "llvm/Support/StringSaver.h"
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#include <vector>
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using namespace llvm;
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#define DEBUG_TYPE "mc"
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namespace {
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// Went we ceate the indirect function table we start at 1, so that there is
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// and emtpy slot at 0 and therefore calling a null function pointer will trap.
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static const uint32_t kInitialTableOffset = 1;
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// For patching purposes, we need to remember where each section starts, both
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// for patching up the section size field, and for patching up references to
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// locations within the section.
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struct SectionBookkeeping {
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// Where the size of the section is written.
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uint64_t SizeOffset;
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// Where the contents of the section starts (after the header).
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uint64_t ContentsOffset;
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};
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// The signature of a wasm function, in a struct capable of being used as a
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// DenseMap key.
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struct WasmFunctionType {
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// Support empty and tombstone instances, needed by DenseMap.
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enum { Plain, Empty, Tombstone } State;
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// The return types of the function.
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SmallVector<wasm::ValType, 1> Returns;
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// The parameter types of the function.
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SmallVector<wasm::ValType, 4> Params;
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WasmFunctionType() : State(Plain) {}
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bool operator==(const WasmFunctionType &Other) const {
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return State == Other.State && Returns == Other.Returns &&
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Params == Other.Params;
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}
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};
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// Traits for using WasmFunctionType in a DenseMap.
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struct WasmFunctionTypeDenseMapInfo {
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static WasmFunctionType getEmptyKey() {
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WasmFunctionType FuncTy;
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FuncTy.State = WasmFunctionType::Empty;
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return FuncTy;
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}
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static WasmFunctionType getTombstoneKey() {
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WasmFunctionType FuncTy;
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FuncTy.State = WasmFunctionType::Tombstone;
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return FuncTy;
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}
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static unsigned getHashValue(const WasmFunctionType &FuncTy) {
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uintptr_t Value = FuncTy.State;
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for (wasm::ValType Ret : FuncTy.Returns)
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Value += DenseMapInfo<int32_t>::getHashValue(int32_t(Ret));
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for (wasm::ValType Param : FuncTy.Params)
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Value += DenseMapInfo<int32_t>::getHashValue(int32_t(Param));
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return Value;
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}
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static bool isEqual(const WasmFunctionType &LHS,
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const WasmFunctionType &RHS) {
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return LHS == RHS;
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}
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};
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// A wasm data segment. A wasm binary contains only a single data section
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// but that can contain many segments, each with their own virtual location
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// in memory. Each MCSection data created by llvm is modeled as its own
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// wasm data segment.
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struct WasmDataSegment {
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MCSectionWasm *Section;
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StringRef Name;
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uint32_t Offset;
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uint32_t Alignment;
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uint32_t Flags;
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SmallVector<char, 4> Data;
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};
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// A wasm import to be written into the import section.
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struct WasmImport {
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StringRef ModuleName;
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StringRef FieldName;
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unsigned Kind;
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int32_t Type;
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bool IsMutable;
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};
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// A wasm function to be written into the function section.
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struct WasmFunction {
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int32_t Type;
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const MCSymbolWasm *Sym;
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};
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// A wasm export to be written into the export section.
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struct WasmExport {
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StringRef FieldName;
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unsigned Kind;
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uint32_t Index;
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};
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// A wasm global to be written into the global section.
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struct WasmGlobal {
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wasm::ValType Type;
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bool IsMutable;
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bool HasImport;
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uint64_t InitialValue;
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uint32_t ImportIndex;
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};
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// Information about a single item which is part of a COMDAT. For each data
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// segment or function which is in the COMDAT, there is a corresponding
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// WasmComdatEntry.
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struct WasmComdatEntry {
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unsigned Kind;
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uint32_t Index;
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};
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// Information about a single relocation.
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struct WasmRelocationEntry {
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uint64_t Offset; // Where is the relocation.
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const MCSymbolWasm *Symbol; // The symbol to relocate with.
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int64_t Addend; // A value to add to the symbol.
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unsigned Type; // The type of the relocation.
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const MCSectionWasm *FixupSection;// The section the relocation is targeting.
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WasmRelocationEntry(uint64_t Offset, const MCSymbolWasm *Symbol,
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int64_t Addend, unsigned Type,
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const MCSectionWasm *FixupSection)
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: Offset(Offset), Symbol(Symbol), Addend(Addend), Type(Type),
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FixupSection(FixupSection) {}
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bool hasAddend() const {
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switch (Type) {
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case wasm::R_WEBASSEMBLY_MEMORY_ADDR_LEB:
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case wasm::R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
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case wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32:
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return true;
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default:
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return false;
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}
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}
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void print(raw_ostream &Out) const {
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Out << "Off=" << Offset << ", Sym=" << *Symbol << ", Addend=" << Addend
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<< ", Type=" << Type
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<< ", FixupSection=" << FixupSection->getSectionName();
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}
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#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
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LLVM_DUMP_METHOD void dump() const { print(dbgs()); }
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#endif
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};
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#if !defined(NDEBUG)
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raw_ostream &operator<<(raw_ostream &OS, const WasmRelocationEntry &Rel) {
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Rel.print(OS);
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return OS;
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}
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#endif
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class WasmObjectWriter : public MCObjectWriter {
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/// Helper struct for containing some precomputed information on symbols.
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struct WasmSymbolData {
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const MCSymbolWasm *Symbol;
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StringRef Name;
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// Support lexicographic sorting.
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bool operator<(const WasmSymbolData &RHS) const { return Name < RHS.Name; }
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};
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/// The target specific Wasm writer instance.
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std::unique_ptr<MCWasmObjectTargetWriter> TargetObjectWriter;
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// Relocations for fixing up references in the code section.
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std::vector<WasmRelocationEntry> CodeRelocations;
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// Relocations for fixing up references in the data section.
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std::vector<WasmRelocationEntry> DataRelocations;
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// Index values to use for fixing up call_indirect type indices.
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// Maps function symbols to the index of the type of the function
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DenseMap<const MCSymbolWasm *, uint32_t> TypeIndices;
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// Maps function symbols to the table element index space. Used
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// for TABLE_INDEX relocation types (i.e. address taken functions).
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DenseMap<const MCSymbolWasm *, uint32_t> IndirectSymbolIndices;
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// Maps function/global symbols to the function/global index space.
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DenseMap<const MCSymbolWasm *, uint32_t> SymbolIndices;
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DenseMap<WasmFunctionType, int32_t, WasmFunctionTypeDenseMapInfo>
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FunctionTypeIndices;
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SmallVector<WasmFunctionType, 4> FunctionTypes;
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SmallVector<WasmGlobal, 4> Globals;
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unsigned NumFunctionImports = 0;
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unsigned NumGlobalImports = 0;
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// TargetObjectWriter wrappers.
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bool is64Bit() const { return TargetObjectWriter->is64Bit(); }
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unsigned getRelocType(const MCValue &Target, const MCFixup &Fixup) const {
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return TargetObjectWriter->getRelocType(Target, Fixup);
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}
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void startSection(SectionBookkeeping &Section, unsigned SectionId,
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const char *Name = nullptr);
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void endSection(SectionBookkeeping &Section);
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public:
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WasmObjectWriter(std::unique_ptr<MCWasmObjectTargetWriter> MOTW,
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raw_pwrite_stream &OS)
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: MCObjectWriter(OS, /*IsLittleEndian=*/true),
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TargetObjectWriter(std::move(MOTW)) {}
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~WasmObjectWriter() override;
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private:
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void reset() override {
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CodeRelocations.clear();
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DataRelocations.clear();
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TypeIndices.clear();
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SymbolIndices.clear();
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IndirectSymbolIndices.clear();
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FunctionTypeIndices.clear();
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FunctionTypes.clear();
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Globals.clear();
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MCObjectWriter::reset();
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NumFunctionImports = 0;
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NumGlobalImports = 0;
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}
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void writeHeader(const MCAssembler &Asm);
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void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
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const MCFragment *Fragment, const MCFixup &Fixup,
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MCValue Target, uint64_t &FixedValue) override;
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void executePostLayoutBinding(MCAssembler &Asm,
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const MCAsmLayout &Layout) override;
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void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
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void writeString(const StringRef Str) {
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encodeULEB128(Str.size(), getStream());
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writeBytes(Str);
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}
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void writeValueType(wasm::ValType Ty) {
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encodeSLEB128(int32_t(Ty), getStream());
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}
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void writeTypeSection(ArrayRef<WasmFunctionType> FunctionTypes);
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void writeImportSection(ArrayRef<WasmImport> Imports, uint32_t DataSize,
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uint32_t NumElements);
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void writeFunctionSection(ArrayRef<WasmFunction> Functions);
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void writeGlobalSection();
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void writeExportSection(ArrayRef<WasmExport> Exports);
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void writeElemSection(ArrayRef<uint32_t> TableElems);
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void writeCodeSection(const MCAssembler &Asm, const MCAsmLayout &Layout,
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ArrayRef<WasmFunction> Functions);
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void writeDataSection(ArrayRef<WasmDataSegment> Segments);
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void writeCodeRelocSection();
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void writeDataRelocSection();
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void writeLinkingMetaDataSection(
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ArrayRef<WasmDataSegment> Segments, uint32_t DataSize,
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ArrayRef<std::pair<StringRef, uint32_t>> SymbolFlags,
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ArrayRef<std::pair<uint16_t, uint32_t>> InitFuncs,
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const std::map<StringRef, std::vector<WasmComdatEntry>>& Comdats);
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uint32_t getProvisionalValue(const WasmRelocationEntry &RelEntry);
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void applyRelocations(ArrayRef<WasmRelocationEntry> Relocations,
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uint64_t ContentsOffset);
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void writeRelocations(ArrayRef<WasmRelocationEntry> Relocations);
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uint32_t getRelocationIndexValue(const WasmRelocationEntry &RelEntry);
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uint32_t getFunctionType(const MCSymbolWasm& Symbol);
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uint32_t registerFunctionType(const MCSymbolWasm& Symbol);
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};
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} // end anonymous namespace
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WasmObjectWriter::~WasmObjectWriter() {}
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// Write out a section header and a patchable section size field.
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void WasmObjectWriter::startSection(SectionBookkeeping &Section,
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unsigned SectionId,
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const char *Name) {
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assert((Name != nullptr) == (SectionId == wasm::WASM_SEC_CUSTOM) &&
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"Only custom sections can have names");
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DEBUG(dbgs() << "startSection " << SectionId << ": " << Name << "\n");
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encodeULEB128(SectionId, getStream());
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Section.SizeOffset = getStream().tell();
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// The section size. We don't know the size yet, so reserve enough space
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// for any 32-bit value; we'll patch it later.
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encodeULEB128(UINT32_MAX, getStream());
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// The position where the section starts, for measuring its size.
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Section.ContentsOffset = getStream().tell();
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// Custom sections in wasm also have a string identifier.
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if (SectionId == wasm::WASM_SEC_CUSTOM) {
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assert(Name);
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writeString(StringRef(Name));
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}
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}
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// Now that the section is complete and we know how big it is, patch up the
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// section size field at the start of the section.
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void WasmObjectWriter::endSection(SectionBookkeeping &Section) {
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uint64_t Size = getStream().tell() - Section.ContentsOffset;
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if (uint32_t(Size) != Size)
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report_fatal_error("section size does not fit in a uint32_t");
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DEBUG(dbgs() << "endSection size=" << Size << "\n");
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// Write the final section size to the payload_len field, which follows
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// the section id byte.
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uint8_t Buffer[16];
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unsigned SizeLen = encodeULEB128(Size, Buffer, 5);
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assert(SizeLen == 5);
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getStream().pwrite((char *)Buffer, SizeLen, Section.SizeOffset);
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}
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// Emit the Wasm header.
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void WasmObjectWriter::writeHeader(const MCAssembler &Asm) {
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writeBytes(StringRef(wasm::WasmMagic, sizeof(wasm::WasmMagic)));
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writeLE32(wasm::WasmVersion);
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}
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void WasmObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
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const MCAsmLayout &Layout) {
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}
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void WasmObjectWriter::recordRelocation(MCAssembler &Asm,
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const MCAsmLayout &Layout,
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const MCFragment *Fragment,
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const MCFixup &Fixup, MCValue Target,
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uint64_t &FixedValue) {
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MCAsmBackend &Backend = Asm.getBackend();
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bool IsPCRel = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
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MCFixupKindInfo::FKF_IsPCRel;
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const auto &FixupSection = cast<MCSectionWasm>(*Fragment->getParent());
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uint64_t C = Target.getConstant();
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uint64_t FixupOffset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
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MCContext &Ctx = Asm.getContext();
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// The .init_array isn't translated as data, so don't do relocations in it.
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if (FixupSection.getSectionName().startswith(".init_array"))
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return;
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if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
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assert(RefB->getKind() == MCSymbolRefExpr::VK_None &&
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"Should not have constructed this");
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// Let A, B and C being the components of Target and R be the location of
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// the fixup. If the fixup is not pcrel, we want to compute (A - B + C).
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// If it is pcrel, we want to compute (A - B + C - R).
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// In general, Wasm has no relocations for -B. It can only represent (A + C)
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// or (A + C - R). If B = R + K and the relocation is not pcrel, we can
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// replace B to implement it: (A - R - K + C)
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if (IsPCRel) {
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Ctx.reportError(
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Fixup.getLoc(),
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"No relocation available to represent this relative expression");
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return;
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}
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const auto &SymB = cast<MCSymbolWasm>(RefB->getSymbol());
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if (SymB.isUndefined()) {
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Ctx.reportError(Fixup.getLoc(),
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Twine("symbol '") + SymB.getName() +
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"' can not be undefined in a subtraction expression");
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return;
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}
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assert(!SymB.isAbsolute() && "Should have been folded");
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const MCSection &SecB = SymB.getSection();
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if (&SecB != &FixupSection) {
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Ctx.reportError(Fixup.getLoc(),
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"Cannot represent a difference across sections");
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return;
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}
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uint64_t SymBOffset = Layout.getSymbolOffset(SymB);
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uint64_t K = SymBOffset - FixupOffset;
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IsPCRel = true;
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C -= K;
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}
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// We either rejected the fixup or folded B into C at this point.
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const MCSymbolRefExpr *RefA = Target.getSymA();
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const auto *SymA = RefA ? cast<MCSymbolWasm>(&RefA->getSymbol()) : nullptr;
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if (SymA && SymA->isVariable()) {
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const MCExpr *Expr = SymA->getVariableValue();
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const auto *Inner = cast<MCSymbolRefExpr>(Expr);
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if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF)
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llvm_unreachable("weakref used in reloc not yet implemented");
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}
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// Put any constant offset in an addend. Offsets can be negative, and
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// LLVM expects wrapping, in contrast to wasm's immediates which can't
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// be negative and don't wrap.
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FixedValue = 0;
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if (SymA)
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SymA->setUsedInReloc();
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assert(!IsPCRel);
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assert(SymA);
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unsigned Type = getRelocType(Target, Fixup);
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WasmRelocationEntry Rec(FixupOffset, SymA, C, Type, &FixupSection);
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DEBUG(dbgs() << "WasmReloc: " << Rec << "\n");
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if (FixupSection.isWasmData())
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DataRelocations.push_back(Rec);
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else if (FixupSection.getKind().isText())
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CodeRelocations.push_back(Rec);
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else if (!FixupSection.getKind().isMetadata())
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// TODO(sbc): Add support for debug sections.
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llvm_unreachable("unexpected section type");
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}
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// Write X as an (unsigned) LEB value at offset Offset in Stream, padded
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// to allow patching.
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static void
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WritePatchableLEB(raw_pwrite_stream &Stream, uint32_t X, uint64_t Offset) {
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uint8_t Buffer[5];
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unsigned SizeLen = encodeULEB128(X, Buffer, 5);
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assert(SizeLen == 5);
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Stream.pwrite((char *)Buffer, SizeLen, Offset);
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}
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// Write X as an signed LEB value at offset Offset in Stream, padded
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// to allow patching.
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static void
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WritePatchableSLEB(raw_pwrite_stream &Stream, int32_t X, uint64_t Offset) {
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uint8_t Buffer[5];
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unsigned SizeLen = encodeSLEB128(X, Buffer, 5);
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assert(SizeLen == 5);
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Stream.pwrite((char *)Buffer, SizeLen, Offset);
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}
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// Write X as a plain integer value at offset Offset in Stream.
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static void WriteI32(raw_pwrite_stream &Stream, uint32_t X, uint64_t Offset) {
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uint8_t Buffer[4];
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support::endian::write32le(Buffer, X);
|
|
Stream.pwrite((char *)Buffer, sizeof(Buffer), Offset);
|
|
}
|
|
|
|
static const MCSymbolWasm* ResolveSymbol(const MCSymbolWasm& Symbol) {
|
|
if (Symbol.isVariable()) {
|
|
const MCExpr *Expr = Symbol.getVariableValue();
|
|
auto *Inner = cast<MCSymbolRefExpr>(Expr);
|
|
return cast<MCSymbolWasm>(&Inner->getSymbol());
|
|
}
|
|
return &Symbol;
|
|
}
|
|
|
|
// Compute a value to write into the code at the location covered
|
|
// by RelEntry. This value isn't used by the static linker; it just serves
|
|
// to make the object format more readable and more likely to be directly
|
|
// useable.
|
|
uint32_t
|
|
WasmObjectWriter::getProvisionalValue(const WasmRelocationEntry &RelEntry) {
|
|
|
|
switch (RelEntry.Type) {
|
|
case wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB:
|
|
case wasm::R_WEBASSEMBLY_TABLE_INDEX_I32:
|
|
// Provitional value is the indirect symbol index
|
|
if (!IndirectSymbolIndices.count(RelEntry.Symbol))
|
|
report_fatal_error("symbol not found in table index space: " +
|
|
RelEntry.Symbol->getName());
|
|
return IndirectSymbolIndices[RelEntry.Symbol];
|
|
case wasm::R_WEBASSEMBLY_FUNCTION_INDEX_LEB:
|
|
case wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB:
|
|
case wasm::R_WEBASSEMBLY_GLOBAL_INDEX_LEB:
|
|
// Provitional value is function/type/global index itself
|
|
return getRelocationIndexValue(RelEntry);
|
|
case wasm::R_WEBASSEMBLY_MEMORY_ADDR_LEB:
|
|
case wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32:
|
|
case wasm::R_WEBASSEMBLY_MEMORY_ADDR_SLEB: {
|
|
// Provitional value is address of the global
|
|
const MCSymbolWasm *Sym = ResolveSymbol(*RelEntry.Symbol);
|
|
// For undefined symbols, use zero
|
|
if (!Sym->isDefined())
|
|
return 0;
|
|
|
|
uint32_t GlobalIndex = SymbolIndices[Sym];
|
|
const WasmGlobal& Global = Globals[GlobalIndex - NumGlobalImports];
|
|
uint64_t Address = Global.InitialValue + RelEntry.Addend;
|
|
|
|
// Ignore overflow. LLVM allows address arithmetic to silently wrap.
|
|
return Address;
|
|
}
|
|
default:
|
|
llvm_unreachable("invalid relocation type");
|
|
}
|
|
}
|
|
|
|
static void addData(SmallVectorImpl<char> &DataBytes,
|
|
MCSectionWasm &DataSection) {
|
|
DEBUG(errs() << "addData: " << DataSection.getSectionName() << "\n");
|
|
|
|
DataBytes.resize(alignTo(DataBytes.size(), DataSection.getAlignment()));
|
|
|
|
size_t LastFragmentSize = 0;
|
|
for (const MCFragment &Frag : DataSection) {
|
|
if (Frag.hasInstructions())
|
|
report_fatal_error("only data supported in data sections");
|
|
|
|
if (auto *Align = dyn_cast<MCAlignFragment>(&Frag)) {
|
|
if (Align->getValueSize() != 1)
|
|
report_fatal_error("only byte values supported for alignment");
|
|
// If nops are requested, use zeros, as this is the data section.
|
|
uint8_t Value = Align->hasEmitNops() ? 0 : Align->getValue();
|
|
uint64_t Size = std::min<uint64_t>(alignTo(DataBytes.size(),
|
|
Align->getAlignment()),
|
|
DataBytes.size() +
|
|
Align->getMaxBytesToEmit());
|
|
DataBytes.resize(Size, Value);
|
|
} else if (auto *Fill = dyn_cast<MCFillFragment>(&Frag)) {
|
|
int64_t Size;
|
|
if (!Fill->getSize().evaluateAsAbsolute(Size))
|
|
llvm_unreachable("The fill should be an assembler constant");
|
|
DataBytes.insert(DataBytes.end(), Size, Fill->getValue());
|
|
} else {
|
|
const auto &DataFrag = cast<MCDataFragment>(Frag);
|
|
const SmallVectorImpl<char> &Contents = DataFrag.getContents();
|
|
|
|
DataBytes.insert(DataBytes.end(), Contents.begin(), Contents.end());
|
|
LastFragmentSize = Contents.size();
|
|
}
|
|
}
|
|
|
|
// Don't allow empty segments, or segments that end with zero-sized
|
|
// fragment, otherwise the linker cannot map symbols to a unique
|
|
// data segment. This can be triggered by zero-sized structs
|
|
// See: test/MC/WebAssembly/bss.ll
|
|
if (LastFragmentSize == 0)
|
|
DataBytes.resize(DataBytes.size() + 1);
|
|
DEBUG(dbgs() << "addData -> " << DataBytes.size() << "\n");
|
|
}
|
|
|
|
uint32_t
|
|
WasmObjectWriter::getRelocationIndexValue(const WasmRelocationEntry &RelEntry) {
|
|
if (RelEntry.Type == wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB) {
|
|
if (!TypeIndices.count(RelEntry.Symbol))
|
|
report_fatal_error("symbol not found in type index space: " +
|
|
RelEntry.Symbol->getName());
|
|
return TypeIndices[RelEntry.Symbol];
|
|
}
|
|
|
|
if (!SymbolIndices.count(RelEntry.Symbol))
|
|
report_fatal_error("symbol not found in function/global index space: " +
|
|
RelEntry.Symbol->getName());
|
|
return SymbolIndices[RelEntry.Symbol];
|
|
}
|
|
|
|
// Apply the portions of the relocation records that we can handle ourselves
|
|
// directly.
|
|
void WasmObjectWriter::applyRelocations(
|
|
ArrayRef<WasmRelocationEntry> Relocations, uint64_t ContentsOffset) {
|
|
raw_pwrite_stream &Stream = getStream();
|
|
for (const WasmRelocationEntry &RelEntry : Relocations) {
|
|
uint64_t Offset = ContentsOffset +
|
|
RelEntry.FixupSection->getSectionOffset() +
|
|
RelEntry.Offset;
|
|
|
|
DEBUG(dbgs() << "applyRelocation: " << RelEntry << "\n");
|
|
uint32_t Value = getProvisionalValue(RelEntry);
|
|
|
|
switch (RelEntry.Type) {
|
|
case wasm::R_WEBASSEMBLY_FUNCTION_INDEX_LEB:
|
|
case wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB:
|
|
case wasm::R_WEBASSEMBLY_GLOBAL_INDEX_LEB:
|
|
case wasm::R_WEBASSEMBLY_MEMORY_ADDR_LEB:
|
|
WritePatchableLEB(Stream, Value, Offset);
|
|
break;
|
|
case wasm::R_WEBASSEMBLY_TABLE_INDEX_I32:
|
|
case wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32:
|
|
WriteI32(Stream, Value, Offset);
|
|
break;
|
|
case wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB:
|
|
case wasm::R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
|
|
WritePatchableSLEB(Stream, Value, Offset);
|
|
break;
|
|
default:
|
|
llvm_unreachable("invalid relocation type");
|
|
}
|
|
}
|
|
}
|
|
|
|
// Write out the portions of the relocation records that the linker will
|
|
// need to handle.
|
|
void WasmObjectWriter::writeRelocations(
|
|
ArrayRef<WasmRelocationEntry> Relocations) {
|
|
raw_pwrite_stream &Stream = getStream();
|
|
for (const WasmRelocationEntry& RelEntry : Relocations) {
|
|
|
|
uint64_t Offset = RelEntry.Offset +
|
|
RelEntry.FixupSection->getSectionOffset();
|
|
uint32_t Index = getRelocationIndexValue(RelEntry);
|
|
|
|
encodeULEB128(RelEntry.Type, Stream);
|
|
encodeULEB128(Offset, Stream);
|
|
encodeULEB128(Index, Stream);
|
|
if (RelEntry.hasAddend())
|
|
encodeSLEB128(RelEntry.Addend, Stream);
|
|
}
|
|
}
|
|
|
|
void WasmObjectWriter::writeTypeSection(
|
|
ArrayRef<WasmFunctionType> FunctionTypes) {
|
|
if (FunctionTypes.empty())
|
|
return;
|
|
|
|
SectionBookkeeping Section;
|
|
startSection(Section, wasm::WASM_SEC_TYPE);
|
|
|
|
encodeULEB128(FunctionTypes.size(), getStream());
|
|
|
|
for (const WasmFunctionType &FuncTy : FunctionTypes) {
|
|
encodeSLEB128(wasm::WASM_TYPE_FUNC, getStream());
|
|
encodeULEB128(FuncTy.Params.size(), getStream());
|
|
for (wasm::ValType Ty : FuncTy.Params)
|
|
writeValueType(Ty);
|
|
encodeULEB128(FuncTy.Returns.size(), getStream());
|
|
for (wasm::ValType Ty : FuncTy.Returns)
|
|
writeValueType(Ty);
|
|
}
|
|
|
|
endSection(Section);
|
|
}
|
|
|
|
void WasmObjectWriter::writeImportSection(ArrayRef<WasmImport> Imports,
|
|
uint32_t DataSize,
|
|
uint32_t NumElements) {
|
|
if (Imports.empty())
|
|
return;
|
|
|
|
uint32_t NumPages = (DataSize + wasm::WasmPageSize - 1) / wasm::WasmPageSize;
|
|
|
|
SectionBookkeeping Section;
|
|
startSection(Section, wasm::WASM_SEC_IMPORT);
|
|
|
|
encodeULEB128(Imports.size(), getStream());
|
|
for (const WasmImport &Import : Imports) {
|
|
writeString(Import.ModuleName);
|
|
writeString(Import.FieldName);
|
|
|
|
encodeULEB128(Import.Kind, getStream());
|
|
|
|
switch (Import.Kind) {
|
|
case wasm::WASM_EXTERNAL_FUNCTION:
|
|
encodeULEB128(Import.Type, getStream());
|
|
break;
|
|
case wasm::WASM_EXTERNAL_GLOBAL:
|
|
encodeSLEB128(int32_t(Import.Type), getStream());
|
|
encodeULEB128(int32_t(Import.IsMutable), getStream());
|
|
break;
|
|
case wasm::WASM_EXTERNAL_MEMORY:
|
|
encodeULEB128(0, getStream()); // flags
|
|
encodeULEB128(NumPages, getStream()); // initial
|
|
break;
|
|
case wasm::WASM_EXTERNAL_TABLE:
|
|
encodeSLEB128(int32_t(Import.Type), getStream());
|
|
encodeULEB128(0, getStream()); // flags
|
|
encodeULEB128(NumElements, getStream()); // initial
|
|
break;
|
|
default:
|
|
llvm_unreachable("unsupported import kind");
|
|
}
|
|
}
|
|
|
|
endSection(Section);
|
|
}
|
|
|
|
void WasmObjectWriter::writeFunctionSection(ArrayRef<WasmFunction> Functions) {
|
|
if (Functions.empty())
|
|
return;
|
|
|
|
SectionBookkeeping Section;
|
|
startSection(Section, wasm::WASM_SEC_FUNCTION);
|
|
|
|
encodeULEB128(Functions.size(), getStream());
|
|
for (const WasmFunction &Func : Functions)
|
|
encodeULEB128(Func.Type, getStream());
|
|
|
|
endSection(Section);
|
|
}
|
|
|
|
void WasmObjectWriter::writeGlobalSection() {
|
|
if (Globals.empty())
|
|
return;
|
|
|
|
SectionBookkeeping Section;
|
|
startSection(Section, wasm::WASM_SEC_GLOBAL);
|
|
|
|
encodeULEB128(Globals.size(), getStream());
|
|
for (const WasmGlobal &Global : Globals) {
|
|
writeValueType(Global.Type);
|
|
write8(Global.IsMutable);
|
|
|
|
if (Global.HasImport) {
|
|
assert(Global.InitialValue == 0);
|
|
write8(wasm::WASM_OPCODE_GET_GLOBAL);
|
|
encodeULEB128(Global.ImportIndex, getStream());
|
|
} else {
|
|
assert(Global.ImportIndex == 0);
|
|
write8(wasm::WASM_OPCODE_I32_CONST);
|
|
encodeSLEB128(Global.InitialValue, getStream()); // offset
|
|
}
|
|
write8(wasm::WASM_OPCODE_END);
|
|
}
|
|
|
|
endSection(Section);
|
|
}
|
|
|
|
void WasmObjectWriter::writeExportSection(ArrayRef<WasmExport> Exports) {
|
|
if (Exports.empty())
|
|
return;
|
|
|
|
SectionBookkeeping Section;
|
|
startSection(Section, wasm::WASM_SEC_EXPORT);
|
|
|
|
encodeULEB128(Exports.size(), getStream());
|
|
for (const WasmExport &Export : Exports) {
|
|
writeString(Export.FieldName);
|
|
encodeSLEB128(Export.Kind, getStream());
|
|
encodeULEB128(Export.Index, getStream());
|
|
}
|
|
|
|
endSection(Section);
|
|
}
|
|
|
|
void WasmObjectWriter::writeElemSection(ArrayRef<uint32_t> TableElems) {
|
|
if (TableElems.empty())
|
|
return;
|
|
|
|
SectionBookkeeping Section;
|
|
startSection(Section, wasm::WASM_SEC_ELEM);
|
|
|
|
encodeULEB128(1, getStream()); // number of "segments"
|
|
encodeULEB128(0, getStream()); // the table index
|
|
|
|
// init expr for starting offset
|
|
write8(wasm::WASM_OPCODE_I32_CONST);
|
|
encodeSLEB128(kInitialTableOffset, getStream());
|
|
write8(wasm::WASM_OPCODE_END);
|
|
|
|
encodeULEB128(TableElems.size(), getStream());
|
|
for (uint32_t Elem : TableElems)
|
|
encodeULEB128(Elem, getStream());
|
|
|
|
endSection(Section);
|
|
}
|
|
|
|
void WasmObjectWriter::writeCodeSection(const MCAssembler &Asm,
|
|
const MCAsmLayout &Layout,
|
|
ArrayRef<WasmFunction> Functions) {
|
|
if (Functions.empty())
|
|
return;
|
|
|
|
SectionBookkeeping Section;
|
|
startSection(Section, wasm::WASM_SEC_CODE);
|
|
|
|
encodeULEB128(Functions.size(), getStream());
|
|
|
|
for (const WasmFunction &Func : Functions) {
|
|
auto &FuncSection = static_cast<MCSectionWasm &>(Func.Sym->getSection());
|
|
|
|
int64_t Size = 0;
|
|
if (!Func.Sym->getSize()->evaluateAsAbsolute(Size, Layout))
|
|
report_fatal_error(".size expression must be evaluatable");
|
|
|
|
encodeULEB128(Size, getStream());
|
|
FuncSection.setSectionOffset(getStream().tell() - Section.ContentsOffset);
|
|
Asm.writeSectionData(&FuncSection, Layout);
|
|
}
|
|
|
|
// Apply fixups.
|
|
applyRelocations(CodeRelocations, Section.ContentsOffset);
|
|
|
|
endSection(Section);
|
|
}
|
|
|
|
void WasmObjectWriter::writeDataSection(ArrayRef<WasmDataSegment> Segments) {
|
|
if (Segments.empty())
|
|
return;
|
|
|
|
SectionBookkeeping Section;
|
|
startSection(Section, wasm::WASM_SEC_DATA);
|
|
|
|
encodeULEB128(Segments.size(), getStream()); // count
|
|
|
|
for (const WasmDataSegment & Segment : Segments) {
|
|
encodeULEB128(0, getStream()); // memory index
|
|
write8(wasm::WASM_OPCODE_I32_CONST);
|
|
encodeSLEB128(Segment.Offset, getStream()); // offset
|
|
write8(wasm::WASM_OPCODE_END);
|
|
encodeULEB128(Segment.Data.size(), getStream()); // size
|
|
Segment.Section->setSectionOffset(getStream().tell() - Section.ContentsOffset);
|
|
writeBytes(Segment.Data); // data
|
|
}
|
|
|
|
// Apply fixups.
|
|
applyRelocations(DataRelocations, Section.ContentsOffset);
|
|
|
|
endSection(Section);
|
|
}
|
|
|
|
void WasmObjectWriter::writeCodeRelocSection() {
|
|
// See: https://github.com/WebAssembly/tool-conventions/blob/master/Linking.md
|
|
// for descriptions of the reloc sections.
|
|
|
|
if (CodeRelocations.empty())
|
|
return;
|
|
|
|
SectionBookkeeping Section;
|
|
startSection(Section, wasm::WASM_SEC_CUSTOM, "reloc.CODE");
|
|
|
|
encodeULEB128(wasm::WASM_SEC_CODE, getStream());
|
|
encodeULEB128(CodeRelocations.size(), getStream());
|
|
|
|
writeRelocations(CodeRelocations);
|
|
|
|
endSection(Section);
|
|
}
|
|
|
|
void WasmObjectWriter::writeDataRelocSection() {
|
|
// See: https://github.com/WebAssembly/tool-conventions/blob/master/Linking.md
|
|
// for descriptions of the reloc sections.
|
|
|
|
if (DataRelocations.empty())
|
|
return;
|
|
|
|
SectionBookkeeping Section;
|
|
startSection(Section, wasm::WASM_SEC_CUSTOM, "reloc.DATA");
|
|
|
|
encodeULEB128(wasm::WASM_SEC_DATA, getStream());
|
|
encodeULEB128(DataRelocations.size(), getStream());
|
|
|
|
writeRelocations(DataRelocations);
|
|
|
|
endSection(Section);
|
|
}
|
|
|
|
void WasmObjectWriter::writeLinkingMetaDataSection(
|
|
ArrayRef<WasmDataSegment> Segments, uint32_t DataSize,
|
|
ArrayRef<std::pair<StringRef, uint32_t>> SymbolFlags,
|
|
ArrayRef<std::pair<uint16_t, uint32_t>> InitFuncs,
|
|
const std::map<StringRef, std::vector<WasmComdatEntry>>& Comdats) {
|
|
SectionBookkeeping Section;
|
|
startSection(Section, wasm::WASM_SEC_CUSTOM, "linking");
|
|
SectionBookkeeping SubSection;
|
|
|
|
if (SymbolFlags.size() != 0) {
|
|
startSection(SubSection, wasm::WASM_SYMBOL_INFO);
|
|
encodeULEB128(SymbolFlags.size(), getStream());
|
|
for (auto Pair: SymbolFlags) {
|
|
writeString(Pair.first);
|
|
encodeULEB128(Pair.second, getStream());
|
|
}
|
|
endSection(SubSection);
|
|
}
|
|
|
|
if (DataSize > 0) {
|
|
startSection(SubSection, wasm::WASM_DATA_SIZE);
|
|
encodeULEB128(DataSize, getStream());
|
|
endSection(SubSection);
|
|
}
|
|
|
|
if (Segments.size()) {
|
|
startSection(SubSection, wasm::WASM_SEGMENT_INFO);
|
|
encodeULEB128(Segments.size(), getStream());
|
|
for (const WasmDataSegment &Segment : Segments) {
|
|
writeString(Segment.Name);
|
|
encodeULEB128(Segment.Alignment, getStream());
|
|
encodeULEB128(Segment.Flags, getStream());
|
|
}
|
|
endSection(SubSection);
|
|
}
|
|
|
|
if (!InitFuncs.empty()) {
|
|
startSection(SubSection, wasm::WASM_INIT_FUNCS);
|
|
encodeULEB128(InitFuncs.size(), getStream());
|
|
for (auto &StartFunc : InitFuncs) {
|
|
encodeULEB128(StartFunc.first, getStream()); // priority
|
|
encodeULEB128(StartFunc.second, getStream()); // function index
|
|
}
|
|
endSection(SubSection);
|
|
}
|
|
|
|
if (Comdats.size()) {
|
|
startSection(SubSection, wasm::WASM_COMDAT_INFO);
|
|
encodeULEB128(Comdats.size(), getStream());
|
|
for (const auto &C : Comdats) {
|
|
writeString(C.first);
|
|
encodeULEB128(0, getStream()); // flags for future use
|
|
encodeULEB128(C.second.size(), getStream());
|
|
for (const WasmComdatEntry &Entry : C.second) {
|
|
encodeULEB128(Entry.Kind, getStream());
|
|
encodeULEB128(Entry.Index, getStream());
|
|
}
|
|
}
|
|
endSection(SubSection);
|
|
}
|
|
|
|
endSection(Section);
|
|
}
|
|
|
|
uint32_t WasmObjectWriter::getFunctionType(const MCSymbolWasm& Symbol) {
|
|
assert(Symbol.isFunction());
|
|
assert(TypeIndices.count(&Symbol));
|
|
return TypeIndices[&Symbol];
|
|
}
|
|
|
|
uint32_t WasmObjectWriter::registerFunctionType(const MCSymbolWasm& Symbol) {
|
|
assert(Symbol.isFunction());
|
|
|
|
WasmFunctionType F;
|
|
const MCSymbolWasm* ResolvedSym = ResolveSymbol(Symbol);
|
|
F.Returns = ResolvedSym->getReturns();
|
|
F.Params = ResolvedSym->getParams();
|
|
|
|
auto Pair =
|
|
FunctionTypeIndices.insert(std::make_pair(F, FunctionTypes.size()));
|
|
if (Pair.second)
|
|
FunctionTypes.push_back(F);
|
|
TypeIndices[&Symbol] = Pair.first->second;
|
|
|
|
DEBUG(dbgs() << "registerFunctionType: " << Symbol << " new:" << Pair.second << "\n");
|
|
DEBUG(dbgs() << " -> type index: " << Pair.first->second << "\n");
|
|
return Pair.first->second;
|
|
}
|
|
|
|
void WasmObjectWriter::writeObject(MCAssembler &Asm,
|
|
const MCAsmLayout &Layout) {
|
|
DEBUG(dbgs() << "WasmObjectWriter::writeObject\n");
|
|
MCContext &Ctx = Asm.getContext();
|
|
wasm::ValType PtrType = is64Bit() ? wasm::ValType::I64 : wasm::ValType::I32;
|
|
|
|
// Collect information from the available symbols.
|
|
SmallVector<WasmFunction, 4> Functions;
|
|
SmallVector<uint32_t, 4> TableElems;
|
|
SmallVector<WasmImport, 4> Imports;
|
|
SmallVector<WasmExport, 4> Exports;
|
|
SmallVector<std::pair<StringRef, uint32_t>, 4> SymbolFlags;
|
|
SmallVector<std::pair<uint16_t, uint32_t>, 2> InitFuncs;
|
|
std::map<StringRef, std::vector<WasmComdatEntry>> Comdats;
|
|
SmallVector<WasmDataSegment, 4> DataSegments;
|
|
uint32_t DataSize = 0;
|
|
|
|
// In the special .global_variables section, we've encoded global
|
|
// variables used by the function. Translate them into the Globals
|
|
// list.
|
|
MCSectionWasm *GlobalVars =
|
|
Ctx.getWasmSection(".global_variables", SectionKind::getMetadata());
|
|
if (!GlobalVars->getFragmentList().empty()) {
|
|
if (GlobalVars->getFragmentList().size() != 1)
|
|
report_fatal_error("only one .global_variables fragment supported");
|
|
const MCFragment &Frag = *GlobalVars->begin();
|
|
if (Frag.hasInstructions() || Frag.getKind() != MCFragment::FT_Data)
|
|
report_fatal_error("only data supported in .global_variables");
|
|
const auto &DataFrag = cast<MCDataFragment>(Frag);
|
|
if (!DataFrag.getFixups().empty())
|
|
report_fatal_error("fixups not supported in .global_variables");
|
|
const SmallVectorImpl<char> &Contents = DataFrag.getContents();
|
|
for (const uint8_t *p = (const uint8_t *)Contents.data(),
|
|
*end = (const uint8_t *)Contents.data() + Contents.size();
|
|
p != end; ) {
|
|
WasmGlobal G;
|
|
if (end - p < 3)
|
|
report_fatal_error("truncated global variable encoding");
|
|
G.Type = wasm::ValType(int8_t(*p++));
|
|
G.IsMutable = bool(*p++);
|
|
G.HasImport = bool(*p++);
|
|
if (G.HasImport) {
|
|
G.InitialValue = 0;
|
|
|
|
WasmImport Import;
|
|
Import.ModuleName = (const char *)p;
|
|
const uint8_t *nul = (const uint8_t *)memchr(p, '\0', end - p);
|
|
if (!nul)
|
|
report_fatal_error("global module name must be nul-terminated");
|
|
p = nul + 1;
|
|
nul = (const uint8_t *)memchr(p, '\0', end - p);
|
|
if (!nul)
|
|
report_fatal_error("global base name must be nul-terminated");
|
|
Import.FieldName = (const char *)p;
|
|
p = nul + 1;
|
|
|
|
Import.Kind = wasm::WASM_EXTERNAL_GLOBAL;
|
|
Import.Type = int32_t(G.Type);
|
|
|
|
G.ImportIndex = NumGlobalImports;
|
|
++NumGlobalImports;
|
|
|
|
Imports.push_back(Import);
|
|
} else {
|
|
unsigned n;
|
|
G.InitialValue = decodeSLEB128(p, &n);
|
|
G.ImportIndex = 0;
|
|
if ((ptrdiff_t)n > end - p)
|
|
report_fatal_error("global initial value must be valid SLEB128");
|
|
p += n;
|
|
}
|
|
Globals.push_back(G);
|
|
}
|
|
}
|
|
|
|
// For now, always emit the memory import, since loads and stores are not
|
|
// valid without it. In the future, we could perhaps be more clever and omit
|
|
// it if there are no loads or stores.
|
|
MCSymbolWasm *MemorySym =
|
|
cast<MCSymbolWasm>(Ctx.getOrCreateSymbol("__linear_memory"));
|
|
WasmImport MemImport;
|
|
MemImport.ModuleName = MemorySym->getModuleName();
|
|
MemImport.FieldName = MemorySym->getName();
|
|
MemImport.Kind = wasm::WASM_EXTERNAL_MEMORY;
|
|
Imports.push_back(MemImport);
|
|
|
|
// For now, always emit the table section, since indirect calls are not
|
|
// valid without it. In the future, we could perhaps be more clever and omit
|
|
// it if there are no indirect calls.
|
|
MCSymbolWasm *TableSym =
|
|
cast<MCSymbolWasm>(Ctx.getOrCreateSymbol("__indirect_function_table"));
|
|
WasmImport TableImport;
|
|
TableImport.ModuleName = TableSym->getModuleName();
|
|
TableImport.FieldName = TableSym->getName();
|
|
TableImport.Kind = wasm::WASM_EXTERNAL_TABLE;
|
|
TableImport.Type = wasm::WASM_TYPE_ANYFUNC;
|
|
Imports.push_back(TableImport);
|
|
|
|
// Populate FunctionTypeIndices and Imports.
|
|
for (const MCSymbol &S : Asm.symbols()) {
|
|
const auto &WS = static_cast<const MCSymbolWasm &>(S);
|
|
|
|
// Register types for all functions, including those with private linkage
|
|
// (because wasm always needs a type signature).
|
|
if (WS.isFunction())
|
|
registerFunctionType(WS);
|
|
|
|
if (WS.isTemporary())
|
|
continue;
|
|
|
|
// If the symbol is not defined in this translation unit, import it.
|
|
if ((!WS.isDefined() && !WS.isComdat()) ||
|
|
WS.isVariable()) {
|
|
WasmImport Import;
|
|
Import.ModuleName = WS.getModuleName();
|
|
Import.FieldName = WS.getName();
|
|
|
|
if (WS.isFunction()) {
|
|
Import.Kind = wasm::WASM_EXTERNAL_FUNCTION;
|
|
Import.Type = getFunctionType(WS);
|
|
SymbolIndices[&WS] = NumFunctionImports;
|
|
++NumFunctionImports;
|
|
} else {
|
|
Import.Kind = wasm::WASM_EXTERNAL_GLOBAL;
|
|
Import.Type = int32_t(PtrType);
|
|
Import.IsMutable = false;
|
|
SymbolIndices[&WS] = NumGlobalImports;
|
|
|
|
// If this global is the stack pointer, make it mutable.
|
|
if (WS.getName() == "__stack_pointer")
|
|
Import.IsMutable = true;
|
|
|
|
++NumGlobalImports;
|
|
}
|
|
|
|
Imports.push_back(Import);
|
|
}
|
|
}
|
|
|
|
for (MCSection &Sec : Asm) {
|
|
auto &Section = static_cast<MCSectionWasm &>(Sec);
|
|
if (!Section.isWasmData())
|
|
continue;
|
|
|
|
// .init_array sections are handled specially elsewhere.
|
|
if (cast<MCSectionWasm>(Sec).getSectionName().startswith(".init_array"))
|
|
continue;
|
|
|
|
DataSize = alignTo(DataSize, Section.getAlignment());
|
|
DataSegments.emplace_back();
|
|
WasmDataSegment &Segment = DataSegments.back();
|
|
Segment.Name = Section.getSectionName();
|
|
Segment.Offset = DataSize;
|
|
Segment.Section = &Section;
|
|
addData(Segment.Data, Section);
|
|
Segment.Alignment = Section.getAlignment();
|
|
Segment.Flags = 0;
|
|
DataSize += Segment.Data.size();
|
|
Section.setMemoryOffset(Segment.Offset);
|
|
|
|
if (const MCSymbolWasm *C = Section.getGroup()) {
|
|
Comdats[C->getName()].emplace_back(
|
|
WasmComdatEntry{wasm::WASM_COMDAT_DATA,
|
|
static_cast<uint32_t>(DataSegments.size()) - 1});
|
|
}
|
|
}
|
|
|
|
// Handle regular defined and undefined symbols.
|
|
for (const MCSymbol &S : Asm.symbols()) {
|
|
// Ignore unnamed temporary symbols, which aren't ever exported, imported,
|
|
// or used in relocations.
|
|
if (S.isTemporary() && S.getName().empty())
|
|
continue;
|
|
|
|
const auto &WS = static_cast<const MCSymbolWasm &>(S);
|
|
DEBUG(dbgs() << "MCSymbol: '" << S << "'"
|
|
<< " isDefined=" << S.isDefined() << " isExternal="
|
|
<< S.isExternal() << " isTemporary=" << S.isTemporary()
|
|
<< " isFunction=" << WS.isFunction()
|
|
<< " isWeak=" << WS.isWeak()
|
|
<< " isHidden=" << WS.isHidden()
|
|
<< " isVariable=" << WS.isVariable() << "\n");
|
|
|
|
if (WS.isWeak() || WS.isHidden()) {
|
|
uint32_t Flags = (WS.isWeak() ? wasm::WASM_SYMBOL_BINDING_WEAK : 0) |
|
|
(WS.isHidden() ? wasm::WASM_SYMBOL_VISIBILITY_HIDDEN : 0);
|
|
SymbolFlags.emplace_back(WS.getName(), Flags);
|
|
}
|
|
|
|
if (WS.isVariable())
|
|
continue;
|
|
|
|
unsigned Index;
|
|
|
|
if (WS.isFunction()) {
|
|
if (WS.isDefined()) {
|
|
if (WS.getOffset() != 0)
|
|
report_fatal_error(
|
|
"function sections must contain one function each");
|
|
|
|
if (WS.getSize() == 0)
|
|
report_fatal_error(
|
|
"function symbols must have a size set with .size");
|
|
|
|
// A definition. Take the next available index.
|
|
Index = NumFunctionImports + Functions.size();
|
|
|
|
// Prepare the function.
|
|
WasmFunction Func;
|
|
Func.Type = getFunctionType(WS);
|
|
Func.Sym = &WS;
|
|
SymbolIndices[&WS] = Index;
|
|
Functions.push_back(Func);
|
|
} else {
|
|
// An import; the index was assigned above.
|
|
Index = SymbolIndices.find(&WS)->second;
|
|
}
|
|
|
|
DEBUG(dbgs() << " -> function index: " << Index << "\n");
|
|
} else {
|
|
if (WS.isTemporary() && !WS.getSize())
|
|
continue;
|
|
|
|
if (!WS.isDefined())
|
|
continue;
|
|
|
|
if (!WS.getSize())
|
|
report_fatal_error("data symbols must have a size set with .size: " +
|
|
WS.getName());
|
|
|
|
int64_t Size = 0;
|
|
if (!WS.getSize()->evaluateAsAbsolute(Size, Layout))
|
|
report_fatal_error(".size expression must be evaluatable");
|
|
|
|
// For each global, prepare a corresponding wasm global holding its
|
|
// address. For externals these will also be named exports.
|
|
Index = NumGlobalImports + Globals.size();
|
|
auto &DataSection = static_cast<MCSectionWasm &>(WS.getSection());
|
|
assert(DataSection.isWasmData());
|
|
|
|
WasmGlobal Global;
|
|
Global.Type = PtrType;
|
|
Global.IsMutable = false;
|
|
Global.HasImport = false;
|
|
Global.InitialValue = DataSection.getMemoryOffset() + Layout.getSymbolOffset(WS);
|
|
Global.ImportIndex = 0;
|
|
SymbolIndices[&WS] = Index;
|
|
DEBUG(dbgs() << " -> global index: " << Index << "\n");
|
|
Globals.push_back(Global);
|
|
}
|
|
|
|
// If the symbol is visible outside this translation unit, export it.
|
|
if (WS.isDefined()) {
|
|
WasmExport Export;
|
|
Export.FieldName = WS.getName();
|
|
Export.Index = Index;
|
|
if (WS.isFunction())
|
|
Export.Kind = wasm::WASM_EXTERNAL_FUNCTION;
|
|
else
|
|
Export.Kind = wasm::WASM_EXTERNAL_GLOBAL;
|
|
DEBUG(dbgs() << " -> export " << Exports.size() << "\n");
|
|
Exports.push_back(Export);
|
|
|
|
if (!WS.isExternal())
|
|
SymbolFlags.emplace_back(WS.getName(), wasm::WASM_SYMBOL_BINDING_LOCAL);
|
|
|
|
if (WS.isFunction()) {
|
|
auto &Section = static_cast<MCSectionWasm &>(WS.getSection());
|
|
if (const MCSymbolWasm *C = Section.getGroup())
|
|
Comdats[C->getName()].emplace_back(
|
|
WasmComdatEntry{wasm::WASM_COMDAT_FUNCTION, Index});
|
|
}
|
|
}
|
|
}
|
|
|
|
// Handle weak aliases. We need to process these in a separate pass because
|
|
// we need to have processed the target of the alias before the alias itself
|
|
// and the symbols are not necessarily ordered in this way.
|
|
for (const MCSymbol &S : Asm.symbols()) {
|
|
if (!S.isVariable())
|
|
continue;
|
|
|
|
assert(S.isDefined());
|
|
|
|
// Find the target symbol of this weak alias and export that index
|
|
const auto &WS = static_cast<const MCSymbolWasm &>(S);
|
|
const MCSymbolWasm *ResolvedSym = ResolveSymbol(WS);
|
|
DEBUG(dbgs() << WS.getName() << ": weak alias of '" << *ResolvedSym << "'\n");
|
|
assert(SymbolIndices.count(ResolvedSym) > 0);
|
|
uint32_t Index = SymbolIndices.find(ResolvedSym)->second;
|
|
DEBUG(dbgs() << " -> index:" << Index << "\n");
|
|
|
|
WasmExport Export;
|
|
Export.FieldName = WS.getName();
|
|
Export.Index = Index;
|
|
if (WS.isFunction())
|
|
Export.Kind = wasm::WASM_EXTERNAL_FUNCTION;
|
|
else
|
|
Export.Kind = wasm::WASM_EXTERNAL_GLOBAL;
|
|
DEBUG(dbgs() << " -> export " << Exports.size() << "\n");
|
|
Exports.push_back(Export);
|
|
|
|
if (!WS.isExternal())
|
|
SymbolFlags.emplace_back(WS.getName(), wasm::WASM_SYMBOL_BINDING_LOCAL);
|
|
}
|
|
|
|
{
|
|
auto HandleReloc = [&](const WasmRelocationEntry &Rel) {
|
|
// Functions referenced by a relocation need to prepared to be called
|
|
// indirectly.
|
|
const MCSymbolWasm& WS = *Rel.Symbol;
|
|
if (WS.isFunction() && IndirectSymbolIndices.count(&WS) == 0) {
|
|
switch (Rel.Type) {
|
|
case wasm::R_WEBASSEMBLY_TABLE_INDEX_I32:
|
|
case wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB:
|
|
case wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32:
|
|
case wasm::R_WEBASSEMBLY_MEMORY_ADDR_SLEB: {
|
|
uint32_t Index = SymbolIndices.find(&WS)->second;
|
|
IndirectSymbolIndices[&WS] = TableElems.size() + kInitialTableOffset;
|
|
DEBUG(dbgs() << " -> adding to table: " << TableElems.size() << "\n");
|
|
TableElems.push_back(Index);
|
|
registerFunctionType(WS);
|
|
break;
|
|
}
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
};
|
|
|
|
for (const WasmRelocationEntry &RelEntry : CodeRelocations)
|
|
HandleReloc(RelEntry);
|
|
for (const WasmRelocationEntry &RelEntry : DataRelocations)
|
|
HandleReloc(RelEntry);
|
|
}
|
|
|
|
// Translate .init_array section contents into start functions.
|
|
for (const MCSection &S : Asm) {
|
|
const auto &WS = static_cast<const MCSectionWasm &>(S);
|
|
if (WS.getSectionName().startswith(".fini_array"))
|
|
report_fatal_error(".fini_array sections are unsupported");
|
|
if (!WS.getSectionName().startswith(".init_array"))
|
|
continue;
|
|
if (WS.getFragmentList().empty())
|
|
continue;
|
|
if (WS.getFragmentList().size() != 2)
|
|
report_fatal_error("only one .init_array section fragment supported");
|
|
const MCFragment &AlignFrag = *WS.begin();
|
|
if (AlignFrag.getKind() != MCFragment::FT_Align)
|
|
report_fatal_error(".init_array section should be aligned");
|
|
if (cast<MCAlignFragment>(AlignFrag).getAlignment() != (is64Bit() ? 8 : 4))
|
|
report_fatal_error(".init_array section should be aligned for pointers");
|
|
const MCFragment &Frag = *std::next(WS.begin());
|
|
if (Frag.hasInstructions() || Frag.getKind() != MCFragment::FT_Data)
|
|
report_fatal_error("only data supported in .init_array section");
|
|
uint16_t Priority = UINT16_MAX;
|
|
if (WS.getSectionName().size() != 11) {
|
|
if (WS.getSectionName()[11] != '.')
|
|
report_fatal_error(".init_array section priority should start with '.'");
|
|
if (WS.getSectionName().substr(12).getAsInteger(10, Priority))
|
|
report_fatal_error("invalid .init_array section priority");
|
|
}
|
|
const auto &DataFrag = cast<MCDataFragment>(Frag);
|
|
const SmallVectorImpl<char> &Contents = DataFrag.getContents();
|
|
for (const uint8_t *p = (const uint8_t *)Contents.data(),
|
|
*end = (const uint8_t *)Contents.data() + Contents.size();
|
|
p != end; ++p) {
|
|
if (*p != 0)
|
|
report_fatal_error("non-symbolic data in .init_array section");
|
|
}
|
|
for (const MCFixup &Fixup : DataFrag.getFixups()) {
|
|
assert(Fixup.getKind() == MCFixup::getKindForSize(is64Bit() ? 8 : 4, false));
|
|
const MCExpr *Expr = Fixup.getValue();
|
|
auto *Sym = dyn_cast<MCSymbolRefExpr>(Expr);
|
|
if (!Sym)
|
|
report_fatal_error("fixups in .init_array should be symbol references");
|
|
if (Sym->getKind() != MCSymbolRefExpr::VK_WebAssembly_FUNCTION)
|
|
report_fatal_error("symbols in .init_array should be for functions");
|
|
auto I = SymbolIndices.find(cast<MCSymbolWasm>(&Sym->getSymbol()));
|
|
if (I == SymbolIndices.end())
|
|
report_fatal_error("symbols in .init_array should be defined");
|
|
uint32_t Index = I->second;
|
|
InitFuncs.push_back(std::make_pair(Priority, Index));
|
|
}
|
|
}
|
|
|
|
// Write out the Wasm header.
|
|
writeHeader(Asm);
|
|
|
|
writeTypeSection(FunctionTypes);
|
|
writeImportSection(Imports, DataSize, TableElems.size());
|
|
writeFunctionSection(Functions);
|
|
// Skip the "table" section; we import the table instead.
|
|
// Skip the "memory" section; we import the memory instead.
|
|
writeGlobalSection();
|
|
writeExportSection(Exports);
|
|
writeElemSection(TableElems);
|
|
writeCodeSection(Asm, Layout, Functions);
|
|
writeDataSection(DataSegments);
|
|
writeCodeRelocSection();
|
|
writeDataRelocSection();
|
|
writeLinkingMetaDataSection(DataSegments, DataSize, SymbolFlags,
|
|
InitFuncs, Comdats);
|
|
|
|
// TODO: Translate the .comment section to the output.
|
|
// TODO: Translate debug sections to the output.
|
|
}
|
|
|
|
std::unique_ptr<MCObjectWriter>
|
|
llvm::createWasmObjectWriter(std::unique_ptr<MCWasmObjectTargetWriter> MOTW,
|
|
raw_pwrite_stream &OS) {
|
|
return llvm::make_unique<WasmObjectWriter>(std::move(MOTW), OS);
|
|
}
|