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//===- WasmAsmParser.cpp - Wasm Assembly Parser -----------------------------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// --
// Note, this is for wasm, the binary format (analogous to ELF), not wasm,
// the instruction set (analogous to x86), for which parsing code lives in
// WebAssemblyAsmParser.
// This file contains processing for generic directives implemented using
// MCTargetStreamer, the ones that depend on WebAssemblyTargetStreamer are in
// WebAssemblyAsmParser.
#include "llvm/BinaryFormat/Wasm.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCParser/MCAsmLexer.h"
#include "llvm/MC/MCParser/MCAsmParser.h"
#include "llvm/MC/MCParser/MCAsmParserExtension.h"
#include "llvm/MC/MCSectionWasm.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCSymbolWasm.h"
#include "llvm/Support/MachineValueType.h"
using namespace llvm;
namespace {
class WasmAsmParser : public MCAsmParserExtension {
MCAsmParser *Parser = nullptr;
MCAsmLexer *Lexer = nullptr;
template<bool (WasmAsmParser::*HandlerMethod)(StringRef, SMLoc)>
void addDirectiveHandler(StringRef Directive) {
MCAsmParser::ExtensionDirectiveHandler Handler = std::make_pair(
this, HandleDirective<WasmAsmParser, HandlerMethod>);
getParser().addDirectiveHandler(Directive, Handler);
WasmAsmParser() { BracketExpressionsSupported = true; }
void Initialize(MCAsmParser &P) override {
Parser = &P;
Lexer = &Parser->getLexer();
// Call the base implementation.
bool error(const StringRef &Msg, const AsmToken &Tok) {
return Parser->Error(Tok.getLoc(), Msg + Tok.getString());
bool isNext(AsmToken::TokenKind Kind) {
auto Ok = Lexer->is(Kind);
if (Ok)
return Ok;
bool expect(AsmToken::TokenKind Kind, const char *KindName) {
if (!isNext(Kind))
return error(std::string("Expected ") + KindName + ", instead got: ",
return false;
bool parseSectionDirectiveText(StringRef, SMLoc) {
// FIXME: .text currently no-op.
return false;
bool parseSectionFlags(StringRef FlagStr, bool &Passive) {
SmallVector<StringRef, 2> Flags;
// If there are no flags, keep Flags empty
FlagStr.split(Flags, ",", -1, false);
for (auto &Flag : Flags) {
if (Flag == "passive")
Passive = true;
return error("Expected section flags, instead got: ", Lexer->getTok());
return false;
bool parseSectionDirective(StringRef, SMLoc) {
StringRef Name;
if (Parser->parseIdentifier(Name))
return TokError("expected identifier in directive");
if (expect(AsmToken::Comma, ","))
return true;
if (Lexer->isNot(AsmToken::String))
return error("expected string in directive, instead got: ", Lexer->getTok());
SectionKind Kind = StringSwitch<SectionKind>(Name)
.StartsWith(".data", SectionKind::getData())
.StartsWith(".rodata", SectionKind::getReadOnly())
.StartsWith(".text", SectionKind::getText())
.StartsWith(".custom_section", SectionKind::getMetadata());
MCSectionWasm* Section = getContext().getWasmSection(Name, Kind);
// Update section flags if present in this .section directive
bool Passive = false;
if (parseSectionFlags(getTok().getStringContents(), Passive))
return true;
if (Passive) {
if (!Section->isWasmData())
return Parser->Error(getTok().getLoc(),
"Only data sections can be passive");
if (expect(AsmToken::Comma, ",") || expect(AsmToken::At, "@") ||
expect(AsmToken::EndOfStatement, "eol"))
return true;
struct SectionType {
const char *Name;
SectionKind Kind;
static SectionType SectionTypes[] = {
{".text", SectionKind::getText()},
{".rodata", SectionKind::getReadOnly()},
{".data", SectionKind::getData()},
{".custom_section", SectionKind::getMetadata()},
// TODO: add more types.
for (size_t I = 0; I < sizeof(SectionTypes) / sizeof(SectionType); I++) {
if (Name.startswith(SectionTypes[I].Name)) {
auto WS = getContext().getWasmSection(Name, SectionTypes[I].Kind);
return false;
// Not found, just ignore this section.
// For code in a text section WebAssemblyAsmParser automatically adds
// one section per function, so they're optional to be specified with
// this directive.
return false;
// TODO: This function is almost the same as ELFAsmParser::ParseDirectiveSize
// so maybe could be shared somehow.
bool parseDirectiveSize(StringRef, SMLoc) {
StringRef Name;
if (Parser->parseIdentifier(Name))
return TokError("expected identifier in directive");
auto Sym = getContext().getOrCreateSymbol(Name);
if (expect(AsmToken::Comma, ","))
return true;
const MCExpr *Expr;
if (Parser->parseExpression(Expr))
return true;
if (expect(AsmToken::EndOfStatement, "eol"))
return true;
// This is done automatically by the assembler for functions currently,
// so this is only currently needed for data sections:
getStreamer().emitELFSize(Sym, Expr);
return false;
bool parseDirectiveType(StringRef, SMLoc) {
// This could be the start of a function, check if followed by
// "label,@function"
if (!Lexer->is(AsmToken::Identifier))
return error("Expected label after .type directive, got: ",
auto WasmSym = cast<MCSymbolWasm>(
if (!(isNext(AsmToken::Comma) && isNext(AsmToken::At) &&
return error("Expected label,@type declaration, got: ", Lexer->getTok());
auto TypeName = Lexer->getTok().getString();
if (TypeName == "function")
else if (TypeName == "global")
return error("Unknown WASM symbol type: ", Lexer->getTok());
return expect(AsmToken::EndOfStatement, "EOL");
} // end anonymous namespace
namespace llvm {
MCAsmParserExtension *createWasmAsmParser() {
return new WasmAsmParser;
} // end namespace llvm