[WebAssembly] Added WasmAsmParser.

Summary:
This is to replace the ELFAsmParser that WebAssembly was using, which
so far was a stub that didn't do anything, and couldn't work correctly
with wasm.

This new class is there to implement generic directives related to
wasm as a binary format. Wasm target specific directives are still
parsed in WebAssemblyAsmParser as before. The two classes now
cooperate more correctly too.

Also implemented .result which was missing. Any unknown directives
will now result in errors.

Reviewers: dschuff, sbc100

Subscribers: mgorny, jgravelle-google, eraman, aheejin, sunfish, llvm-commits

Differential Revision: https://reviews.llvm.org/D54360

llvm-svn: 346700

3 files changed, 149 insertions, 5 deletions

diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
index 3f7b507791e..7299ed29e4b 100644
--- a/llvm/lib/MC/MCParser/AsmParser.cpp
+++ b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -675,6 +675,7 @@ namespace llvm {
 extern MCAsmParserExtension *createDarwinAsmParser();
 extern MCAsmParserExtension *createELFAsmParser();
 extern MCAsmParserExtension *createCOFFAsmParser();
+extern MCAsmParserExtension *createWasmAsmParser();
 
 } // end namespace llvm
 
@@ -705,10 +706,7 @@ AsmParser::AsmParser(SourceMgr &SM, MCContext &Ctx, MCStreamer &Out,
     PlatformParser.reset(createELFAsmParser());
     break;
   case MCObjectFileInfo::IsWasm:
-    // TODO: WASM will need its own MCAsmParserExtension implementation, but
-    // for now we can re-use the ELF one, since the directives can be the
-    // same for now.
-    PlatformParser.reset(createELFAsmParser());
+    PlatformParser.reset(createWasmAsmParser());
     break;
   }
 
@@ -3921,7 +3919,7 @@ bool AsmParser::parseDirectiveCFIStartProc() {
         parseToken(AsmToken::EndOfStatement))
       return addErrorSuffix(" in '.cfi_startproc' directive");
   }
-  
+
   // TODO(kristina): Deal with a corner case of incorrect diagnostic context
   // being produced if this directive is emitted as part of preprocessor macro
   // expansion which can *ONLY* happen if Clang's cc1as is the API consumer.
diff --git a/llvm/lib/MC/MCParser/CMakeLists.txt b/llvm/lib/MC/MCParser/CMakeLists.txt
index 99fdd016799..0c54e8e9019 100644
--- a/llvm/lib/MC/MCParser/CMakeLists.txt
+++ b/llvm/lib/MC/MCParser/CMakeLists.txt
@@ -8,6 +8,7 @@ add_llvm_library(LLVMMCParser
   MCAsmParser.cpp
   MCAsmParserExtension.cpp
   MCTargetAsmParser.cpp
+  WasmAsmParser.cpp
 
   ADDITIONAL_HEADER_DIRS
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/MC/MCParser
diff --git a/llvm/lib/MC/MCParser/WasmAsmParser.cpp b/llvm/lib/MC/MCParser/WasmAsmParser.cpp
new file mode 100644
index 00000000000..93bb0cb3c72
--- /dev/null
+++ b/llvm/lib/MC/MCParser/WasmAsmParser.cpp
@@ -0,0 +1,145 @@
+//===- WasmAsmParser.cpp - Wasm Assembly Parser -----------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+// --
+//
+// 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/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;
+  MCAsmLexer *Lexer;
+
+  template<bool (WasmAsmParser::*HandlerMethod)(StringRef, SMLoc)>
+  void addDirectiveHandler(StringRef Directive) {
+    MCAsmParser::ExtensionDirectiveHandler Handler = std::make_pair(
+        this, HandleDirective<WasmAsmParser, HandlerMethod>);
+
+    getParser().addDirectiveHandler(Directive, Handler);
+  }
+
+public:
+  WasmAsmParser() : Parser(nullptr), Lexer(nullptr) {
+    BracketExpressionsSupported = true;
+  }
+
+  void Initialize(MCAsmParser &P) override {
+    Parser = &P;
+    Lexer = &Parser->getLexer();
+    // Call the base implementation.
+    this->MCAsmParserExtension::Initialize(*Parser);
+
+    addDirectiveHandler<&WasmAsmParser::parseSectionDirectiveText>(".text");
+    addDirectiveHandler<&WasmAsmParser::parseSectionDirective>(".section");
+    addDirectiveHandler<&WasmAsmParser::parseDirectiveSize>(".size");
+    addDirectiveHandler<&WasmAsmParser::parseDirectiveType>(".type");
+  }
+
+  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) Lex();
+    return ok;
+  }
+
+  bool Expect(AsmToken::TokenKind Kind, const char *KindName) {
+    if (!IsNext(Kind))
+      return Error(std::string("Expected ") + KindName + ", instead got: ",
+                   Lexer->getTok());
+    return false;
+  }
+
+  bool parseSectionDirectiveText(StringRef, SMLoc) {
+    // FIXME: .text currently no-op.
+    return false;
+  }
+
+  bool parseSectionDirective(StringRef, SMLoc) {
+    // FIXME: .section currently no-op.
+    while (Lexer->isNot(AsmToken::EndOfStatement)) Parser->Lex();
+    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 (Lexer->isNot(AsmToken::Comma))
+      return TokError("unexpected token in directive");
+    Lex();
+    const MCExpr *Expr;
+    if (Parser->parseExpression(Expr))
+      return true;
+    if (Lexer->isNot(AsmToken::EndOfStatement))
+      return TokError("unexpected token in directive");
+    Lex();
+    // MCWasmStreamer implements this.
+    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: ",
+                   Lexer->getTok());
+    auto WasmSym = cast<MCSymbolWasm>(
+                     getStreamer().getContext().getOrCreateSymbol(
+                       Lexer->getTok().getString()));
+    Lex();
+    if (!(IsNext(AsmToken::Comma) && IsNext(AsmToken::At) &&
+          Lexer->is(AsmToken::Identifier)))
+      return Error("Expected label,@type declaration, got: ", Lexer->getTok());
+    auto TypeName = Lexer->getTok().getString();
+    if (TypeName == "function")
+      WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
+    else if (TypeName == "global")
+      WasmSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL);
+    else
+      return Error("Unknown WASM symbol type: ", Lexer->getTok());
+    Lex();
+    return Expect(AsmToken::EndOfStatement, "EOL");
+  }
+};
+
+} // end anonymous namespace
+
+namespace llvm {
+
+MCAsmParserExtension *createWasmAsmParser() {
+  return new WasmAsmParser;
+}
+
+} // end namespace llvm