[WebAssembly] Fixed objdump not parsing function headers.

Summary:
objdump was interpreting the function header containing the locals
declaration as instructions. To parse these without injecting target
specific code in objdump, MCDisassembler::onSymbolStart was added to
be implemented by the WebAssembly implemention.

WasmObjectFile now returns a code offset for the "address" of a symbol,
rather than the index. This is also more in-line with what other
targets do.

Also ensured that the AsmParser correctly puts each function
in its own segment to enable this test case.

Reviewers: sbc100, dschuff

Subscribers: jgravelle-google, aheejin, sunfish, rupprecht, llvm-commits

Differential Revision: https://reviews.llvm.org/D56684

llvm-svn: 351460

1 files changed, 15 insertions, 8 deletions

diff --git a/llvm/lib/MC/MCParser/WasmAsmParser.cpp b/llvm/lib/MC/MCParser/WasmAsmParser.cpp
index 93bb0cb3c72..9c41c474dae 100644
--- a/llvm/lib/MC/MCParser/WasmAsmParser.cpp
+++ b/llvm/lib/MC/MCParser/WasmAsmParser.cpp
@@ -22,6 +22,7 @@
 #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"
@@ -83,8 +84,16 @@ public:
   }
 
   bool parseSectionDirective(StringRef, SMLoc) {
-    // FIXME: .section currently no-op.
-    while (Lexer->isNot(AsmToken::EndOfStatement)) Parser->Lex();
+    StringRef Name;
+    if (Parser->parseIdentifier(Name))
+      return TokError("expected identifier in directive");
+    // FIXME: currently requiring this very fixed format.
+    if (Expect(AsmToken::Comma, ",") || Expect(AsmToken::String, "string") ||
+        Expect(AsmToken::Comma, ",") || Expect(AsmToken::At, "@") ||
+        Expect(AsmToken::EndOfStatement, "eol"))
+      return true;
+    auto WS = getContext().getWasmSection(Name, SectionKind::getText());
+    getStreamer().SwitchSection(WS);
     return false;
   }
 
@@ -95,15 +104,13 @@ public:
     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();
+    if (Expect(AsmToken::Comma, ","))
+      return true;
     const MCExpr *Expr;
     if (Parser->parseExpression(Expr))
       return true;
-    if (Lexer->isNot(AsmToken::EndOfStatement))
-      return TokError("unexpected token in directive");
-    Lex();
+    if (Expect(AsmToken::EndOfStatement, "eol"))
+      return true;
     // MCWasmStreamer implements this.
     getStreamer().emitELFSize(Sym, Expr);
     return false;