[PATCH] AsmParser: add support for .end directive

[Saleem Abdulrasool]

The .end directive indicates the end of the file.  No further instructions are
processed after a .end directive is encountered.

One potential (glaringly obvious) optimisation that could be pursued here is to
extend MCAsmParser with a DiscardRemainder method to avoid processing lexemes to
the end of the file.  It was unclear at this point if that would be worth
adding, and could easily be added in a follow on change.


http://llvm-reviews.chandlerc.com/D2414

Files:
  lib/MC/MCParser/AsmParser.cpp
  test/MC/AsmParser/directive_end.s

Index: lib/MC/MCParser/AsmParser.cpp
===================================================================
--- lib/MC/MCParser/AsmParser.cpp
+++ lib/MC/MCParser/AsmParser.cpp
@@ -358,7 +358,8 @@
     DK_CFI_RESTORE, DK_CFI_ESCAPE, DK_CFI_SIGNAL_FRAME, DK_CFI_UNDEFINED,
     DK_CFI_REGISTER, DK_CFI_WINDOW_SAVE,
     DK_MACROS_ON, DK_MACROS_OFF, DK_MACRO, DK_ENDM, DK_ENDMACRO, DK_PURGEM,
-    DK_SLEB128, DK_ULEB128
+    DK_SLEB128, DK_ULEB128,
+    DK_END
   };
 
   /// \brief Maps directive name --> DirectiveKind enum, for
@@ -464,6 +465,9 @@
   // "align"
   bool parseDirectiveMSAlign(SMLoc DirectiveLoc, ParseStatementInfo &Info);
 
+  // "end"
+  bool parseDirectiveEnd(SMLoc DirectiveLoc);
+
   void initializeDirectiveKindMap();
 };
 }
@@ -1230,6 +1234,8 @@
     return parseDirectiveElseIf(IDLoc);
   case DK_ELSE:
     return parseDirectiveElse(IDLoc);
+  case DK_END:
+    return parseDirectiveEnd(IDLoc);
   case DK_ENDIF:
     return parseDirectiveEndIf(IDLoc);
   }
@@ -3746,6 +3752,20 @@
   return false;
 }
 
+/// parseDirectiveEnd
+/// ::= .end
+bool AsmParser::parseDirectiveEnd(SMLoc DirectiveLoc) {
+  if (getLexer().isNot(AsmToken::EndOfStatement))
+    return TokError("unexpected token in '.end' directive");
+
+  Lex();
+
+  while (Lexer.isNot(AsmToken::Eof))
+    Lex();
+
+  return false;
+}
+
 /// parseDirectiveEndIf
 /// ::= .endif
 bool AsmParser::parseDirectiveEndIf(SMLoc DirectiveLoc) {
@@ -3831,6 +3851,7 @@
   DirectiveKindMap[".ifnotdef"] = DK_IFNOTDEF;
   DirectiveKindMap[".elseif"] = DK_ELSEIF;
   DirectiveKindMap[".else"] = DK_ELSE;
+  DirectiveKindMap[".end"] = DK_END;
   DirectiveKindMap[".endif"] = DK_ENDIF;
   DirectiveKindMap[".skip"] = DK_SKIP;
   DirectiveKindMap[".space"] = DK_SPACE;
Index: test/MC/AsmParser/directive_end.s
===================================================================
--- /dev/null
+++ test/MC/AsmParser/directive_end.s
@@ -0,0 +1,11 @@
+# RUN: not llvm-mc -triple i386-unknown-unknown %s -filetype obj -o - \
+# RUN:   | llvm-readobj -t | FileCheck %s
+
+	.end
+
+its_a_tarp:
+	int $0x3
+
+# CHECK: Symbol {
+# CHECK-NOT:   Name: its_a_tarp
+
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