MC: Improve some diagnostics on uses of '.' pseudo-symbol.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128289 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 30 insertions, 1 deletions

diff --git a/lib/MC/MCParser/AsmParser.cpp b/lib/MC/MCParser/AsmParser.cpp
index 47d700a..19f7bd8 100644
--- a/lib/MC/MCParser/AsmParser.cpp
+++ b/lib/MC/MCParser/AsmParser.cpp
@@ -897,12 +897,19 @@ bool AsmParser::ParseStatement() {
           return TokError("unexpected token at start of statement");
       }
     }
+
+  } else if (Lexer.is(AsmToken::Dot)) {
+    // Treat '.' as a valid identifier in this context.
+    Lex();
+    IDVal = ".";
+
   } else if (ParseIdentifier(IDVal)) {
     if (!TheCondState.Ignore)
       return TokError("unexpected token at start of statement");
     IDVal = "";
   }
 
+
   // Handle conditional assembly here before checking for skipping.  We
   // have to do this so that .endif isn't skipped in a ".if 0" block for
   // example.
@@ -935,6 +942,10 @@ bool AsmParser::ParseStatement() {
     // identifier ':'   -> Label.
     Lex();
 
+    // Diagnose attempt to use '.' as a label.
+    if (IDVal == ".")
+      return Error(IDLoc, "invalid use of pseudo-symbol '.' as a label");
+
     // Diagnose attempt to use a variable as a label.
     //
     // FIXME: Diagnostics. Note the location of the definition as a label.
@@ -978,7 +989,7 @@ bool AsmParser::ParseStatement() {
       return HandleMacroEntry(IDVal, IDLoc, M);
 
   // Otherwise, we have a normal instruction or directive.
-  if (IDVal[0] == '.') {
+  if (IDVal[0] == '.' && IDVal != ".") {
     // Assembler features
     if (IDVal == ".set" || IDVal == ".equ")
       return ParseDirectiveSet(IDVal, true);
@@ -1306,6 +1317,12 @@ bool AsmParser::ParseAssignment(StringRef Name, bool allow_redef) {
   if (Lexer.isNot(AsmToken::EndOfStatement))
     return TokError("unexpected token in assignment");
 
+  // Error on assignment to '.'.
+  if (Name == ".") {
+    return Error(EqualLoc, ("assignment to pseudo-symbol '.' is unsupported "
+                            "(use '.space' or '.org').)"));
+  }
+
   // Eat the end of statement marker.
   Lex();
 
diff --git a/test/MC/AsmParser/dot-symbol.s b/test/MC/AsmParser/dot-symbol.s
new file mode 100644
index 0000000..4a38a40
--- /dev/null
+++ b/test/MC/AsmParser/dot-symbol.s
@@ -0,0 +1,12 @@
+# Historically 'as' treats '.' as a reference to the current location in
+# arbitrary contects. We don't support this in general.
+
+# RUN: not llvm-mc -triple i386-unknown-unknown %s 2> %t
+# RUN: FileCheck -input-file %t %s
+
+# CHECK: assignment to pseudo-symbol '.' is unsupported (use '.space' or '.org').
+. = . + 8
+
+# CHECK: invalid use of pseudo-symbol '.' as a label
+.:
+        .long 0