From d305035155ef3d138e102434bf5a733ea2e32405 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Wed, 14 Apr 2010 04:40:28 +0000
Subject: [PATCH] implement mc asmparser support for '.', which gets the
 current PC.  rdar://7834775

We now produce an identical .o file compared to the cctools
assembler for something like this:

_f0:
L0:
        jmp L1
        .long . - L0
L1:
        jmp A
        .long . - L1

        .zerofill __DATA,_bss,A,0



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@101227 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/MC/MCParser/MCAsmLexer.h |  2 +-
 lib/MC/MCParser/AsmLexer.cpp          |  5 +++++
 lib/MC/MCParser/AsmParser.cpp         | 12 ++++++++++++
 test/MC/AsmParser/exprs.s             | 11 +++++++++++
 4 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/include/llvm/MC/MCParser/MCAsmLexer.h b/include/llvm/MC/MCParser/MCAsmLexer.h
index 043c3633086..075b69b628a 100644
--- a/include/llvm/MC/MCParser/MCAsmLexer.h
+++ b/include/llvm/MC/MCParser/MCAsmLexer.h
@@ -42,7 +42,7 @@ public:
     Plus, Minus, Tilde,
     Slash,    // '/'
     LParen, RParen, LBrac, RBrac, LCurly, RCurly,
-    Star, Comma, Dollar, Equal, EqualEqual,
+    Star, Dot, Comma, Dollar, Equal, EqualEqual,
     
     Pipe, PipePipe, Caret, 
     Amp, AmpAmp, Exclaim, ExclaimEqual, Percent, Hash,
diff --git a/lib/MC/MCParser/AsmLexer.cpp b/lib/MC/MCParser/AsmLexer.cpp
index 22c8d762df3..11833127848 100644
--- a/lib/MC/MCParser/AsmLexer.cpp
+++ b/lib/MC/MCParser/AsmLexer.cpp
@@ -74,6 +74,11 @@ AsmToken AsmLexer::LexIdentifier() {
   while (isalnum(*CurPtr) || *CurPtr == '_' || *CurPtr == '$' ||
          *CurPtr == '.' || *CurPtr == '@')
     ++CurPtr;
+  
+  // Handle . as a special case.
+  if (CurPtr == TokStart+1 && TokStart[0] == '.')
+    return AsmToken(AsmToken::Dot, StringRef(TokStart, 1));
+  
   return AsmToken(AsmToken::Identifier, StringRef(TokStart, CurPtr - TokStart));
 }
 
diff --git a/lib/MC/MCParser/AsmParser.cpp b/lib/MC/MCParser/AsmParser.cpp
index 7120d912905..e2c43f487a8 100644
--- a/lib/MC/MCParser/AsmParser.cpp
+++ b/lib/MC/MCParser/AsmParser.cpp
@@ -209,6 +209,7 @@ MCSymbol *AsmParser::CreateSymbol(StringRef Name) {
 ///  primaryexpr ::= (parenexpr
 ///  primaryexpr ::= symbol
 ///  primaryexpr ::= number
+///  primaryexpr ::= '.'
 ///  primaryexpr ::= ~,+,- primaryexpr
 bool AsmParser::ParsePrimaryExpr(const MCExpr *&Res, SMLoc &EndLoc) {
   switch (Lexer.getKind()) {
@@ -253,6 +254,17 @@ bool AsmParser::ParsePrimaryExpr(const MCExpr *&Res, SMLoc &EndLoc) {
     EndLoc = Lexer.getLoc();
     Lex(); // Eat token.
     return false;
+  case AsmToken::Dot: {
+    // This is a '.' reference, which references the current PC.  Emit a
+    // temporary label to the streamer and refer to it.
+    MCSymbol *Sym = Ctx.CreateTempSymbol();
+    Out.EmitLabel(Sym);
+    Res = MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_None, getContext());
+    EndLoc = Lexer.getLoc();
+    Lex(); // Eat identifier.
+    return false;
+  }
+      
   case AsmToken::LParen:
     Lex(); // Eat the '('.
     return ParseParenExpr(Res, EndLoc);
diff --git a/test/MC/AsmParser/exprs.s b/test/MC/AsmParser/exprs.s
index 62b11c2d4e4..d9a248cd94f 100644
--- a/test/MC/AsmParser/exprs.s
+++ b/test/MC/AsmParser/exprs.s
@@ -61,3 +61,14 @@ n:
         
         
         movw	$8, (42)+66(%eax)
+
+// "." support:
+_f0:
+L0:
+        jmp L1
+        .long . - L0
+L1:
+        jmp A
+        .long . - L1
+
+        .zerofill __DATA,_bss,A,0
-- 
2.34.1