Index: llvm/trunk/lib/MC/MCParser/AsmParser.cpp
===================================================================
--- llvm/trunk/lib/MC/MCParser/AsmParser.cpp
+++ llvm/trunk/lib/MC/MCParser/AsmParser.cpp
@@ -288,6 +288,7 @@
 
 private:
   bool isAltmacroString(SMLoc &StrLoc, SMLoc &EndLoc);
+  void altMacroString(StringRef AltMacroStr, std::string &Res);
   bool parseStatement(ParseStatementInfo &Info,
                       MCAsmParserSemaCallback *SI);
   bool parseCurlyBlockScope(SmallVectorImpl<AsmRewrite>& AsmStrRewrites);
@@ -1209,6 +1210,8 @@
   const char *CharPtr = StrLoc.getPointer();
   while ((*CharPtr != '>') && (*CharPtr != '\n') &&
          (*CharPtr != '\r') && (*CharPtr != '\0')){
+	  if(*CharPtr == '!')
+		  CharPtr++;
     CharPtr++;
   }
   if (*CharPtr == '>') {
@@ -1218,6 +1221,15 @@
   return false;
 }
 
+/// \brief creating a string without the escape characters '!'.
+void AsmParser::altMacroString(StringRef AltMacroStr,std::string &Res) {
+  for (int Pos = 0; Pos < AltMacroStr.size(); Pos++) {
+    if (AltMacroStr[Pos] == '!')
+      Pos++;
+    Res += AltMacroStr[Pos];
+  }
+}
+
 /// \brief Parse an expression and return it.
 ///
 ///  expr ::= expr &&,|| expr               -> lowest.
@@ -2309,6 +2321,15 @@
                  (*(Token.getString().begin()) == '%') && Token.is(AsmToken::Integer))
               // Emit an integer value to the buffer.
               OS << Token.getIntVal();
+            // Only Token that was validated as a string and begins with '<'
+            // is considered altMacroString!!!
+            else if ((Lexer.IsaAltMacroMode()) &&
+                     (*(Token.getString().begin()) == '<') &&
+                     Token.is(AsmToken::String)) {
+              std::string Res;
+              altMacroString(Token.getStringContents(), Res);
+              OS << Res;
+            }
             // We expect no quotes around the string's contents when
             // parsing for varargs.
             else if (Token.isNot(AsmToken::String) || VarargParameter)
Index: llvm/trunk/test/MC/AsmParser/altmacro_string_escape.s
===================================================================
--- llvm/trunk/test/MC/AsmParser/altmacro_string_escape.s
+++ llvm/trunk/test/MC/AsmParser/altmacro_string_escape.s
@@ -0,0 +1,29 @@
+# RUN: llvm-mc -triple i386-linux-gnu %s| FileCheck %s
+
+.altmacro
+# single-character string escape
+# To include any single character literally in a string
+# (even if the character would otherwise have some special meaning),
+# you can prefix the character with `!'.
+# For example, you can write `<4.3 !> 5.4!!>' to get the literal text `4.3 > 5.4!'.
+
+# CHECK: workForFun:
+.macro fun1 number
+  .if \number=5
+    lableNotWork:
+  .else
+    workForFun:
+  .endif
+.endm
+
+# CHECK: workForFun2:
+.macro fun2 string
+  .if \string
+    workForFun2:
+  .else
+    notworkForFun2:
+  .endif
+.endm
+
+fun1 <5!!>
+fun2 <5!>4>