diff --git a/tools/llvm-mc/AsmCond.h b/tools/llvm-mc/AsmCond.h
new file mode 100644
index 0000000..17201b9
--- /dev/null
+++ b/tools/llvm-mc/AsmCond.h
@@ -0,0 +1,38 @@
+//===- AsmCond.h - Assembly file conditional assembly  ----------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef ASMCOND_H
+#define ASMCOND_H
+
+namespace llvm {
+
+/// AsmCond - Class to support conditional assembly
+///
+/// The conditional assembly feature (.if, .else, .elseif and .endif) is
+/// implemented with AsmCond that tells us what we are in the middle of 
+/// processing.  Ignore can be either true or false.  When true we are ignoring
+/// the block of code in the middle of a conditional.
+
+class AsmCond {
+public:
+  enum ConditionalAssemblyType {
+    NoCond,     // no conditional is being processed
+    IfCond,     // inside if conditional
+    ElseIfCond, // inside elseif conditional
+    ElseCond    // inside else conditional
+  };
+
+  ConditionalAssemblyType TheCond;
+  bool CondMet;
+  bool Ignore;
+};
+
+} // end namespace llvm
+
+#endif
diff --git a/tools/llvm-mc/AsmParser.cpp b/tools/llvm-mc/AsmParser.cpp
index 5bb1ae4..4d6fac1 100644
--- a/tools/llvm-mc/AsmParser.cpp
+++ b/tools/llvm-mc/AsmParser.cpp
@@ -45,18 +45,62 @@
   
   bool HadError = false;
   
+  AsmCond StartingCondState = TheCondState;
+
   // While we have input, parse each statement.
   while (Lexer.isNot(AsmToken::Eof)) {
+    // Handle conditional assembly here before calling ParseStatement()
+    if (Lexer.getKind() == AsmToken::Identifier) {
+      // If we have an identifier, handle it as the key symbol.
+      AsmToken ID = Lexer.getTok();
+      SMLoc IDLoc = ID.getLoc();
+      StringRef IDVal = ID.getString();
+
+      if (IDVal == ".if" ||
+          IDVal == ".elseif" ||
+          IDVal == ".else" ||
+          IDVal == ".endif") {
+        if (!ParseConditionalAssemblyDirectives(IDVal, IDLoc))
+          continue;
+	HadError = true;
+	EatToEndOfStatement();
+	continue;
+      }
+    }
+    if (TheCondState.Ignore) {
+      EatToEndOfStatement();
+      continue;
+    }
+
     if (!ParseStatement()) continue;
   
-    // If we had an error, remember it and recover by skipping to the next line.
+    // We had an error, remember it and recover by skipping to the next line.
     HadError = true;
     EatToEndOfStatement();
   }
+
+  if (TheCondState.TheCond != StartingCondState.TheCond ||
+      TheCondState.Ignore != StartingCondState.Ignore)
+    return TokError("unmatched .ifs or .elses");
   
   return HadError;
 }
 
+/// ParseConditionalAssemblyDirectives - parse the conditional assembly
+/// directives
+bool AsmParser::ParseConditionalAssemblyDirectives(StringRef Directive,
+                                                   SMLoc DirectiveLoc) {
+  if (Directive == ".if")
+    return ParseDirectiveIf(DirectiveLoc);
+  if (Directive == ".elseif")
+    return ParseDirectiveElseIf(DirectiveLoc);
+  if (Directive == ".else")
+    return ParseDirectiveElse(DirectiveLoc);
+  if (Directive == ".endif")
+    return ParseDirectiveEndIf(DirectiveLoc);
+  return true;
+}
+
 /// EatToEndOfStatement - Throw away the rest of the line for testing purposes.
 void AsmParser::EatToEndOfStatement() {
   while (Lexer.isNot(AsmToken::EndOfStatement) &&
@@ -1264,3 +1308,116 @@
 
   return false;
 }
+
+/// ParseDirectiveIf
+/// ::= .if expression
+bool AsmParser::ParseDirectiveIf(SMLoc DirectiveLoc) {
+  // Consume the identifier that was the .if directive
+  Lexer.Lex();
+
+  TheCondStack.push_back(TheCondState);
+  TheCondState.TheCond = AsmCond::IfCond;
+  if(TheCondState.Ignore) {
+    EatToEndOfStatement();
+  }
+  else {
+    int64_t ExprValue;
+    if (ParseAbsoluteExpression(ExprValue))
+      return true;
+
+    if (Lexer.isNot(AsmToken::EndOfStatement))
+      return TokError("unexpected token in '.if' directive");
+    
+    Lexer.Lex();
+
+    TheCondState.CondMet = ExprValue;
+    TheCondState.Ignore = !TheCondState.CondMet;
+  }
+
+  return false;
+}
+
+/// ParseDirectiveElseIf
+/// ::= .elseif expression
+bool AsmParser::ParseDirectiveElseIf(SMLoc DirectiveLoc) {
+  if (TheCondState.TheCond != AsmCond::IfCond &&
+      TheCondState.TheCond != AsmCond::ElseIfCond)
+      Error(DirectiveLoc, "Encountered a .elseif that doesn't follow a .if or "
+                          " an .elseif");
+  TheCondState.TheCond = AsmCond::ElseIfCond;
+
+  // Consume the identifier that was the .elseif directive
+  Lexer.Lex();
+
+  bool LastIgnoreState = false;
+  if (!TheCondStack.empty())
+      LastIgnoreState = TheCondStack.back().Ignore;
+  if (LastIgnoreState || TheCondState.CondMet) {
+    TheCondState.Ignore = true;
+    EatToEndOfStatement();
+  }
+  else {
+    int64_t ExprValue;
+    if (ParseAbsoluteExpression(ExprValue))
+      return true;
+
+    if (Lexer.isNot(AsmToken::EndOfStatement))
+      return TokError("unexpected token in '.elseif' directive");
+    
+    Lexer.Lex();
+    TheCondState.CondMet = ExprValue;
+    TheCondState.Ignore = !TheCondState.CondMet;
+  }
+
+  return false;
+}
+
+/// ParseDirectiveElse
+/// ::= .else
+bool AsmParser::ParseDirectiveElse(SMLoc DirectiveLoc) {
+  // Consume the identifier that was the .else directive
+  Lexer.Lex();
+
+  if (Lexer.isNot(AsmToken::EndOfStatement))
+    return TokError("unexpected token in '.else' directive");
+  
+  Lexer.Lex();
+
+  if (TheCondState.TheCond != AsmCond::IfCond &&
+      TheCondState.TheCond != AsmCond::ElseIfCond)
+      Error(DirectiveLoc, "Encountered a .else that doesn't follow a .if or an "
+                          ".elseif");
+  TheCondState.TheCond = AsmCond::ElseCond;
+  bool LastIgnoreState = false;
+  if (!TheCondStack.empty())
+    LastIgnoreState = TheCondStack.back().Ignore;
+  if (LastIgnoreState || TheCondState.CondMet)
+    TheCondState.Ignore = true;
+  else
+    TheCondState.Ignore = false;
+
+  return false;
+}
+
+/// ParseDirectiveEndIf
+/// ::= .endif
+bool AsmParser::ParseDirectiveEndIf(SMLoc DirectiveLoc) {
+  // Consume the identifier that was the .endif directive
+  Lexer.Lex();
+
+  if (Lexer.isNot(AsmToken::EndOfStatement))
+    return TokError("unexpected token in '.endif' directive");
+  
+  Lexer.Lex();
+
+  if ((TheCondState.TheCond == AsmCond::NoCond) ||
+      TheCondStack.empty())
+    Error(DirectiveLoc, "Encountered a .endif that doesn't follow a .if or "
+                        ".else");
+  if (!TheCondStack.empty()) {
+    TheCondState = TheCondStack.back();
+    TheCondStack.pop_back();
+  }
+
+  return false;
+}
diff --git a/tools/llvm-mc/AsmParser.h b/tools/llvm-mc/AsmParser.h
index 7a4c832..c6f6f63 100644
--- a/tools/llvm-mc/AsmParser.h
+++ b/tools/llvm-mc/AsmParser.h
@@ -14,12 +14,15 @@
 #ifndef ASMPARSER_H
 #define ASMPARSER_H
 
+#include <vector>
 #include "AsmLexer.h"
+#include "AsmCond.h"
 #include "llvm/MC/MCAsmParser.h"
 #include "llvm/MC/MCStreamer.h"
 
 namespace llvm {
 class AsmExpr;
+class AsmCond;
 class MCContext;
 class MCInst;
 class MCStreamer;
@@ -33,7 +36,10 @@
   MCContext &Ctx;
   MCStreamer &Out;
   TargetAsmParser *TargetParser;
-  
+
+  AsmCond TheCondState;
+  std::vector<AsmCond> TheCondStack;
+
 public:
   AsmParser(SourceMgr &_SM, MCContext &_Ctx, MCStreamer &_Out)
     : Lexer(_SM), Ctx(_Ctx), Out(_Out), TargetParser(0) {}
@@ -67,6 +73,8 @@
 
   bool TokError(const char *Msg);
   
+  bool ParseConditionalAssemblyDirectives(StringRef Directive,
+                                          SMLoc DirectiveLoc);
   void EatToEndOfStatement();
   
   bool ParseAssignment(const StringRef &Name, bool IsDotSet);
@@ -118,6 +126,12 @@
 
   bool ParseDirectiveAbort(); // ".abort"
   bool ParseDirectiveInclude(); // ".include"
+
+  bool ParseDirectiveIf(SMLoc DirectiveLoc); // ".if"
+  bool ParseDirectiveElseIf(SMLoc DirectiveLoc); // ".elseif"
+  bool ParseDirectiveElse(SMLoc DirectiveLoc); // ".else"
+  bool ParseDirectiveEndIf(SMLoc DirectiveLoc); // .endif
+
 };
 
 } // end namespace llvm