Index: include/llvm/IR/Instructions.h
===================================================================
--- include/llvm/IR/Instructions.h
+++ include/llvm/IR/Instructions.h
@@ -1489,16 +1489,21 @@
   }
 
   // Note that 'musttail' implies 'tail'.
-  enum TailCallKind { TCK_None = 0, TCK_Tail = 1, TCK_MustTail = 2 };
+  enum TailCallKind { TCK_None = 0, TCK_Tail = 1, TCK_MustTail = 2,
+                      TCK_NoTail = 3 };
   TailCallKind getTailCallKind() const {
     return TailCallKind(getSubclassDataFromInstruction() & 3);
   }
   bool isTailCall() const {
-    return (getSubclassDataFromInstruction() & 3) != TCK_None;
+    unsigned Kind = getSubclassDataFromInstruction() & 3;
+    return Kind == TCK_Tail || Kind == TCK_MustTail;
   }
   bool isMustTailCall() const {
     return (getSubclassDataFromInstruction() & 3) == TCK_MustTail;
   }
+  bool isNoTailCall() const {
+    return (getSubclassDataFromInstruction() & 3) == TCK_NoTail;
+  }
   void setTailCall(bool isTC = true) {
     setInstructionSubclassData((getSubclassDataFromInstruction() & ~3) |
                                unsigned(isTC ? TCK_Tail : TCK_None));
Index: lib/AsmParser/LLLexer.cpp
===================================================================
--- lib/AsmParser/LLLexer.cpp
+++ lib/AsmParser/LLLexer.cpp
@@ -527,6 +527,7 @@
   KEYWORD(caller);
   KEYWORD(tail);
   KEYWORD(musttail);
+  KEYWORD(notail);
   KEYWORD(target);
   KEYWORD(triple);
   KEYWORD(unwind);
Index: lib/AsmParser/LLParser.cpp
===================================================================
--- lib/AsmParser/LLParser.cpp
+++ lib/AsmParser/LLParser.cpp
@@ -4831,6 +4831,7 @@
   case lltok::kw_call:     return ParseCall(Inst, PFS, CallInst::TCK_None);
   case lltok::kw_tail:     return ParseCall(Inst, PFS, CallInst::TCK_Tail);
   case lltok::kw_musttail: return ParseCall(Inst, PFS, CallInst::TCK_MustTail);
+  case lltok::kw_notail:   return ParseCall(Inst, PFS, CallInst::TCK_NoTail);
   // Memory.
   case lltok::kw_alloca:         return ParseAlloc(Inst, PFS);
   case lltok::kw_load:           return ParseLoad(Inst, PFS);
Index: lib/AsmParser/LLToken.h
===================================================================
--- lib/AsmParser/LLToken.h
+++ lib/AsmParser/LLToken.h
@@ -54,6 +54,7 @@
     kw_caller,
     kw_tail,
     kw_musttail,
+    kw_notail,
     kw_target,
     kw_triple,
     kw_unwind,
Index: lib/Bitcode/Reader/BitcodeReader.cpp
===================================================================
--- lib/Bitcode/Reader/BitcodeReader.cpp
+++ lib/Bitcode/Reader/BitcodeReader.cpp
@@ -4905,6 +4905,8 @@
         TCK = CallInst::TCK_Tail;
       if (CCInfo & (1 << 14))
         TCK = CallInst::TCK_MustTail;
+      if (CCInfo & (1 << 16))
+        TCK = CallInst::TCK_NoTail;
       cast<CallInst>(I)->setTailCallKind(TCK);
       cast<CallInst>(I)->setAttributes(PAL);
       break;
Index: lib/Bitcode/Writer/BitcodeWriter.cpp
===================================================================
--- lib/Bitcode/Writer/BitcodeWriter.cpp
+++ lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -2130,7 +2130,8 @@
 
     Vals.push_back(VE.getAttributeID(CI.getAttributes()));
     Vals.push_back((CI.getCallingConv() << 1) | unsigned(CI.isTailCall()) |
-                   unsigned(CI.isMustTailCall()) << 14 | 1 << 15);
+                   unsigned(CI.isMustTailCall()) << 14 | 1 << 15 |
+                   unsigned(CI.isNoTailCall()) << 16);
     Vals.push_back(VE.getTypeID(FTy));
     PushValueAndType(CI.getCalledValue(), InstID, Vals, VE);  // Callee
 
Index: lib/IR/AsmWriter.cpp
===================================================================
--- lib/IR/AsmWriter.cpp
+++ lib/IR/AsmWriter.cpp
@@ -2769,6 +2769,8 @@
       Out << "musttail ";
     else if (CI->isTailCall())
       Out << "tail ";
+    else if (CI->isNoTailCall())
+      Out << "notail ";
   }
 
   // Print out the opcode...
Index: lib/Transforms/Scalar/TailRecursionElimination.cpp
===================================================================
--- lib/Transforms/Scalar/TailRecursionElimination.cpp
+++ lib/Transforms/Scalar/TailRecursionElimination.cpp
@@ -304,7 +304,9 @@
       if (!CI || CI->isTailCall())
         continue;
 
-      if (CI->doesNotAccessMemory()) {
+      bool IsNoTail = CI->isNoTailCall();
+
+      if (!IsNoTail && CI->doesNotAccessMemory()) {
         // A call to a readnone function whose arguments are all things computed
         // outside this function can be marked tail. Even if you stored the
         // alloca address into a global, a readnone function can't load the
@@ -332,7 +334,7 @@
         }
       }
 
-      if (Escaped == UNESCAPED && !Tracker.AllocaUsers.count(CI)) {
+      if (!IsNoTail && Escaped == UNESCAPED && !Tracker.AllocaUsers.count(CI)) {
         DeferredTails.push_back(CI);
       } else {
         AllCallsAreTailCalls = false;
Index: test/Bitcode/compatibility.ll
===================================================================
--- test/Bitcode/compatibility.ll
+++ test/Bitcode/compatibility.ll
@@ -1142,6 +1142,13 @@
   ret void
 }
 
+define void @instructions.call_notail() {
+  notail call void @f1()
+  ; CHECK: notail call void @f1()
+
+  ret void
+}
+
 define void @instructions.landingpad() personality i32 -2 {
   invoke void @llvm.donothing() to label %proceed unwind label %catch1
   invoke void @llvm.donothing() to label %proceed unwind label %catch2
Index: test/Bitcode/notail.ll
===================================================================
--- /dev/null
+++ test/Bitcode/notail.ll
@@ -0,0 +1,10 @@
+; RUN: llvm-as < %s | llvm-dis | FileCheck %s
+
+; CHECK: notail call void @callee()
+
+define void @foo1() {
+  notail call void @callee()
+  ret void
+}
+
+declare void @callee()
Index: test/Transforms/TailCallElim/notail.ll
===================================================================
--- /dev/null
+++ test/Transforms/TailCallElim/notail.ll
@@ -0,0 +1,24 @@
+; RUN: opt < %s -tailcallelim -S | FileCheck %s
+
+; CHECK: tail call void @callee0()
+; CHECK: notail call void @callee1()
+
+define void @foo1(i32 %a) {
+entry:
+  %tobool = icmp eq i32 %a, 0
+  br i1 %tobool, label %if.else, label %if.then
+
+if.then:
+  call void @callee0()
+  br label %if.end
+
+if.else:
+  notail call void @callee1()
+  br label %if.end
+
+if.end:
+  ret void
+}
+
+declare void @callee0()
+declare void @callee1()