Add 'notail' marker for call instructions.

This marker prevents optimization passes from adding 'tail' or
'musttail' markers to a call. Is is used to prevent tail call
optimization from being performed on the call.

rdar://problem/22667622

Differential Revision: http://reviews.llvm.org/D12923

llvm-svn: 252368

7 files changed, 13 insertions, 3 deletions

diff --git a/llvm/lib/AsmParser/LLLexer.cpp b/llvm/lib/AsmParser/LLLexer.cpp
index 82d6eb7788c..91ce1fd7669 100644
--- a/llvm/lib/AsmParser/LLLexer.cpp
+++ b/llvm/lib/AsmParser/LLLexer.cpp
@@ -527,6 +527,7 @@ lltok::Kind LLLexer::LexIdentifier() {
   KEYWORD(caller);
   KEYWORD(tail);
   KEYWORD(musttail);
+  KEYWORD(notail);
   KEYWORD(target);
   KEYWORD(triple);
   KEYWORD(unwind);
diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index 7feb99d555c..aabd9716118 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -4830,6 +4830,7 @@ int LLParser::ParseInstruction(Instruction *&Inst, BasicBlock *BB,
   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);
diff --git a/llvm/lib/AsmParser/LLToken.h b/llvm/lib/AsmParser/LLToken.h
index ecd6481e6fa..6980790c098 100644
--- a/llvm/lib/AsmParser/LLToken.h
+++ b/llvm/lib/AsmParser/LLToken.h
@@ -54,6 +54,7 @@ namespace lltok {
     kw_caller,
     kw_tail,
     kw_musttail,
+    kw_notail,
     kw_target,
     kw_triple,
     kw_unwind,
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index bc846192fcf..a0029b26ff9 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -5002,6 +5002,8 @@ std::error_code BitcodeReader::parseFunctionBody(Function *F) {
         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;
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 941e54765f5..b88e55c92cb 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -2131,7 +2131,8 @@ static void WriteInstruction(const Instruction &I, unsigned InstID,
 
     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
 
diff --git a/llvm/lib/IR/AsmWriter.cpp b/llvm/lib/IR/AsmWriter.cpp
index db757508594..2f8a3406a37 100644
--- a/llvm/lib/IR/AsmWriter.cpp
+++ b/llvm/lib/IR/AsmWriter.cpp
@@ -2768,6 +2768,8 @@ void AssemblyWriter::printInstruction(const Instruction &I) {
       Out << "musttail ";
     else if (CI->isTailCall())
       Out << "tail ";
+    else if (CI->isNoTailCall())
+      Out << "notail ";
   }
 
   // Print out the opcode...
diff --git a/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp b/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
index 1eddef7ef94..7e1ba2c3c90 100644
--- a/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
@@ -304,7 +304,9 @@ bool TailCallElim::markTails(Function &F, bool &AllCallsAreTailCalls) {
       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 @@ bool TailCallElim::markTails(Function &F, bool &AllCallsAreTailCalls) {
         }
       }
 
-      if (Escaped == UNESCAPED && !Tracker.AllocaUsers.count(CI)) {
+      if (!IsNoTail && Escaped == UNESCAPED && !Tracker.AllocaUsers.count(CI)) {
         DeferredTails.push_back(CI);
       } else {
         AllCallsAreTailCalls = false;