Remove DisableTailCalls from TargetOptions and the code in resetTargetOptions

that was resetting it.

Remove the uses of DisableTailCalls in subclasses of TargetLowering and use
the value of function attribute "disable-tail-calls" instead. Also,
unconditionally add pass TailCallElim to the pipeline and check the function
attribute at the start of runOnFunction to disable the pass on a per-function
basis. 
 
This is part of the work to remove TargetMachine::resetTargetOptions, and since
DisableTailCalls was the last non-fast-math option that was being reset in that
function, we should be able to remove the function entirely after the work to
propagate IR-level fast-math flags to DAG nodes is completed.

Out-of-tree users should remove the uses of DisableTailCalls and make changes
to attach attribute "disable-tail-calls"="true" or "false" to the functions in
the IR.

rdar://problem/13752163

Differential Revision: http://reviews.llvm.org/D10099

llvm-svn: 239427

6 files changed, 19 insertions, 10 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index 47c8400a668..2cfbc39a05b 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -1483,9 +1483,10 @@ ARMTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
   bool isStructRet    = (Outs.empty()) ? false : Outs[0].Flags.isSRet();
   bool isThisReturn   = false;
   bool isSibCall      = false;
+  auto Attr = MF.getFunction()->getFnAttribute("disable-tail-calls");
 
   // Disable tail calls if they're not supported.
-  if (!Subtarget->supportsTailCall() || MF.getTarget().Options.DisableTailCalls)
+  if (!Subtarget->supportsTailCall() || Attr.getValueAsString() == "true")
     isTailCall = false;
 
   if (isTailCall) {
@@ -2375,7 +2376,9 @@ bool ARMTargetLowering::mayBeEmittedAsTailCall(CallInst *CI) const {
   if (!Subtarget->supportsTailCall())
     return false;
 
-  if (!CI->isTailCall() || getTargetMachine().Options.DisableTailCalls)
+  auto Attr =
+      CI->getParent()->getParent()->getFnAttribute("disable-tail-calls");
+  if (!CI->isTailCall() || Attr.getValueAsString() == "true")
     return false;
 
   return !Subtarget->isThumb1Only();
diff --git a/llvm/lib/Target/Hexagon/HexagonISelLowering.cpp b/llvm/lib/Target/Hexagon/HexagonISelLowering.cpp
index 74d92aef25a..6e9e69f5a2c 100644
--- a/llvm/lib/Target/Hexagon/HexagonISelLowering.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonISelLowering.cpp
@@ -397,7 +397,9 @@ HexagonTargetLowering::LowerReturn(SDValue Chain,
 
 bool HexagonTargetLowering::mayBeEmittedAsTailCall(CallInst *CI) const {
   // If either no tail call or told not to tail call at all, don't.
-  if (!CI->isTailCall() || HTM.Options.DisableTailCalls)
+  auto Attr =
+      CI->getParent()->getParent()->getFnAttribute("disable-tail-calls");
+  if (!CI->isTailCall() || Attr.getValueAsString() == "true")
     return false;
 
   return true;
@@ -486,7 +488,8 @@ HexagonTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
   else
     CCInfo.AnalyzeCallOperands(Outs, CC_Hexagon);
 
-  if (DAG.getTarget().Options.DisableTailCalls)
+  auto Attr = MF.getFunction()->getFnAttribute("disable-tail-calls");
+  if (Attr.getValueAsString() == "true")
     isTailCall = false;
 
   if (isTailCall) {
diff --git a/llvm/lib/Target/TargetMachine.cpp b/llvm/lib/Target/TargetMachine.cpp
index 28242502ec8..04881264b4a 100644
--- a/llvm/lib/Target/TargetMachine.cpp
+++ b/llvm/lib/Target/TargetMachine.cpp
@@ -70,7 +70,6 @@ void TargetMachine::resetTargetOptions(const Function &F) const {
   RESET_OPTION(UnsafeFPMath, "unsafe-fp-math");
   RESET_OPTION(NoInfsFPMath, "no-infs-fp-math");
   RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math");
-  RESET_OPTION(DisableTailCalls, "disable-tail-calls");
 }
 
 /// getRelocationModel - Returns the code generation relocation model. The
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index e3ec288a683..88598a1ddd0 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -2233,7 +2233,9 @@ static bool IsCCallConvention(CallingConv::ID CC) {
 }
 
 bool X86TargetLowering::mayBeEmittedAsTailCall(CallInst *CI) const {
-  if (!CI->isTailCall() || getTargetMachine().Options.DisableTailCalls)
+  auto Attr =
+      CI->getParent()->getParent()->getFnAttribute("disable-tail-calls");
+  if (!CI->isTailCall() || Attr.getValueAsString() == "true")
     return false;
 
   CallSite CS(CI);
@@ -2762,8 +2764,9 @@ X86TargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
   StructReturnType SR = callIsStructReturn(Outs);
   bool IsSibcall      = false;
   X86MachineFunctionInfo *X86Info = MF.getInfo<X86MachineFunctionInfo>();
+  auto Attr = MF.getFunction()->getFnAttribute("disable-tail-calls");
 
-  if (MF.getTarget().Options.DisableTailCalls)
+  if (Attr.getValueAsString() == "true")
     isTailCall = false;
 
   if (Subtarget->isPICStyleGOT() &&
diff --git a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
index 3496a663f53..963f1bb13aa 100644
--- a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -94,7 +94,6 @@ PassManagerBuilder::PassManagerBuilder() {
     SizeLevel = 0;
     LibraryInfo = nullptr;
     Inliner = nullptr;
-    DisableTailCalls = false;
     DisableUnitAtATime = false;
     DisableUnrollLoops = false;
     BBVectorize = RunBBVectorization;
@@ -238,8 +237,7 @@ void PassManagerBuilder::populateModulePassManager(
   MPM.add(createInstructionCombiningPass());  // Combine silly seq's
   addExtensionsToPM(EP_Peephole, MPM);
 
-  if (!DisableTailCalls)
-    MPM.add(createTailCallEliminationPass()); // Eliminate tail calls
+  MPM.add(createTailCallEliminationPass()); // Eliminate tail calls
   MPM.add(createCFGSimplificationPass());     // Merge & remove BBs
   MPM.add(createReassociatePass());           // Reassociate expressions
   // Rotate Loop - disable header duplication at -Oz
diff --git a/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp b/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
index 9eef1327c3f..c7de2e2965c 100644
--- a/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
@@ -158,6 +158,9 @@ bool TailCallElim::runOnFunction(Function &F) {
   if (skipOptnoneFunction(F))
     return false;
 
+  if (F.getFnAttribute("disable-tail-calls").getValueAsString() == "true")
+    return false;
+
   bool AllCallsAreTailCalls = false;
   bool Modified = markTails(F, AllCallsAreTailCalls);
   if (AllCallsAreTailCalls)