Catch more trivial tail call opportunities: no inputs and output types match.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@94804 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index f868b75..5dbe0bb 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -2246,27 +2246,35 @@
const SmallVectorImpl<ISD::OutputArg> &Outs,
const SmallVectorImpl<ISD::InputArg> &Ins,
SelectionDAG& DAG) const {
- // If -tailcallopt is specified, make fastcc functions tail-callable.
- const Function *F = DAG.getMachineFunction().getFunction();
- if (PerformTailCallOpt &&
- CalleeCC == CallingConv::Fast && F->getCallingConv() == CalleeCC)
- return true;
-
if (CalleeCC != CallingConv::Fast &&
CalleeCC != CallingConv::C)
return false;
+ // If -tailcallopt is specified, make fastcc functions tail-callable.
+ const Function *CallerF = DAG.getMachineFunction().getFunction();
+ if (PerformTailCallOpt &&
+ CalleeCC == CallingConv::Fast &&
+ CallerF->getCallingConv() == CalleeCC)
+ return true;
+
// Look for obvious safe cases to perform tail call optimization.
- // For now, only consider callees which take no arguments and no return
- // values.
+ // For now, only consider callees which take no arguments.
if (!Outs.empty())
return false;
- if (Ins.empty())
- // If the caller does not return a value, then this is obviously safe.
- return F->getReturnType()->isVoidTy();
+ // If the caller does not return a value, then this is obviously safe.
+ // This is one case where it's safe to perform this optimization even
+ // if the return types do not match.
+ const Type *CallerRetTy = CallerF->getReturnType();
+ if (CallerRetTy->isVoidTy())
+ return true;
- return false;
+ // If the return types match, then it's safe.
+ GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee);
+ if (!G) return false; // FIXME: common external symbols?
+ Function *CalleeF = cast<Function>(G->getGlobal());
+ const Type *CalleeRetTy = CalleeF->getReturnType();
+ return CallerRetTy == CalleeRetTy;
}
FastISel *