[AArch64, fast-isel] Fall back to SelectionDAG to select tail calls.

Certain functions such as objc_autoreleaseReturnValue have to be called as
tail-calls even at -O0. Since normal fast-isel doesn't emit calls as tail calls,
we have to fall back to SelectionDAG to select calls that are marked as tail.

<rdar://problem/17991614>

llvm-svn: 215600

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64FastISel.cpp b/llvm/lib/Target/AArch64/AArch64FastISel.cpp
index a59ee85423b..5459c1ba4f7 100644
--- a/llvm/lib/Target/AArch64/AArch64FastISel.cpp
+++ b/llvm/lib/Target/AArch64/AArch64FastISel.cpp
@@ -1687,10 +1687,15 @@ bool AArch64FastISel::FinishCall(CallLoweringInfo &CLI, MVT RetVT,
 
 bool AArch64FastISel::FastLowerCall(CallLoweringInfo &CLI) {
   CallingConv::ID CC  = CLI.CallConv;
+  bool IsTailCall     = CLI.IsTailCall;
   bool IsVarArg       = CLI.IsVarArg;
   const Value *Callee = CLI.Callee;
   const char *SymName = CLI.SymName;
 
+  // Allow SelectionDAG isel to handle tail calls.
+  if (IsTailCall)
+    return false;
+
   CodeModel::Model CM = TM.getCodeModel();
   // Only support the small and large code model.
   if (CM != CodeModel::Small && CM != CodeModel::Large)