ScheduleDAGInstrs: In functions with tail calls PseudoSourceValues are not non-aliasing distinct objects

The code that builds the dependence graph assumes that two PseudoSourceValues
don't alias. In a tail calling function two FixedStackObjects might refer to the
same location. Worse 'immutable' fixed stack objects like function arguments are
not immutable and will be clobbered.

Change this so that a load from a FixedStackObject is not invariant in a tail
calling function and don't return a PseudoSourceValue for an instruction in tail
calling functions when building the dependence graph so that we handle function
arguments conservatively.

Fix for PR23459.

rdar://20740035

llvm-svn: 236916

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index cbb5a32098f..6d2a95129c3 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -2873,8 +2873,10 @@ AArch64TargetLowering::LowerCall(CallLoweringInfo &CLI,
 
   // If we're doing a tall call, use a TC_RETURN here rather than an
   // actual call instruction.
-  if (IsTailCall)
+  if (IsTailCall) {
+    MF.getFrameInfo()->setHasTailCall();
     return DAG.getNode(AArch64ISD::TC_RETURN, DL, NodeTys, Ops);
+  }
 
   // Returns a chain and a flag for retval copy to use.
   Chain = DAG.getNode(AArch64ISD::CALL, DL, NodeTys, Ops);