AArch64: Safely handle the incoming sret call argument.

This adds a safe interface to the machine independent InputArg struct
for accessing the index of the original (IR-level) argument. When a
non-native return type is lowered, we generate the hidden
machine-level sret argument on-the-fly. Before this fix, we were
representing this argument as OrigArgIndex == 0, which is an outright
lie. In particular this crashed in the AArch64 backend where we
actually try to access the type of the original argument.

Now we use a sentinel value for machine arguments that have no
original argument index. AArch64, ARM, Mips, and PPC now check for this
case before accessing the original argument.

Fixes <rdar://19792160> Null pointer assertion in AArch64TargetLowering

llvm-svn: 229413

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 51bb7abaf65..4c26d370030 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -7673,7 +7673,8 @@ void SelectionDAGISel::LowerArguments(const Function &F) {
     ISD::ArgFlagsTy Flags;
     Flags.setSRet();
     MVT RegisterVT = TLI->getRegisterType(*DAG.getContext(), ValueVTs[0]);
-    ISD::InputArg RetArg(Flags, RegisterVT, ValueVTs[0], true, 0, 0);
+    ISD::InputArg RetArg(Flags, RegisterVT, ValueVTs[0], true,
+                         ISD::InputArg::NoArgIndex, 0);
     Ins.push_back(RetArg);
   }