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, 12 insertions, 6 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index 5b419a5..1258d96 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -2698,9 +2698,10 @@ PPCTargetLowering::LowerFormalArguments_64SVR4(
     unsigned ObjSize = ObjectVT.getStoreSize();
     unsigned ArgSize = ObjSize;
     ISD::ArgFlagsTy Flags = Ins[ArgNo].Flags;
-    std::advance(FuncArg, Ins[ArgNo].OrigArgIndex - CurArgIdx);
-    CurArgIdx = Ins[ArgNo].OrigArgIndex;
-
+    if (Ins[ArgNo].isOrigArg()) {
+      std::advance(FuncArg, Ins[ArgNo].getOrigArgIndex() - CurArgIdx);
+      CurArgIdx = Ins[ArgNo].getOrigArgIndex();
+    }
     // We re-align the argument offset for each argument, except when using the
     // fast calling convention, when we need to make sure we do that only when
     // we'll actually use a stack slot.
@@ -2723,6 +2724,8 @@ PPCTargetLowering::LowerFormalArguments_64SVR4(
     // FIXME the codegen can be much improved in some cases.
     // We do not have to keep everything in memory.
     if (Flags.isByVal()) {
+      assert(Ins[ArgNo].isOrigArg() && "Byval arguments cannot be implicit");
+
       if (CallConv == CallingConv::Fast)
         ComputeArgOffset();
 
@@ -3101,9 +3104,10 @@ PPCTargetLowering::LowerFormalArguments_Darwin(
     unsigned ObjSize = ObjectVT.getSizeInBits()/8;
     unsigned ArgSize = ObjSize;
     ISD::ArgFlagsTy Flags = Ins[ArgNo].Flags;
-    std::advance(FuncArg, Ins[ArgNo].OrigArgIndex - CurArgIdx);
-    CurArgIdx = Ins[ArgNo].OrigArgIndex;
-
+    if (Ins[ArgNo].isOrigArg()) {
+      std::advance(FuncArg, Ins[ArgNo].getOrigArgIndex() - CurArgIdx);
+      CurArgIdx = Ins[ArgNo].getOrigArgIndex();
+    }
     unsigned CurArgOffset = ArgOffset;
 
     // Varargs or 64 bit Altivec parameters are padded to a 16 byte boundary.
@@ -3124,6 +3128,8 @@ PPCTargetLowering::LowerFormalArguments_Darwin(
     // FIXME the codegen can be much improved in some cases.
     // We do not have to keep everything in memory.
     if (Flags.isByVal()) {
+      assert(Ins[ArgNo].isOrigArg() && "Byval arguments cannot be implicit");
+
       // ObjSize is the true size, ArgSize rounded up to multiple of registers.
       ObjSize = Flags.getByValSize();
       ArgSize = ((ObjSize + PtrByteSize - 1)/PtrByteSize) * PtrByteSize;