AArch64/GlobalISel: Fix assert on call returning 0 sized type

[arsenm]

Summary

I don't know why this is considered valid IR, but it probably should
not be.

[arsenm]

Remove old, partial check

[aemerson]

I guess we have the types for doing pointer arithmetic. LGTM.

[arsenm]

9cdc27ffac48acfc458d4d6ae9db1f90757645a1

llvm/include/llvm/CodeGen/GlobalISel/CallLowering.h

struct ArgInfo {
     ArgInfo(ArrayRef<Register> Regs, Type *Ty,
             ArrayRef<ISD::ArgFlagsTy> Flags = ArrayRef<ISD::ArgFlagsTy>(),
             bool IsFixed = true)
         : Regs(Regs.begin(), Regs.end()), Ty(Ty),
           Flags(Flags.begin(), Flags.end()), IsFixed(IsFixed) {
       if (!Regs.empty() && Flags.empty())
         this->Flags.push_back(ISD::ArgFlagsTy());
       // FIXME: We should have just one way of saying "no register".
-      assert((Ty->isVoidTy() == (Regs.empty() || Regs[0] == 0)) &&
+      assert(((Ty->isVoidTy() || Ty->isEmptyTy()) ==
+              (Regs.empty() || Regs[0] == 0)) &&
              "only void types should have no register");
     }
 
     ArgInfo() : Ty(nullptr), IsFixed(false) {}
   };
 
   struct CallLoweringInfo {
     /// Calling convention to be used for the call.

llvm/lib/Target/AArch64/AArch64CallLowering.cpp

void AArch64CallLowering::splitToValueTypes(
 
   if (OrigArg.Ty->isVoidTy())
     return;
 
   SmallVector<EVT, 4> SplitVTs;
   SmallVector<uint64_t, 4> Offsets;
   ComputeValueVTs(TLI, DL, OrigArg.Ty, SplitVTs, &Offsets, 0);
 
+  if (SplitVTs.size() == 0)
+    return;
+
   if (SplitVTs.size() == 1) {
     // No splitting to do, but we want to replace the original type (e.g. [1 x
     // double] -> double).
     SplitArgs.emplace_back(OrigArg.Regs[0], SplitVTs[0].getTypeForEVT(Ctx),
                            OrigArg.Flags[0], OrigArg.IsFixed);
     return;
   }
 

llvm/test/CodeGen/AArch64/GlobalISel/call-translator.ll

 ; CHECK: [[HIPTR:%[0-9]+]]:_(p0) = G_FRAME_INDEX %fixed-stack.[[HI_FRAME]]
 ; CHECK: [[HI:%[0-9]+]]:_(s64) = G_LOAD [[HIPTR]](p0) :: (invariant load 8 from %fixed-stack.[[HI_FRAME]])
 define void @take_split_struct([2 x i64]* %ptr, i64, i64, i64,
                                i64, i64, i64,
                                [2 x i64] %in) {
   store [2 x i64] %in, [2 x i64]* %ptr
   ret void
 }
+
+%size0type = type { }
+declare %size0type @func.returns.size0.struct()
+
+; CHECK-LABEL: name: call_returns_size0_struct
+; CHECK: bb.1
+; CHECK-NEXT: ADJCALLSTACKDOWN
+; CHECK-NEXT: BL
+; CHECK-NEXT: ADJCALLSTACKUP
+; CHECK-NEXT: RET_ReallyLR
+define void @call_returns_size0_struct() {
+  ; FIXME: Why is this valid IR?
+  %call = call %size0type @func.returns.size0.struct()
+  ret void
+}
+
+declare [0 x i8] @func.returns.size0.array()
+
+; CHECK-LABEL: name: call_returns_size0_array
+; CHECK: bb.1
+; CHECK-NEXT: ADJCALLSTACKDOWN
+; CHECK-NEXT: BL
+; CHECK-NEXT: ADJCALLSTACKUP
+; CHECK-NEXT: RET_ReallyLR
+define void @call_returns_size0_array() {
+  ; FIXME: Why is this valid IR?
+  %call = call [0 x i8] @func.returns.size0.array()
+  ret void
+}
+
+declare [1 x %size0type] @func.returns.array.size0.struct()
+; CHECK-LABEL: name: call_returns_array_size0_struct
+; CHECK: bb.1
+; CHECK-NEXT: ADJCALLSTACKDOWN
+; CHECK-NEXT: BL
+; CHECK-NEXT: ADJCALLSTACKUP
+; CHECK-NEXT: RET_ReallyLR
+define void @call_returns_array_size0_struct() {
+  ; FIXME: Why is this valid IR?
+  %call = call [1 x %size0type] @func.returns.array.size0.struct()
+  ret void
+}