FnCall::toSMT asserts when allocsize(0) is used with aggregate return type

[IamYJLee]

Currently, FnCall::toSMT only supports allocsize(0) and allockind for functions returning ptr.
If a function returns { ptr, i64 }, Alive2 triggers the following assertion.

Related testcase

Transforms/InstCombine/simplify-libcalls-new.ll
https://web.ist.utl.pt/nuno.lopes/alive2/index.php?hash=c3466a6048874dbf&test=Transforms%2FInstCombine%2Fsimplify-libcalls-new.ll

Minimal reproducer

define void @src() {
  %call3 = call {ptr, i64} @__size_returning_new(i64 10) #0
  ret void
}

define void @tgt() {
  %call3 = call {ptr, i64} @__size_returning_new(i64 10) #0
  ret void
}

declare { ptr, i64 } @__size_returning_new(i64)

attributes #0 = { allocsize(0)  }

Error

Assertion failed: (getType().isPtrType()), function toSMT, file instr.cpp, line 2821.

[IamYJLee]

Actually, I’m not sure if a custom allocator can have an aggregate return type.