unsafe pointers with non-isbits may crash

[vtjnash]

This is dead code (generated by inference), but we should make sure codegen doesn't crash on it. The problem is we are trying to store an FCA, which is not directly quite legal.

(gdb) p jl_dump_llvm_value(src.V)
  %value_phi1 = phi { i32, {} addrspace(10)* } 
$10 = void
(gdb) p jl_(src.typ)
OpenTelemetryAPI.SpanStatus
$11 = void

oolong-dev/OpenTelemetry.jl#80 (comment)

MWE:

julia> struct AA; a::Int; b::Union{Nothing,String}; end
julia> code_llvm((String,)) do x; unsafe_store!(Ptr{AA}(1), AA(0,x)); end

[vtjnash]

aside, in v1.8, this slightly simplified MWE would generate good code from the optimizer, and it does not anymore, so this MWE was a bit harder to reproduce:

julia> code_typed(()) do; unsafe_store!(Ptr{AA}(1), AA(0,"")); end