Handle IntrinsicInst uses in allocation optimization pass

[yuyichao]

This is needed on LLVM 5.0.

[maleadt]

This breaks my (possibly invalid) use of pointer_from_objref: https://github.com/JuliaGPU/CUDAdrv.jl/blob/fc18bbad0c2286cbd42b2bc8b101663b18df38c5/src/execution.jl#L81-L85

MWE:

function foo(obj)
    ptr = Base.pointer_from_objref(obj)
    println("Located at: ", ptr)
    println("Which contains: ", Base.unsafe_pointer_to_objref(ptr))

end

const obj = Ptr{Void}(1)
println("Original object: ", obj)
foo(obj)

Before this PR:

Original object: Ptr{Void} @0x0000000000000001
Located at: Ptr{Void} @0x00007fab0326a770
Which contains: Ptr{Void} @0x0000000000000001

But now segfaults on the unsafe_pointer_to_objref.
Still works interpreted, so I assume this is not intended.

[yuyichao]

This is intended. Calling pointer_from_objref on a isbits object has always been invalid.

[maleadt]

Okay, I think I can have a correct solution using Ref boxes. But as I need to pass an array of pointers, I'm doing unsafe_convert(Ptr{Void}, ref) which the GC can't track, so I assume I need the new @gc_preserve for that. But your pass can't handle that intrinsic, it trips up on:
%300 = call token (...) @llvm.julia.gc_preserve_begin(%jl_value_t addrspace(10)* %258, %jl_value_t addrspace(10)* %267, %jl_value_t addrspace(10)* %276), !dbg !162
at

julia/src/llvm-alloc-opt.cpp

Line 452 in 809b79e

assert(ID);

[yuyichao]

it trips up on:
%300 = call token (...) @llvm.julia.gc_preserve_begin(%jl_value_t addrspace(10)* %258, %jl_value_t addrspace(10)* %267, %jl_value_t addrspace(10)* %276), !dbg !162

..... OK, this is because Keno is lying to me ;-p..... Will fix later....

[vtjnash]

http:https://llvm.org/doxygen/Function_8h_source.html#l00178 😛