[CIR] Add integer result type for cir.global_view

[Lancern]

This PR updates the #cir.global_view attribute and make it accept integer types as its result type.

[bcardosolopes]

Sounds like this is equivalent to a global view with zero index? Why can't this be modeled ash cir.const #cir.global_view<@".str"> ?

[Lancern]

cir.global_addr is of integer types, and I'm not sure if it's appropriate to make cir.global_view an integer type. If it's OK I could just update cir.global_view instead of introducing a new one.

[bcardosolopes]

My take is that we want here is a constant pointer coming out of cir.const, followed up by a cast to integer?

[Lancern]

My take is that we want here is a constant pointer coming out of cir.const, followed up by a cast to integer?

In this case, yes. But I'm actually proposing this attribute for the following scenario where you don't have space for additional operations:

%0 = cir.const #cir.const_struct {
  #cir.global_addr @aaa,
  #cir.global_addr @bbb
}

And I'm looking at this scenario because recently I'm working on the LLVM lowering of member function pointers. Upon ABI lowering, a member function pointer is lowered to a struct with two fields of type ptrdiff_t. When the member function pointer represents a non-virtual member function, the first field stores the address of the target function as an integer. Thus to represent constant member function pointers I need an attribute that works like #cir.global_addr.

[Lancern]

I have updated this PR and removed the #cir.global_addr attribute. Instead, I just updated the existing #cir.global_view attribute and make it accept integer types as its result type.