DavidSpickett added a comment.
> I think the main reason that the RegisterInfo struct is such as it is, is
> because it wants to be trivially constructible (or whatever the c++ term for
> that is). I'm pretty sure that adding a std::string member will make it stop
> being that, and I don't think we suddenly want to run global constructors for
> all of the global RegisterInfo instances we have (and we have a lot of them).
Agreed. I think I stumbled into a solution for this for different reasons.
I might have mentioned adding a std::string somewhere in this review but I only
did that as a way to test this patch actually would work.
> If you wanted to preserve the existing patterns, the right way to store a
> string/array member inside a static struct would be to copy what is being
> done in the value_regs/invalidate_regs field, i.e., store the value itself in
> another static object, and then store the pointer to that object into
> RegisterInfo. > For dynamic RegisterInfos (like those received from the
> lldb-server), you'd use DynamicRegisterInfo and
> DynamicRegisterInfo::Register, which have logic to persist/create storage for
> these values (that logic would have to be extended to handle the new fields
> as well).
Agreed.
> That said I would *love* is someone changed the RegisterInfo structs into
> something saner, but I think that will need to be more elaborate than simply
> stuffing a std::vector member into it. I can give you my idea of how this
> could work, if you're interested in trying this out.
Sure I'd be interested in that. I've just been hacking on this small part of it
so I don't have the full picture yet.
> So I might recommend adding a RegisterInfo member that is a "Fields *fields"
> that can be easily set to NULL in POD initializers, but then stored in the
> dynamic register info class in its own vector and then have the RegisterInfo
> struct point to another POD definition of the Fields.
I though along the same lines but a different reason, I didn't want to store
empty <register flags type> in every register info that didn't have flags and
balloon the total size.
So I have:
struct RegisterInfo {
<...>
/// If not nullptr, a custom type defined by XML descriptions.
/// Using shared_ptr here means that the majority of registers that don't
have
/// custom types do not have to waste sizeof(RegisterFlags) bytes.
std::shared_ptr<RegisterFlags> flags_type = nullptr;
But shared_ptr still has a destructor. It could be `RegisterFlags*`, I just
have to work out when all that data needs to be dealocated. Probably when the
target itself destructs but I need to figure that out, in general i don't know
yet where the best place for these flags/fields to live is.
If it is a plain pointer then this patch is redundant but hey I learned how to
use placement new :)
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D134041/new/
https://reviews.llvm.org/D134041
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