The previous code had some minor issues with it, really not a big deal,
but amending it is basically 'free', so I figured, "why not?".
With the standard container maps, when:
map[key] = thing;
is done, this can cause potentially undesirable behavior in certain
scenarios. In particular, if there's no value associated with the key,
then the map constructs a default initialized instance of the value
type.
In this case, since it's a std::shared_ptr (as a type alias) that is
the value type, this will construct a std::shared_pointer, and then
assign over it (with objects that are quite large, or actively heap
allocate this can be extremely undesirable).
We also make the function take the region by value, as we can avoid a
copy (and by extension with std::shared_ptr, a copy causes an atomic
reference count increment), in certain scenarios when ownership isn't a
concern (i.e. when ReserveGlobalRegion is called with an rvalue
reference, then no copy at all occurs). So, it's more-or-less a "free"
gain without many downsides.
Instead of holding a reference that will get invalidated by
dma_pushbuffer.pop(), hold it as a copy. This doesn't have any
performance cost since CommandListHeader is 8 bytes long.
There's no real need to use a shared lifetime here, since we don't
actually expose them to anything else. This is also kind of an
unnecessary use of the heap given the objects themselves are so small;
small enough, in fact that changing over to optionals actually reduces
the overall size of the HLERequestContext struct (818 bytes to 808
bytes).
For whatever bizarre reason, Apple only made a few of std::optional's
member functions available on newer SDK versions. Given we can't even
run yuzu on macOS, and we keep the builder around to ensure that it
always at least compiles on macOS, we can bump this up a version.
This makes the class much more flexible and doesn't make performing
copies with classes that contain a bitfield member a pain.
Given BitField instances are only intended to be used within unions, the
fact the full storage value would be copied isn't a big concern (only
sizeof(union_type) would be copied anyways).
While we're at it, provide defaulted move constructors for consistency.
Because of the recent separation of GPU functionality into sync/async
variants, we need to mark the destructor virtual to provide proper
destruction behavior, given we use the base class within the System
class.
Prior to this, it was undefined behavior whether or not the destructor
in the derived classes would ever execute.
This will be utilized by more than just that class in the future. This
also renames it from OpusHeader to OpusPacketHeader to be more specific
about what kind of header it is.
