According to hwtests, older versions of IOS are slower at performing
various filesystem operations:
https://docs.google.com/spreadsheets/d/1OKo9IUuKCrniz4m0kYIaMP_qFtOCmAzHZ_zAmobvBcc/edit
(courtesy of JMC)
A quick glance at IOS9 reveals that older versions of IOS have a
simplistic implementation of memcpy that does not optimize large copies
by copying 16 bytes or 32 bytes per chunk, which makes cached reads
and writes noticeably slower -- the difference was significant enough
that the OoT speedrunning community noticed that IOS9 (the IOS that
is used for the OoT VC title) was slower.
More or less a complete rewrite of the function which aims
to be equally good or better for each given input, without
relying on special cases like the old implementation did.
In particular, we now have more extensive support for
MOVN, as mentioned in a TODO comment.
Instead of constructing IPCCommandResult with static member functions
in the Device class, we can just add the relevant constructors to the
reply struct itself. Makes more sense than putting it in Device
when the struct is used in the kernel code and doesn't use any Device
specific members...
This commit also changes the IPC command handlers to return an optional
IPCCommandResult rather than an IPCCommandResult. This removes the need
for a separate boolean that indicates whether the "result" is actually
a reply, and also avoids the need to set dummy result values and ticks.
It also makes it really obvious which commands can result in no reply
being generated.
Finally, this commit renames IPCCommandResult to IPCReply since the
struct is now only used for actual replies. This new name is less
verbose in my opinion.
The diff is quite large since this touches every command handler, but
the only functional change is that I fixed EnqueueIPCReply to
take a s64 for cycles_in_future to match IPCReply.
PrepareForState is now unnecessary with the new implementation of
HostFileSystem::DoState, which does what the old implementation
(CWII_IPC_HLE_Device_FileIO::PrepareForState) used to do.
I don't really see the use of this. (Maybe in the past it
was used for when we need a constant number of instructions
for backpatching? But we don't use MOVI2R for that now.)
Now that the ES class (now called ESDevice) and the ES namespace do
not conflict anymore, "IOS::" can be dropped in a lot of cases.
This also removes "IOS::HLE::" for code that is already in that
namespace. Some of those names used to be explicitly qualified
only for historical reasons.
There are no functional changes.
Some of the device names can be ambiguous and require fully or partly
qualifying the name (e.g. IOS::HLE::FS::) in a somewhat verbose way.
Additionally, insufficiently qualified names are prone to breaking.
Consider the example of IOS::HLE::FS:: (namespace) and
IOS::HLE::Device::FS (class). If we use FS::Foo in a file that doesn't
know about the class, everything will work fine. However, as soon as
Device::FS is declared via a header include or even just forward
declared, that code will cease to compile because FS:: now resolves
to Device::FS if FS::Foo was used in the Device namespace.
It also leads to having to write IOS::ES:: to access ES types and
utilities even for code that is already under the IOS namespace.
The fix for this is simple: rename the device classes and give them
a "device" suffix in their names if the existing ones may be ambiguous.
This makes it clear whether we're referring to the device class or to
something else.
This is not any longer to type, considering it lets us get rid of the
Device namespace, which is now wholly unnecessary.
There are no functional changes in this commit.
A future commit will fix unnecessarily qualified names.
Léo Lam