Instead of a primary opcode lookup table with 64 entries and a few
smaller tables with 4-2048 entries, use a single 64 * 2048 (128K)
entry table to dispatch opcodes.
Helps with performance, since we avoid the function call overhead for
some frequently-used instructions (e.g. branch, integer, floating point).
Saves ~2 seconds from the time to Welcome to Macintosh (same measurement
methodology as #125)
Secondarily also makes opcode registration/decoding a bit more uniform,
and scannable, since it's now all in initialize_ppc_opcode_table.
Before f65f9b9845ddf0a4050213cc36ef43c9c852a6c7 this would happen
automatically (since the stream member was always valid). It's now a
unique_ptr that's only initialized when the file is opened, so we need
to add guards for all the operations.
Adds support for a --deterministic command-line option that makes
repeated runs the same:
- Keyboard and mouse input is ignored
- The sound server does a periodic pull from the DMA channel (so that
it gets drained), but only does so via a periodic timer (instead of
being driven by a cubeb callback, which could arrive at different
times)
- Disk image writes are disabled (reads of a modified area still
work via an in-memory copy)
- NVRAM writes are disabled
- The current time that ViaCuda initializes the guest OS is always the
same.
This makes execution exactly the same each time, which should
make debugging of more subtle issues easier.
To validate that the deterministic mode is working, I've added a
periodic log of the current "time" (measured in cycle count), PC
and opcode. When comparing two runs with --log-no-uptime, the generated
log files are identical.
size_t and off_t are 32-bit values in Emscripten, which causes issues
with disk images larger than 4GB. Use the explicit type (which is more
consistent with the rest of the codebase anyway).
Allows different implementations for different platforms (the JS
build relies on browser APIs to stream disk images over the network).
Setting aside the JS build, this also reduces some code duplication.
