In #135 we switched from a static OpcodeGrabber table to a
curOpcodeGrabber pointer in ppc_main_opcode. This results in an extra
indirection (as far as generated assembly having an additional load),
which reduces execution speed.
Switch to making the opcode grabber into a parameter to
ppc_main_opcode, and make ppc_exec_inner keep it up to date (via an
EXEF_OPCODE exception flag).
Also fixes FPU instructions in ppctests - we now need to set the FP
MSR bit when initializing the CPU.
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.
Replace it wth an explicit opcode parameter that is passed around. That
is both slightly easier to reason about (to trace where it comes from)
and slightly faster, since it can be read from a register.
On my machine takes booting to "Welcome to Macintosh" being output in
a verbose boot of Mac OS X 10.2.8 from 31.8s to 30.6s (average of 5
runs, measured using deterministic mode and looking at when execution
reaches PC 0x90004a88).
The first option is a flag that enables MPC601 (POWER) instructions for CPUs that are not MPC601.
This can be useful for the following reasons:
1) To produce results similar to classic Mac OS which emulates MPC601 instructions on CPUs that don't implement MPC601 instructions. This option is used to compare the risu traces produced in Mac OS 9 on a G3 or G4 with DPPC.
2) May increase performance in apps that use POWER instructions on emulated machines with CPUs that are not MPC601. It is not known if any such apps exist but there could be since Apple included MPC601 emulation in classic Mac OS.
genppctests.py
- Fix incorrect bits for some floating-point instruction opcodes or fields.
- Use separate register for FP results like DolphinPPCTests does.
- Remove extra FMULS.
- Use a regular expression for parsing ppcfloattest.txt. Don't parse the values, just put them in the output ppcloattests.csv file.
ppcfloattest.txt
- Clear crf0 and crf7 because we only care about crf1.
- Use values from DolphinPPCTests (0.0, 0.5, 1.0, 3.5, DBL_MAX, FLT_MAX, 2.4679999352, 4.9359998704, etc.). Some of the values were rounded. This will un-round them. Specify snan or qnan instead of nan.
- One of the FCMPO and FCMPU tests had qnan instead of snan input values.
ppcfloattest.csv
- Regenerate this file using the updated genppctests.py which uses the updated ppcfloattest.txt.
ppctests
- Update double_from_string to be able to parse the new values (snan, qnan, FLT_MAX, DBL_MAX).
