Draft: [6502] Pass Lorenz C64 tests

[SaxxonPike]

This change makes the 6502 opcode tests (not specific to 6510 I/O behavior) pass on the M6502X CPU core:

• Fix decimal mode SBC implementation (flags improperly set)
• Add ANE implementation
• Implement SHA/SHX/SHY page correction behavior and RDY pin interaction
• Allow system cores to configure the "constant" values for ANE and LXA, this is implemented like a register that can be "read". Not all manufactured 6502 derivatives will have identical values, but should mostly be consistent among the same make and model of CPU

See more in this issue: #4176

This is a draft because we will want input from other system core developers who maintain cores that use the M6502X CPU core.

Check if completed:

• I have run any relevant test suites
• I, the committer, have read the licensing terms for contributors (last updated 2024-06-22) and am compliant

[YoshiRulz]

I believe Atari2600Hawk, A7800Hawk, and NesHawk would be the other relevant cores, and they're all maintainerless since alyosha left.

[SaxxonPike]

@YoshiRulz I will do my best to verify that these changes still satisfy existing tests that still exist (SHX/SHY/SHA is a really rare case and not super useful, doubt much commercial software uses them at all much less full on system-specific test suites)

Some links for consideration:

• A2600:
  • https://forums.atariage.com/topic/291749-seeking-emulator-test-programs/ (good list there)
• A7800:
  • https://emulation.gametechwiki.com/index.php/Atari_7800_emulators (Rikki & Vikki note, honestly there is not much for this system)
• NES:
  • https://www.nesdev.org/wiki/Emulator_tests (lots here)
  • Blargg's tests as cited by the relevant NEShawk source itself

[YoshiRulz]

https://gitlab.com/tasbot/libre-roms-ci/-/snippets

[SaxxonPike]

This makes the 1541 disk drive CPU test suite pass.


(edit: added disk 2 screenshot)