Phase 4 batch 3: 6 PPCBUGs in the same-shape-as-addis (4b) sub-section.
All share the pattern of computing on 64-bit values when the 32-bit ABI
requires u32 arithmetic.
- PPCBUG-001 addi: `li rT, -1` produced 0xFFFFFFFF_FFFFFFFF; now 0x00000000_FFFFFFFF.
- PPCBUG-002 addic: writeback truncated + CA from u32 unsigned compare
matching canary's `AddDidCarry`.
- PPCBUG-003 addicx: same plus CR0 i32 view (regression vs. the frozen
ppc-manual snapshot which had the correct form).
- PPCBUG-004 mulli: 64-bit signed product now truncated to 32 bits.
- PPCBUG-005 subficx: writeback + CA in u32 space; removes the bits-32-63
pollution from sign-extended negative SIMM.
- PPCBUG-007 subfcx: defensive 32-bit truncation of CA compare. Same shape
as the compare that broke addis (0x828F3F98 / 0x828F3F68 case).
Tests:
- addi_li_neg_one_zero_extends_upper (PPCBUG-001).
- addic_carry_uses_32bit_compare (PPCBUG-002).
- mulli_overflow_wraps_to_32 (PPCBUG-004).
- subficx_neg_simm_zero_extends (PPCBUG-005).
- subfcx_addis_incident_case (PPCBUG-007 — exact addis-incident case).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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