fix(encoder): route AND/CMN immediates through ThumbExpandImm — close the class#266
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… the class The last two unguarded data-processing immediate encoders: - AND.W immediate raw-packed i:imm3:imm8 (correct only <=0xFF, silently wrong above — the fold guard kept it in range, but the encoder itself was unsafe). - CMN.W immediate fell back to a silent 0xBF00 NOP for imm > 0xFF. Both now go through the shared `try_thumb_expand_imm` (added in #255): encode any valid modified immediate correctly, else `Err` (forcing register materialization). This closes the silent-miscompile class across the whole data-proc immediate family — AND/ORR/EOR/CMP/CMN/ADD/SUB/ADDS/SUBS now share one correct, Ok-or-Err path (#251/#253/#255/#259 lineage). Behavior-frozen: for imm <= 0xFF the encoding is byte-identical (try_thumb_expand_imm returns the same field), so the cmp/cmn/and folding output is unchanged — the three differentials stay result-identical (control_step 0x00210A55, flight_seam 0x07FDF307, div_const 338/338). Test and_cmn_immediate_thumb_expand_else_error: byte-range unchanged, a replicated modified immediate now encodes, and 0x101 errors (AND was raw-pack, CMN was a NOP). Part of #242. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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The last two unguarded data-processing immediate encoders:
i:imm3:imm8(correct only<=0xFF, silently wrong above — the fold guard kept it in range, but the encoder itself was unsafe).0xBF00NOP forimm > 0xFF.Both now go through the shared
try_thumb_expand_imm(#255): encode any valid modified immediate correctly, elseErr. This closes the silent-miscompile class across the whole data-proc immediate family — AND/ORR/EOR/CMP/CMN/ADD/SUB/ADDS/SUBS now share one correct, Ok-or-Err path (#251/#253/#255/#259 lineage).Behavior-frozen
For
imm <= 0xFFthe encoding is byte-identical (try_thumb_expand_immreturns the same field), so folding output is unchanged — the three differentials stay result-identical (control_step0x00210A55, flight_seam0x07FDF307, div_const 338/338). Testand_cmn_immediate_thumb_expand_else_error: byte-range unchanged; a replicated modified immediate now encodes;0x101errors (AND was raw-pack, CMN a NOP).Part of #242.
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