341196a111
Xenon is a 64-bit PPC core (32-bit *pointer* ABI, but 64-bit registers and integer arithmetic). The interpreter was truncating every word-form integer ALU writeback to 32 bits and zero-extending, on a false "MSR.SF=0 / 32-bit ABI" premise. This silently corrupted any genuine 64-bit value flowing through word-form arithmetic. Confirmed load-bearing via runtime ours-vs-canary capture: Sylpheed's millisecond->LARGE_INTEGER timeout converter sub_824ACA88 does `clrldi; mulli r11,r11,-10000; std`. For a 16 ms wait the correct result is -160000 = 0xFFFFFFFF_FFFD8F00 (relative). canary stores exactly that; ours' truncating `mulli` stored 0x00000000_FFFD8F00 (positive) -> the i64 timeout read as a huge *absolute* deadline -> a ~26000x over-wait that froze the main frame loop. After the fix the timeout matches canary and the previously-frozen frame/worker loops run (parallel boot NtWaitForMultipleObjectsEx 94 -> 30428; KeWaitForSingleObject/critical-section loops resume). Fix mirrors canary's INT64 emitters (ppc_emit_alu.cc) op-by-op for the 17 data-losing word-form ops: addis, addic(.), subfic(.), mulli, add(c/e/ze/me)x, subf(c/e/ze/me)x, negx, mullwx. Only the result *writeback* widens to full 64 bit; the 32-bit carry (XER[CA]) and overflow (XER[OV]) computations and the CR0 i32 view are preserved byte-identical (the low 32 bits of the new result equal the old truncated result), so this is a strict no-op for clean 32-bit values and only restores the previously-zeroed upper bits for genuine 64-bit values. Genuinely-32-bit ops (rlwinm/slw/srw/cmpw, mulhw/divw whose upper bits are ISA-undefined) are left untouched. Updated 7 unit tests that asserted the truncation (they encoded the bug) to the canary-correct full-64-bit values. Re-baselined the sylpheed_n50m golden (imports 40454 -> 1790936: the unwedged frame/worker loops now cycle under the instruction-count timebase); sylpheed_n2m unchanged (pre-frame-loop). Lockstep determinism preserved (two 50M runs identical). Full suite 660/660. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
11 lines
182 B
JSON
11 lines
182 B
JSON
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