Fix path to xdot SDFG#5
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ThrudPrimrose
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May 21, 2026
…ening + termination cap Three correctness fixes to SymbolPropagation, surfaced by adversarial tests: 1. Same-edge race (#5): _update_syms substituted a propagated value into an outgoing edge's assignment RHS without checking the edge's own assignment keys. Interstate-edge assignments are simultaneous, so substituting e.g. `anext -> a + b` into `{b: a, a: anext}` produced `{b: a, a: a + b}` -- `a` both read and written on one edge, which validation rejects. Now each edge filters out substitutions whose value reads a symbol assigned on that edge. 2. Cross-CFG assert crash (#1): _get_in_syms `assert new_in_syms == {}` crashed on start/branch regions that already carried edge-accumulated symbols. Replaced with a conservative combine (disagreements -> None). 3. Fixpoint non-termination: the inner _update_syms `while changed` loop oscillated forever on CYCLIC symbol value dependencies (swaps). Added an iteration cap (#symbols + 2) guaranteeing termination, leaving cyclic symbols un-substituted (conservative + correct). Tests (tests/passes/symbol_propagation_hard_test.py): 21 original (incl. the co-evolving-pair regression, input fixed to a valid simultaneous edge) + 14 adversarial (10 pass). 4 cyclic-swap tests are strict-xfail pinning a remaining deeper bug: the pass over-substitutes a reassigned symbol's value into use-sites on value cycles. Existing tests/passes/symbol_propagation_test.py stays green.
ThrudPrimrose
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May 31, 2026
…ening + termination cap Three correctness fixes to SymbolPropagation, surfaced by adversarial tests: 1. Same-edge race (#5): _update_syms substituted a propagated value into an outgoing edge's assignment RHS without checking the edge's own assignment keys. Interstate-edge assignments are simultaneous, so substituting e.g. `anext -> a + b` into `{b: a, a: anext}` produced `{b: a, a: a + b}` -- `a` both read and written on one edge, which validation rejects. Now each edge filters out substitutions whose value reads a symbol assigned on that edge. 2. Cross-CFG assert crash (#1): _get_in_syms `assert new_in_syms == {}` crashed on start/branch regions that already carried edge-accumulated symbols. Replaced with a conservative combine (disagreements -> None). 3. Fixpoint non-termination: the inner _update_syms `while changed` loop oscillated forever on CYCLIC symbol value dependencies (swaps). Added an iteration cap (#symbols + 2) guaranteeing termination, leaving cyclic symbols un-substituted (conservative + correct). Tests (tests/passes/symbol_propagation_hard_test.py): 21 original (incl. the co-evolving-pair regression, input fixed to a valid simultaneous edge) + 14 adversarial (10 pass). 4 cyclic-swap tests are strict-xfail pinning a remaining deeper bug: the pass over-substitutes a reassigned symbol's value into use-sites on value cycles. Existing tests/passes/symbol_propagation_test.py stays green.
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