Fix unsound constant folding of x in [x] for NaN values#1374
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pranit0808 wants to merge 2 commits into
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Fix unsound constant folding of x in [x] for NaN values#1374pranit0808 wants to merge 2 commits into
x in [x] for NaN values#1374pranit0808 wants to merge 2 commits into
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Matching an identifier needle against a list element by name assumes the value is equal to itself, which is not true of a NaN double, so the optimizer rewrote expressions that evaluate to false into true. Limit the identifier match to the scalar types that cannot hold a NaN.
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/gcbrun |
| // and dyn, abstract, and struct types may all hold a NaN at runtime, so the check is limited | ||
| // to the scalar types which cannot, and to the aggregate types whose type parameters are | ||
| // themselves self-equal. | ||
| func isSelfEqualIdent(e ast.Expr) bool { |
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I would just pass e ast.NavigableExpr here rather than validate and return false later ... The input is guaranteed to be navigable based on the call path.
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/gcbrun |
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Constant folding rewrites
x in [x]totrueMatching the needle against a list element by identifier name assumes the value is equal to itself, which does not hold for a NaN double: with
xbound to NaN,x in [1, 2, x]evaluates tofalsebefore optimization andtrueafter. The identifier match is now limited to the scalar types that cannot carry a NaN, so dyn, double, and aggregate needles keep their runtime behavior.