On Fri, 12 Jul 2019, Richard Sandiford wrote: > At least AIUI, __builtin_isunordered etc. don't raise an exception even > for signalling NaNs.
__builtin_isunordered should raise "invalid" for signaling NaNs. (isunordered is the IEEE 754 operation compareQuietUnordered, and IEEE 754 specifies for comparisons that "Invalid operation is the only exception that a comparison predicate can signal. All predicates signal the invalid operation exception on signaling NaN operands. The predicates named Quiet shall not signal any exception, unless an operand is a signaling NaN. The predicates named Signaling shall signal the invalid operation exception on quiet NaN operands.".) Note that __builtin_isunordered (x, x) is thus not the same as __builtin_isnan (x), because isnan binds to isNaN and isNaN is a non-computational operation for which IEEE 754 specifies "Implementations shall provide the following non-computational operations for all supported arithmetic formats and should provide them for all supported interchange formats. They are never exceptional, even for signaling NaNs.". -- Joseph S. Myers jos...@codesourcery.com
