On Thu, 14 Jul 2016, Maciej W. Rozycki wrote: > 2. An idea has been proposed to have objects marked by the assembler to > indicate whether they include an FP hardware instruction or not. The > latters would automatically become don't-cares as far as NaN encoding > is concerned and if all the objects were such in a given static link, I don't think presence of FP hardware instructions is much of a guide to whether code cares about NaN encodings. I'd expect most code simply doing arithmetic not to care (that is, the same object code would work correctly on systems with either NaN encoding - given the right encodings for that system as inputs, it would produce the right encodings as outputs), while code using a NaN encoding explicitly (typically through __builtin_nan or folded 0.0 / 0.0 in a static initializer) cares even if that object does not use FP instructions. (Formally, of course code knowing the ABI can creating encodings directly, implement issignaling itself, etc., but that should be rare.) -- Joseph S. Myers joseph@xxxxxxxxxxxxxxxx
