On Tue, 11 May 2021, David Brown wrote: > It is also worth noting that gcc already has support for saturating > types on some targets: > > <https://gcc.gnu.org/onlinedocs/gcc/Fixed-Point.html> > > My testing of these (quite a long time ago) left me with a feeling that > it was not a feature anyone had worked hard to optimise - certainly it
The implementation isn't well-integrated with any optimizations for arithmetic on ordinary integer types / modes, because it has its own completely separate machine modes and operations on those. I still think it would be better to have a GIMPLE pass that lowers from fixed-point types to saturating etc. operations on ordinary integer types, as I said in <https://gcc.gnu.org/legacy-ml/gcc-patches/2011-05/msg00846.html>. Note however that such lowering should be more or less independent of what's being discussed in this thread - this thread is about better optimization of such operations on ordinary types (with or without built-in functions of some kind in addition to recognition of such operations written in generic C), which you can do independently of what's done with fixed-point types. -- Joseph S. Myers jos...@codesourcery.com
