On Sat, Apr 12, 2014 at 12:53:45AM +0200, Hannes Frederic Sowa wrote: > Hi! > > On Tue, Oct 29, 2013 at 10:41:56AM +0100, Richard Biener wrote: > > For a "quick" GCC implementation of the builtins you could expand > > them to a open-coded sequence during gimplification. But due to > > the issues pointed out above I'm not sure it is the best interface > > to support (though now the names are taken). > > I played around with gcc internals for the first time today and came > up with this. As this is my first patch to gcc I am very happy to hear > feedback. Thanks! > Did you looked at resulting assembly for simple expressions?
Also Paul Eggert suggested at another list[1] to implement these with 128bit arithmetic which gcc can optimize quite well, it uses overflow flag as check. Could these builtins use a 128bit arithmetic as well? P.S. A generated code is affected by generic gcc bug that gcc uses conditional move instruction even when branch is very unlikely and jump would be faster. [1] https://sourceware.org/ml/libc-alpha/2013-12/msg00084.html
