On Mar 16, 2018, at 5:51 PM, Segher Boessenkool <seg...@kernel.crashing.org> wrote: > > Hi Carl, > > On Wed, Mar 14, 2018 at 08:27:08AM -0700, Carl Love wrote: >> The following patch fixes an ICE when compiling the test case >> >> gcc -mcpu=power7 builtin-fctid-fctiw-runnable.c >> >> The GCC compiler now gives a message >> >> "error: builtin function ‘__builtin_fctiw’ requires the ‘-mpower8-vector’ >> option" >> >> and exits without generating an internal error. > > This is an improvement over the ICE, for sure. > > But fctiw is an ISA 1.xx instruction already (and fctid is as well, > but explicitly undefined for 32-bit implementations until some 2.xx, > I forgot which, 2.02 I think?) > > Requiring power8 for it is weird and surprising. power8-vector doubly so. > > It does not seem to be a good idea to only enable the builtin for cases > where the current implementation is not broken. > > (The issue is that pre-power8 we do not allow SImode in FPR registers. > Which makes the current fctiw implementation fail). > > I think we have two good options: > > 1) Remove these builtins; > or > 2) Make them work. > I don't think we can remove them, as for a while they were the only way to access these instructions. We now have some vec_* intrinsics that are the preferred interfaces, but for backward compatibility I think we have to keep the old ones.
Thanks, Bill > > Segher >
