zahiraam added a comment. In D113107#3615372 <https://reviews.llvm.org/D113107#3615372>, @zahiraam wrote:
> In D113107#3606106 <https://reviews.llvm.org/D113107#3606106>, @rjmccall > wrote: > >> In D113107#3606094 <https://reviews.llvm.org/D113107#3606094>, @zahiraam >> wrote: >> >>> In D113107#3605797 <https://reviews.llvm.org/D113107#3605797>, @rjmccall >>> wrote: >>> >>>> I think on balance the right thing to do is probably to add an alternative >>>> to `-fexcess-precision`, like `-fexcess-precision=none`. We can default >>>> to `-fexcess-precision=standard` and treat `-fexcess-precision=fast` as an >>>> alias for `standard` for now. >>> >>> In >>> https://gcc.gnu.org/onlinedocs/gcc-4.8.2/gcc/Optimize-Options.html#index-ffloat-store-900 >>> , it looks like when compiling C, the default is >>> -fexcess-precision=standard which would align with this implementation and >>> our default too. So I think we could use the same name for the option. >>> -fexcess-precision=none corresponds to the current behavior. >>> -fexcess-precision=standard = -fexcess-precision=fast corresponds to this >>> implementation. >>> Agreed? >> >> Since you're not landing this option right now anyway, do you mind broaching >> this with the GCC folks, just to be good neighbors? You can just say that >> (1) Clang is looking for a way to request operation-by-operation lowering, >> (2) it feels like `-fexcess-precision` is the right option to add that to, >> (3) we don't want to tread on toes by adding an alternative to "their" >> option without talking to them first, and (4) what do they think about >> "none"? > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106117 In GCC using no -fexcess-precision is the same than using -fexcess-precision=standard. The patch we are proposing here is implementing this part. So for a + b + c, we are generating (_Float16) [((float a) + (float b)) + (float c)] In GCC using -fexcess-precision=16 is generating yet another flavor of the operation-by-operation emulation. For the same addition than above, gcc is generating (_Float16) [(float) (_Float16) ((float a) + (float b)) + (float c)]. That's different than our current implementation. See https://godbolt.org/z/aM8fzTsj1 Am I understanding correctly? @pengfei you are interested in the -fexcess-precision=16 part of this right? @rjmccall what do yo think? CHANGES SINCE LAST ACTION https://reviews.llvm.org/D113107/new/ https://reviews.llvm.org/D113107 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
