On Sat, Nov 4, 2023 at 9:41 AM Enrico via Gcc <gcc@gcc.gnu.org> wrote: > > Hello, > > > for a custom architecture I am working on, I would like to entirely disable > the usage of hardware floating point instructions in favor of library > methods on demand. > > I need advice on what is the best strategy to do this. My idea is to: > > - create a new flag (let's say -m[no-]float-insn or something like that
A few backends use -msoft-float to handle that. (mips and rs6000 for examples). And yes GCC outputs library calls for floating point in those cases. Thanks, Andrew > > - use the value of the flag in the condition of every define_insn in the > machine description to inhibit their usage if the flag is active > > > My questions: > > - Is this a good strategy? Or would you suggest a better solution? > > - If I switch all floating point instructions off, will GCC automatically > use their software counterpart, from the builtins or libraries, by finding > them via their instruction patterns? > > - I noticed that some opcodes of our architecture can be found in the > assembler, but they are not available in the GCC backend. How can I inhibit > the usage of those instructions? Shall I explicitly add to the machine > description and then disable them with their condition? > > > Thank you for your suggestions. > > I am new in this (difficult) business and I am trying to learn. > > > Kind regards > > Enrico Bragante
