https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94852
--- Comment #6 from Ivan Sorokin <vanyacpp at gmail dot com> --- (In reply to Richard Biener from comment #1) > @item -ffloat-store > @opindex ffloat-store > Do not store floating-point variables in registers, and inhibit other > options that might change whether a floating-point value is taken from a > register or memory. > > I think it does what it says? This is a follow-up for my previous comment. Perhaps I haven't explained myself properly, let me explain why I find the existing behavior a bit confusing. >From the documentation on -ffloat-store: "This option prevents undesirable excess precision on machines such as the 68000 where the floating registers (of the 68881) keep more precision than a double is supposed to have. Similarly for the x86 architecture." When a person uses -ffloat-store the desired effect is not the additional loads/stores, but the reproducible results across different compiler version/optimization options. It just happened that the cheapest way to go so is adding additional loads/stores. I'm pretty sure most users would be in favor of removing extra loads/stores when they don't affect the results. I understand that perhaps there are reasons why -ffloat-store should work the way it works now. If this is true, I would recommend updating the documentation by reflecting the cases (if they exists) when one might want to use -ffloat-store on x86-64. From what I understand now using -ffloat-store on x86-64 is just a mistake.
