On Sat, 8 Jul 2017, Yuri Gribov wrote: > On Fri, Jul 7, 2017 at 11:51 PM, Joseph Myers <jos...@codesourcery.com> wrote: > > On Fri, 7 Jul 2017, Yuri Gribov wrote: > > > >> > I suspect infinities would already work with the patch as-is (the logic > >> > dealing with constants outside the range of the integer type). I'm less > >> > clear that NaNs would work properly. (If the comparison is == or != you > >> > can optimize it for quiet NaNs, to false and true respectively. If it's > >> > a > >> > signaling NaN, or < <= > >=, optimizing to false is only valid with > >> > -fno-trapping-math, as it would lose an "invalid" exception.) > >> > >> It's actually under -fsignaling-nans (which if off by default). I've > > > > No, ordered comparisons with qNaNs should result in exceptions, > > I assume you mean sNaNs.
No, I mean qNaNs, as I said. Any of < <= > >= with a NaN argument, whether quiet or signaling, raise "invalid"; == and != only raise "invalid" for sNaNs, not qNaNs. (For a few architectures this is broken in GCC; see bug 52451 for x86, 58684 for powerpc, 77918 for s390. We should not introduce more instances of such breakage, and should fix it where it exists.) -- Joseph S. Myers jos...@codesourcery.com
