https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107608
--- Comment #45 from Richard Biener <rguenth at gcc dot gnu.org> --- (In reply to Xi Ruoyao from comment #44) > (In reply to rguent...@suse.de from comment #43) > > On Thu, 19 Jan 2023, xry111 at gcc dot gnu.org wrote: > > > > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107608 > > > > > > --- Comment #42 from Xi Ruoyao <xry111 at gcc dot gnu.org> --- > > > (In reply to Richard Biener from comment #41) > > > > We could fix the testcase with > > > > > > > > diff --git a/gcc/testsuite/gcc.dg/pr95115.c > > > > b/gcc/testsuite/gcc.dg/pr95115.c > > > > index 69c4f83250c..09273e445d2 100644 > > > > --- a/gcc/testsuite/gcc.dg/pr95115.c > > > > +++ b/gcc/testsuite/gcc.dg/pr95115.c > > > > @@ -17,6 +17,7 @@ int > > > > main (void) > > > > { > > > > double r = x (); > > > > + volatile double rr = r; > > > > if (!__builtin_isnan (r)) > > > > abort (); > > > > if (!fetestexcept (FE_INVALID)) > > > > > > > > that preserves optimizing the isnan check but also preserves the > > > > computation > > > > and checks the non-propagation of a NaN. > > > > > > Hmm, so it means we cannot rely on Inf / Inf to raise an exception? Then > > > we > > > need to fix Glibc... > > > > If the result is unused then no, GCC will happily elide exceptions from > > unused computations like Inexact from the statement > > > > 1./3.; > > > > but this has been done before. What's new is that GCC can now elide > > some uses (in this case the isnan check is the only use) > > The should we just change PR95115 to "INVALID" and remove the test case, and > fix any regression on Glibc side? I think we should adjust the testcase with a volatile like I suggested above so we verify that we don't eliminate the computation with a "constant" NaN.
