[Bug target/82692] New: [8 Regression] Ordered comparisons used for unordered built-ins

["jsm28 at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82692

            Bug ID: 82692
           Summary: [8 Regression] Ordered comparisons used for unordered
                    built-ins
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jsm28 at gcc dot gnu.org
                CC: ubizjak at gmail dot com
  Target Milestone: ---
            Target: x86_64-*-*

This was probably introduced by the fix for bug 52451.

With GCC mainline (tested with trunk r254025), some uses of unordered
__builtin_* wrongly use ordered comparison instructions on x86_64, so resulting
in spurious "invalid" exceptions for quiet NaN operands.  The following test
aborts when built with -O2 for x86_64-linux-gnu, but succeeds with GCC 7.  This
affects glibc's y0/y1/yn wrappers, so resulting in glibc test failures.

#include <fenv.h>

extern void abort (void);
extern void exit (int);

double __attribute__ ((noinline, noclone))
foo (double x)
{
  if (__builtin_islessequal (x, 0.0) || __builtin_isgreater (x, 1.0))
    return x + x;
  return x * x;
}

int
main (void)
{
  volatile double x = foo (__builtin_nan (""));
  if (fetestexcept (FE_INVALID))
    abort ();
  exit (0);
}