[Bug tree-optimization/86509] New: Invalid conversion of comparison with infinity

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86509

            Bug ID: 86509
           Summary: Invalid conversion of comparison with infinity
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ubizjak at gmail dot com
  Target Milestone: ---

Following testcase, derived from testsuite/gcc.dg/torture/inf-compare-7.c fails
on alpha due to invalid conversion of (NaN != Infinity) to (NaN < Infinity):

--cut here--
#include <fenv.h>

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

volatile double x = __builtin_nan ("");
volatile int i;

int
main (void)
{
  i = x != __builtin_inf ();
  if (fetestexcept (FE_INVALID))
    abort ();
}
--cut here--

The _.optimized tree dump shows:

  x.0_1 ={v} x;
  _2 = x.0_1 > 1.79769313486231570814527423731704356798070567525844996599e+308;
  _3 = ~_2;
  _4 = (int) _3;
  i ={v} _4;

and the comparison gets compiled to:

        cmptlt/su $f12,$f11,$f10

Please note that cmptlt and cmptle insns trap with NaN argument, while cmpteq
and cmptun don't.

Please note that when using:

  i = x != 1e308;

compiler compiles via:

  x.0_1 ={v} x;
  _2 = x.0_1 !=
1.00000000000000001097906362944045541740492309677311846337e+308;
  _3 = (int) _2;
  i ={v} _3;

to
        cmpteq/su $f12,$f11,$f10

which doesn't trap.