[Bug tree-optimization/98169] New: isnan pattern not folded

[denis.campredon at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98169

            Bug ID: 98169
           Summary: isnan pattern not folded
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: denis.campredon at gmail dot com
  Target Milestone: ---

The two following functions should produce the same assembly, at least on x86,
but for f1 gcc does not recognize the pattern for f1 and produce not optimal
code.

The problem is the same for all floating types.

bool f1(float a) {
    return a == a;
}

bool f2(float a) {
    return !__builtin_isnan(a);
}


Furthermore, for __float128, instead of calling __unordtf2 the following code
call __netf2

bool f3(__float128 a) {
    return a != a;
}