Re: ORDERED_EXPR in invert_tree_comparison

[Richard Guenther <richard.guenther@gmail.com>]

On Wed, Aug 1, 2012 at 9:21 PM, Marc Glisse <marc.glisse@inria.fr> wrote:
> Hello,
>
> an opinion on this?
>
> (I just noticed: I'll update the list in the comment visible at the top of
> the patch if this gets in).

It looks ok to me but I am no floating-point expert.  Can you add a testcase?

Ok with that change.

Thanks,
Richard.

>
> On Thu, 19 Jul 2012, Marc Glisse wrote:
>
>> Hello,
>>
>> the simple patch below passes the testsuite after a c,c++ bootstrap
>> without new regressions. Note however that
>>
>> #include <math.h>
>> int f(double a, double b){
>>  return (!isunordered(a,b))&&(a<b);
>> }
>>
>> is then optimized by ifcombine to "return (a<b);", which seems wrong in
>> the absence of -fno-trapping-math. I don't know if there are ways to trigger
>> this latent bug without the patch.
>>
>>
>>
>> 2012-06-15  Marc Glisse  <marc.glisse@inria.fr>
>>
>>        PR tree-optimization/53805
>>        * fold-const.c (invert_tree_comparison): Do invert ORDERED_EXPR and
>>        UNORDERED_EXPR for floating point.
>>
>> --- fold-const.c        (revision 189622)
>> +++ fold-const.c        (working copy)
>> @@ -2096,13 +2096,14 @@ pedantic_non_lvalue_loc (location_t loc,
>>    It is generally not safe to do this for floating-point comparisons,
>> except
>>    for EQ_EXPR and NE_EXPR, so we return ERROR_MARK in this case.  */
>>
>> enum tree_code
>> invert_tree_comparison (enum tree_code code, bool honor_nans)
>> {
>> -  if (honor_nans && flag_trapping_math && code != EQ_EXPR && code !=
>> NE_EXPR)
>> +  if (honor_nans && flag_trapping_math && code != EQ_EXPR && code !=
>> NE_EXPR
>> +      && code != ORDERED_EXPR && code != UNORDERED_EXPR)
>>     return ERROR_MARK;
>>
>>   switch (code)
>>     {
>>     case EQ_EXPR:
>>       return NE_EXPR;
>
>
> --
> Marc Glisse