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Date: Wed, 01 Aug 2012 19:21:00 -0000
From: Marc Glisse <marc.glisse@inria.fr>
To: gcc-patches@gcc.gnu.org
Subject: Re: ORDERED_EXPR in invert_tree_comparison
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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).

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