Re: [patch] Fix failure of ACATS c45503c at -O2

[Jeff Law <law@redhat.com>]

On 10/20/2015 10:33 AM, Eric Botcazou wrote:
> Hi,
>
> this test started to fail recently as the result of the work of Richard S.,
> but the underlying issue had been latent for a long time.  It boils down to
> this excerpt from the VRP1 dump file:
>
> Found new range for _9: [0, 12]
> marking stmt to be not simulated again
>
> Visiting statement:
> _3 = _9 %[fl] _11;
> Found new range for _3: [0, +INF]
>
> which is plain wrong since the sign of FLOOR_MOD_EXPR is the sign of the
> divisor and not that of the dividend (the latter is for TRUNC_MOD_EXPR).
>
> I have attached a fix for mainline and another one for the 4.9/5 branches.
>
> Tested on x86_64-suse-linux, OK for all active branches?
>
>
> 2015-10-20  Eric Botcazou  <ebotcazou@adacore.com>
>
> 	* fold-const.c (tree_binary_nonnegative_warnv_p) <FLOOR_MOD_EXPR>:
> 	Recurse on operand #1 instead of operand #0.
> 	<CEIL_MOD_EXPR>: Do not recurse.
> 	<ROUND_MOD_EXPR>: Likewise.
Isn't this a function of the language and in some cases isn't it 
implementation defined (true for C/C++ until C++11)?

Even with that in mind, I think FLOOR_MOD_EXPR and TRUNC_MOD_EXPR are 
more correct with your patch.  I'm just not sure about CEIL & ROUND.

Jeff