Re: [PATCH] Fix UBSAN errors in ipa-cp.

[Jan Hubicka <hubicka@ucw.cz>]

> I see the following UBSAN errors:
> 
> ./xgcc -B. /home/marxin/Programming/gcc/gcc/testsuite/g++.dg/ipa/pr96806.C -std=c++11 -O -fipa-cp -fipa-cp-clone --param=ipa-cp-max-recursive-depth=94 --param=logical-op-non-short-circuit=0
> /home/marxin/Programming/gcc2/gcc/ipa-cp.c:3866:20: runtime error: signed integer overflow: 64 + 2147483584 cannot be represented in type 'int'
> /home/marxin/Programming/gcc2/gcc/ipa-cp.c:3843:16: runtime error: signed integer overflow: -2147483648 + -2147483648 cannot be represented in type 'int'
> /home/marxin/Programming/gcc2/gcc/ipa-cp.c:3864:20: runtime error: signed integer overflow: 1 + 2147483647 cannot be represented in type 'int'
> 
> Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
> 
> Ready to be installed?
> Thanks,
> Martin
> 
> gcc/ChangeLog:
> 
> 	* ipa-cp.c (safe_add): Handle also very small negative values.
> 	(value_topo_info::propagate_effects): Use properly safe_add.

Perhaps it is time to turn the profile count scaled valued to sreals
like we do in inline heuristics and other places?

Honza
> ---
>  gcc/ipa-cp.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/gcc/ipa-cp.c b/gcc/ipa-cp.c
> index b3e7d41ea10..e39ee28726d 100644
> --- a/gcc/ipa-cp.c
> +++ b/gcc/ipa-cp.c
> @@ -3832,13 +3832,15 @@ propagate_constants_topo (class ipa_topo_info *topo)
>  /* Return the sum of A and B if none of them is bigger than INT_MAX/2, return
> -   the bigger one if otherwise.  */
> +   the bigger one if otherwise.  Similarly for negative numbers.  */
>  static int
>  safe_add (int a, int b)
>  {
>    if (a > INT_MAX/2 || b > INT_MAX/2)
>      return a > b ? a : b;
> +  else if (a < -INT_MAX/2 || b < -INT_MAX/2)
> +    return a > b ? b : a;
>    else
>      return a + b;
>  }
> @@ -3861,9 +3863,10 @@ value_topo_info<valtype>::propagate_effects ()
>        for (val = base; val; val = val->scc_next)
>  	{
> -	  time = safe_add (time,
> -			   val->local_time_benefit + val->prop_time_benefit);
> -	  size = safe_add (size, val->local_size_cost + val->prop_size_cost);
> +	  time = safe_add (time, val->local_time_benefit);
> +	  time = safe_add (time, val->prop_time_benefit);
> +	  size = safe_add (size, val->local_size_cost);
> +	  size = safe_add (size, val->prop_size_cost);
>  	}
>        for (val = base; val; val = val->scc_next)
> -- 
> 2.28.0
>