Re: [PATCH] gimple-ssa-warn-access: Cast huge params to sizetype before using them in maybe_check_access_sizes [PR113410]

[Richard Biener <rguenther@suse.de>]

On Wed, 17 Jan 2024, Jakub Jelinek wrote:

> Hi!
> 
> WHen a VLA is created with some very high precision size expression
> (say __int128, or _BitInt(65535) etc.), we cast it to sizetype, because
> we can't have arrays longer than what can be expressed in sizetype.
> 
> But the maybe_check_access_sizes code when trying to determine ranges
> wasn't doing this but was using fixed buffers for the sizes.  While
> __int128 could still be handled (fit into the buffers), obviously
> arbitrary _BitInt parameter ranges can't, they can be in the range of
> up to almost 20KB per number.  It doesn't make sense to print such
> ranges though, no array can be larger than sizetype precision, and
> ranger's range_of_expr can handle NOP_EXPRs/CONVERT_EXPRs wrapping a
> PARM_DECL just fine, so the following patch just casts the excessively
> large counters for the range determination purposes to sizetype.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

OK

> 2024-01-17  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR middle-end/113410
> 	* gimple-ssa-warn-access.cc (pass_waccess::maybe_check_access_sizes):
> 	If access_nelts is integral with larger precision than sizetype,
> 	fold_convert it to sizetype.
> 
> 	* gcc.dg/bitint-72.c: New test.
> 
> --- gcc/gimple-ssa-warn-access.cc.jj	2024-01-03 11:51:30.087751231 +0100
> +++ gcc/gimple-ssa-warn-access.cc	2024-01-16 19:25:35.408958088 +0100
> @@ -3406,6 +3406,15 @@ pass_waccess::maybe_check_access_sizes (
>        else
>  	access_nelts = rwm->get (sizidx)->size;
>  
> +      /* If access_nelts is e.g. a PARM_DECL with larger precision than
> +	 sizetype, such as __int128 or _BitInt(34123) parameters,
> +	 cast it to sizetype.  */
> +      if (access_nelts
> +	  && INTEGRAL_TYPE_P (TREE_TYPE (access_nelts))
> +	  && (TYPE_PRECISION (TREE_TYPE (access_nelts))
> +	      > TYPE_PRECISION (sizetype)))
> +	access_nelts = fold_convert (sizetype, access_nelts);
> +
>        /* Format the value or range to avoid an explosion of messages.  */
>        char sizstr[80];
>        tree sizrng[2] = { size_zero_node, build_all_ones_cst (sizetype) };
> --- gcc/testsuite/gcc.dg/bitint-72.c.jj	2024-01-16 19:31:33.839938120 +0100
> +++ gcc/testsuite/gcc.dg/bitint-72.c	2024-01-16 19:31:06.000328741 +0100
> @@ -0,0 +1,16 @@
> +/* PR middle-end/113410 */
> +/* { dg-do compile { target bitint } } */
> +/* { dg-options "-std=c23" } */
> +
> +#if __BITINT_MAXWIDTH__ >= 905
> +void bar (_BitInt(905) n, int[n]);
> +#else
> +void bar (int n, int[n]);
> +#endif
> +
> +void
> +foo (int n)
> +{
> +  int buf[n];
> +  bar (n, buf);
> +}
> 
> 	Jakub
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)