[PATCH] array-bounds, v2: Fix up ICE on overaligned variables [PR99109]

[Richard Biener]

On Thu, 18 Feb 2021, Jakub Jelinek wrote:

> On Wed, Feb 17, 2021 at 02:38:04PM -0700, Martin Sebor via Gcc-patches wrote:
> > How does build_printable_array_type sound?
> 
> This adjusted version also works and has been successfully
> bootstrapped/regtested on x86_64-linux and i686-linux.
> 
> Ok for trunk?

OK.

Richard.

> 2021-02-18  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR middle-end/99109
> 	* gimple-array-bounds.cc (build_zero_elt_array_type): Rename to ...
> 	(build_printable_array_type): ... this.  Add nelts argument.  For
> 	overaligned eltype, use TYPE_MAIN_VARIANT (eltype) instead.  If
> 	nelts, call build_array_type_nelts.
> 	(array_bounds_checker::check_mem_ref): Use build_printable_array_type
> 	instead of build_zero_elt_array_type and build_array_type_nelts.
> 
> 	* g++.dg/warn/Warray-bounds-17.C: New test.
> 
> --- gcc/gimple-array-bounds.cc.jj	2021-01-04 10:25:37.471249246 +0100
> +++ gcc/gimple-array-bounds.cc	2021-02-17 23:30:34.168721374 +0100
> @@ -372,12 +372,23 @@ array_bounds_checker::check_array_ref (l
>    return warned;
>  }
>  
> -/* Hack around the internal representation constraints and build a zero
> -   element array type that actually renders as T[0] in diagnostcs.  */
> +/* Wrapper around build_array_type_nelts that makes sure the array
> +   can be created at all and handles zero sized arrays specially.  */
>  
>  static tree
> -build_zero_elt_array_type (tree eltype)
> +build_printable_array_type (tree eltype, unsigned HOST_WIDE_INT nelts)
>  {
> +  if (TYPE_SIZE_UNIT (eltype)
> +      && TREE_CODE (TYPE_SIZE_UNIT (eltype)) == INTEGER_CST
> +      && !integer_zerop (TYPE_SIZE_UNIT (eltype))
> +      && TYPE_ALIGN_UNIT (eltype) > 1
> +      && wi::zext (wi::to_wide (TYPE_SIZE_UNIT (eltype)),
> +		   ffs_hwi (TYPE_ALIGN_UNIT (eltype)) - 1) != 0)
> +    eltype = TYPE_MAIN_VARIANT (eltype);
> +
> +  if (nelts)
> +    return build_array_type_nelts (eltype, nelts);
> +
>    tree idxtype = build_range_type (sizetype, size_zero_node, NULL_TREE);
>    tree arrtype = build_array_type (eltype, idxtype);
>    arrtype = build_distinct_type_copy (TYPE_MAIN_VARIANT (arrtype));
> @@ -561,10 +572,7 @@ array_bounds_checker::check_mem_ref (loc
>  	return false;
>  
>        offset_int nelts = arrbounds[1] / eltsize;
> -      if (nelts == 0)
> -	reftype = build_zero_elt_array_type (reftype);
> -      else
> -	reftype = build_array_type_nelts (reftype, nelts.to_uhwi ());
> +      reftype = build_printable_array_type (reftype, nelts.to_uhwi ());
>      }
>    else if (TREE_CODE (arg) == ADDR_EXPR)
>      {
> @@ -675,7 +683,7 @@ array_bounds_checker::check_mem_ref (loc
>        /* Treat a reference to a non-array object as one to an array
>  	 of a single element.  */
>        if (TREE_CODE (reftype) != ARRAY_TYPE)
> -	reftype = build_array_type_nelts (reftype, 1);
> +	reftype = build_printable_array_type (reftype, 1);
>  
>        /* Extract the element type out of MEM_REF and use its size
>  	 to compute the index to print in the diagnostic; arrays
> --- gcc/testsuite/g++.dg/warn/Warray-bounds-17.C.jj	2021-02-16 17:24:14.178813304 +0100
> +++ gcc/testsuite/g++.dg/warn/Warray-bounds-17.C	2021-02-16 17:23:35.305251062 +0100
> @@ -0,0 +1,15 @@
> +// PR middle-end/99109
> +// { dg-do compile }
> +// { dg-options "-O2 -Warray-bounds" }
> +
> +typedef int A __attribute__((aligned (64)));
> +void foo (int *);
> +
> +void
> +bar (void)
> +{
> +  A b;			// { dg-message "while referencing" }
> +  int *p = &b;
> +  int *x = (p - 1);	// { dg-warning "outside array bounds" }
> +  foo (x);
> +}
> 
> 
> 	Jakub
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)