Re: [PATCH] Improve build_simple_mem_ref_loc (PR middle-end/83185)

[Richard Biener <rguenther@suse.de>]

On Wed, 29 Nov 2017, Jakub Jelinek wrote:

> Hi!
> 
> This PR is about forwprop propagating:
>   _17 = __builtin_alloca_with_align (_16, 256);
>   _18 = _17 + 32;
>   __builtin___asan_alloca_poison (_18, _8);
>   _7 = &*_18[4];
>   __builtin_va_start (_7, 0);
> to:
>   _17 = __builtin_alloca_with_align (_16, 256);
>   _18 = _17 + 32;
>   __builtin___asan_alloca_poison (_18, _8);
>   _7 = &MEM[(struct [0:D.2257][1] *)_17 + 32B][4];
>   __builtin_va_start (_7, 0);
> which is something the verifiers allow and then backend VA_START
> handling calling build_simple_mem_ref_loc on the ADDR_EXPR it got.
> get_addr_base_and_unit_offset only looks through a MEM_REF if it
> has ADDR_EXPR as the first operand, which is not the case here, so nothing
> sums up the 96 offset from the [4] ARRAY_REF with the extra 32 from the
> MEM_REF.
> 
> Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
> trunk?

Ok.

Richard.

> 2017-11-29  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR middle-end/83185
> 	* tree.c (build_simple_mem_ref_loc): Handle
> 	get_addr_base_and_unit_offset returning a MEM_REF.
> 
> 	* gcc.dg/asan/pr83185.c: New test.
> 
> --- gcc/tree.c.jj	2017-11-28 12:11:38.000000000 +0100
> +++ gcc/tree.c	2017-11-28 17:22:01.800939050 +0100
> @@ -4692,7 +4692,13 @@ build_simple_mem_ref_loc (location_t loc
>      {
>        ptr = get_addr_base_and_unit_offset (TREE_OPERAND (ptr, 0), &offset);
>        gcc_assert (ptr);
> -      ptr = build_fold_addr_expr (ptr);
> +      if (TREE_CODE (ptr) == MEM_REF)
> +	{
> +	  offset += mem_ref_offset (ptr).to_short_addr ();
> +	  ptr = TREE_OPERAND (ptr, 0);
> +	}
> +      else
> +	ptr = build_fold_addr_expr (ptr);
>        gcc_assert (is_gimple_reg (ptr) || is_gimple_min_invariant (ptr));
>      }
>    tem = build2 (MEM_REF, TREE_TYPE (ptype),
> --- gcc/testsuite/gcc.dg/asan/pr83185.c.jj	2017-11-28 17:24:15.540329283 +0100
> +++ gcc/testsuite/gcc.dg/asan/pr83185.c	2017-11-28 17:24:19.851277394 +0100
> @@ -0,0 +1,14 @@
> +/* PR middle-end/83185 */
> +/* { dg-do compile } */
> +
> +#include <stdarg.h>
> +
> +int bar (void);
> +
> +void
> +foo (int i, ...)
> +{
> +  va_list aps[bar()];
> +  va_start (aps[4], i);
> +  va_end (aps[4]);
> +}
> 
> 	Jakub
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)