[Bug tree-optimization/51254] Missed Optimization: IVOPTS don't handle unaligned memory access.

["rguenther at suse dot de" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51254

--- Comment #4 from rguenther at suse dot de <rguenther at suse dot de> 2011-12-13 10:27:48 UTC ---
On Tue, 13 Dec 2011, duyuehai at gmail dot com wrote:

> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51254
> 
> Yuehai Du <duyuehai at gmail dot com> changed:
> 
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>                  CC|                            |duyuehai at gmail dot com,
>                    |                            |rguenth at gcc dot gnu.org
> 
> --- Comment #2 from Yuehai Du <duyuehai at gmail dot com> 2011-12-13 04:15:12 UTC ---
> Hi Richard
>   would it be ok if i submit a patch like this to fix this bug:
> 
> Index: gcc/tree-ssa-loop-ivopts.c
> ===================================================================
> --- gcc/tree-ssa-loop-ivopts.c    (çæ 182270)
> +++ gcc/tree-ssa-loop-ivopts.c    (åäåæ)
> @@ -102,6 +102,7 @@ along with GCC; see the file COPYING3.  If not see
>     cost of different addressing modes.  This should be moved to a TBD
>     interface between the GIMPLE and RTL worlds.  */
>  #include "expr.h"
> +#include "optabs.h"
> 
>  /* The infinite cost.  */
>  #define INFTY 10000000
> @@ -1771,6 +1772,7 @@ find_interesting_uses_address (struct ivopts_data
>      }
>    else
>      {
> +      enum machine_mode mem_mode;
>        ifs_ivopts_data.ivopts_data = data;
>        ifs_ivopts_data.stmt = stmt;
>        ifs_ivopts_data.step = size_zero_node;
> @@ -1786,7 +1788,9 @@ find_interesting_uses_address (struct ivopts_data
> 
>        /* Moreover, on strict alignment platforms, check that it is
>       sufficiently aligned.  */
> -      if (STRICT_ALIGNMENT && may_be_unaligned_p (base, step))
> +      mem_mode = TYPE_MODE (TREE_TYPE (*op_p));
> +      if (STRICT_ALIGNMENT && may_be_unaligned_p (base, step)
> +          && optab_handler (movmisalign_optab, mem_mode) == CODE_FOR_nothing)
>      goto fail;
> 
>        base = build_fold_addr_expr (base);

This won't fix it - the movmisalign optab will not be used at expansion
time as IVOPTs does not properly transfer the misalignment to the
access type.

Richard.