[PATCH, PR 42398] More generic type compatibility checking in sra_modify_expr

[Richard Guenther]

On Tue, Dec 22, 2009 at 9:48 PM, Martin Jambor <mjambor@suse.cz> wrote:
> Hi,
>
> the testcase in PR 42398 persuaded me that we need fully generic type
> compatibility checking in sra_modify_expr rather than looking for
> potential causes of incompatibilities in situations that are handled
> by the function.  The downside is that the type conversion code leaves
> the old aggregate around (it has to for TREE_ADDRESSABLE types) and we
> will not be drawn to new causes of it being used by the assert if any
> occur.
>
> The alternative would be to add code generating new temporaries and
> then an assignment from a VIEW_CONVERT_EXPRs but that hardly seems
> worth it for assembly statements.
>
> The patch leaves flag grp_different_types useless and so I removed it
> so that it is not calculated needlessly.
>
> I have successfully bootstrapped and regression tested the patch on
> x86_64-linux.  OK for trunk?

Ok.

Thanks,
Richard.

> Thanks,
>
> Martin
>
> 2009-12-22  Martin Jambor  <mjambor@suse.cz>
>
>        PR tree-optimization/42398
>        * tree-sra.c (struct access): Removed flag grp_different_types.
>        (dump_access): Do not dump the removed flag.
>        (sort_and_splice_var_accesses): Do not set the removed flag.
>        (sra_modify_expr): Check for type compatibility directly.
>
>        * testsuite/gcc.c-torture/compile/pr42398.c: New test.
>
>
> Index: mine/gcc/tree-sra.c
> ===================================================================
> --- mine.orig/gcc/tree-sra.c
> +++ mine/gcc/tree-sra.c
> @@ -199,10 +199,6 @@ struct access
>      BIT_FIELD_REF?  */
>   unsigned grp_partial_lhs : 1;
>
> -  /* Does this group contain accesses to different types? (I.e. through a union
> -     or a similar mechanism).  */
> -  unsigned grp_different_types : 1;
> -
>   /* Set when a scalar replacement should be created for this variable.  We do
>      the decision and creation at different places because create_tmp_var
>      cannot be called from within FOR_EACH_REFERENCED_VAR. */
> @@ -343,14 +339,12 @@ dump_access (FILE *f, struct access *acc
>     fprintf (f, ", grp_write = %d, grp_read = %d, grp_hint = %d, "
>             "grp_covered = %d, grp_unscalarizable_region = %d, "
>             "grp_unscalarized_data = %d, grp_partial_lhs = %d, "
> -            "grp_different_types = %d, grp_to_be_replaced = %d, "
> -            "grp_maybe_modified = %d, "
> +            "grp_to_be_replaced = %d, grp_maybe_modified = %d, "
>             "grp_not_necessarilly_dereferenced = %d\n",
>             access->grp_write, access->grp_read, access->grp_hint,
>             access->grp_covered, access->grp_unscalarizable_region,
>             access->grp_unscalarized_data, access->grp_partial_lhs,
> -            access->grp_different_types, access->grp_to_be_replaced,
> -            access->grp_maybe_modified,
> +            access->grp_to_be_replaced, access->grp_maybe_modified,
>             access->grp_not_necessarilly_dereferenced);
>   else
>     fprintf (f, ", write = %d, grp_partial_lhs = %d\n", access->write,
> @@ -1434,7 +1428,6 @@ sort_and_splice_var_accesses (tree var)
>       bool grp_read = !access->write;
>       bool multiple_reads = false;
>       bool grp_partial_lhs = access->grp_partial_lhs;
> -      bool grp_different_types = false;
>       bool first_scalar = is_gimple_reg_type (access->type);
>       bool unscalarizable_region = access->grp_unscalarizable_region;
>
> @@ -1466,7 +1459,6 @@ sort_and_splice_var_accesses (tree var)
>                grp_read = true;
>            }
>          grp_partial_lhs |= ac2->grp_partial_lhs;
> -         grp_different_types |= !types_compatible_p (access->type, ac2->type);
>          unscalarizable_region |= ac2->grp_unscalarizable_region;
>          relink_to_new_repr (access, ac2);
>
> @@ -1485,7 +1477,6 @@ sort_and_splice_var_accesses (tree var)
>       access->grp_read = grp_read;
>       access->grp_hint = multiple_reads;
>       access->grp_partial_lhs = grp_partial_lhs;
> -      access->grp_different_types = grp_different_types;
>       access->grp_unscalarizable_region = unscalarizable_region;
>       if (access->first_link)
>        add_access_to_work_queue (access);
> @@ -2136,11 +2127,9 @@ sra_modify_expr (tree *expr, gimple_stmt
>
>          We also want to use this when accessing a complex or vector which can
>          be accessed as a different type too, potentially creating a need for
> -         type conversion  (see PR42196).  */
> -      if (!is_gimple_reg_type (type)
> -         || (access->grp_different_types
> -             && (TREE_CODE (type) == COMPLEX_TYPE
> -                 || TREE_CODE (type) == VECTOR_TYPE)))
> +         type conversion (see PR42196) and when scalarized unions are involved
> +         in assembler statements (see PR42398).  */
> +      if (!useless_type_conversion_p (type, access->type))
>        {
>          tree ref = access->base;
>          bool ok;
> @@ -2171,10 +2160,7 @@ sra_modify_expr (tree *expr, gimple_stmt
>            }
>        }
>       else
> -       {
> -         gcc_assert (useless_type_conversion_p (type, access->type));
> -         *expr = repl;
> -       }
> +       *expr = repl;
>       sra_stats.exprs++;
>     }
>
> Index: mine/gcc/testsuite/gcc.c-torture/compile/pr42398.c
> ===================================================================
> --- /dev/null
> +++ mine/gcc/testsuite/gcc.c-torture/compile/pr42398.c
> @@ -0,0 +1,6 @@
> +int ptrace_setregs(void)
> +{
> +  union { unsigned int l; int t; } __gu_tmp;
> +  __asm__ __volatile__("" : "=r" (__gu_tmp.l));
> +  return __gu_tmp.t;
> +}
>
>