[PATCH] Fix PR tree-optimization/77550
Bernd Edlinger
bernd.edlinger@hotmail.de
Mon Sep 19 16:20:00 GMT 2016
On 09/19/16 11:25, Richard Biener wrote:
> On Sun, 18 Sep 2016, Bernd Edlinger wrote:
>
>> Hi,
>>
>> this PR shows that in vectorizable_store and vectorizable_load
>> as well, the vector access always uses the first dr as the alias
>> type for the whole access. But that is not right, if they are
>> different types, like in this example.
>>
>> So I tried to replace all reference_alias_ptr_type (DR_REF (first_dr))
>> by an alias type that is correct for all references in the whole
>> access group. With this patch we fall back to ptr_type_node, which
>> can alias anything, if the group consists of different alias sets.
>>
>>
>> Bootstrapped and reg-tested on x86_64-pc-linux-gnu.
>> Is it OK for trunk and gcc-6-branch?
>
> +/* Function get_group_alias_ptr_type.
> +
> + Return the alias type for the group starting at FIRST_STMT
> + containing GROUP_SIZE elements. */
> +
> +static tree
> +get_group_alias_ptr_type (gimple *first_stmt, int group_size)
> +{
> + struct data_reference *first_dr, *next_dr;
> + gimple *next_stmt;
> + int i;
> +
> + first_dr = STMT_VINFO_DATA_REF (vinfo_for_stmt (first_stmt));
> + next_stmt = GROUP_NEXT_ELEMENT (vinfo_for_stmt (first_stmt));
> + for (i = 1; i < group_size && next_stmt; i++)
> + {
>
>
> there is no need to pass in group_size, it's enough to walk
> GROUP_NEXT_ELEMENT until it becomes NULL.
>
> Ok with removing the redundant arg.
>
> Thanks,
> Richard.
>
Hmmm, I'm afraid this needs one more iteration.
I tried first to check if there are no stmts after the group_size
and noticed there are cases when group_size is 0,
for instance in gcc.dg/torture/pr36244.c.
I think there is a bug in vectorizable_load, here:
if (grouped_load)
{
first_stmt = GROUP_FIRST_ELEMENT (stmt_info);
/* For SLP vectorization we directly vectorize a subchain
without permutation. */
if (slp && ! SLP_TREE_LOAD_PERMUTATION (slp_node).exists ())
first_stmt = ;
group_size = GROUP_SIZE (vinfo_for_stmt (first_stmt));
= 0, and even worse:
group_gap_adj = vf * group_size - nunits * vec_num;
= -4 !
apparently GROUP_SIZE is only valid on the GROUP_FIRST_ELEMENT,
while it may be 0 on SLP_TREE_SCALAR_STMTS (slp_node)[0]
moving the GROUP_SIZE up before first_stmt is overwritten
results in no different code....
Bernd.
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