Richard Biener <rguent...@suse.de> writes:
>> Am 20.07.2023 um 16:09 schrieb Richard Sandiford <richard.sandif...@arm.com>:
>>
>> Richard Biener via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
>>> When we materialize a layout we push edge permutes to constant/external
>>> defs without checking we can actually do so. For externals defined
>>> by vector stmts rather than scalar components we can't.
>>>
>>> Bootstrapped and tested on x86_64-unknown-linux-gnu.
>>>
>>> OK?
>>>
>>> Thanks,
>>> Richard.
>>>
>>> PR tree-optimization/110742
>>> * tree-vect-slp.cc (vect_optimize_slp_pass::get_result_with_layout):
>>> Do not materialize an edge permutation in an external node with
>>> vector defs.
>>> (vect_slp_analyze_node_operations_1): Guard purely internal
>>> nodes better.
>>>
>>> * g++.dg/torture/pr110742.C: New testcase.
>>> ---
>>> gcc/testsuite/g++.dg/torture/pr110742.C | 47 +++++++++++++++++++++++++
>>> gcc/tree-vect-slp.cc | 8 +++--
>>> 2 files changed, 53 insertions(+), 2 deletions(-)
>>> create mode 100644 gcc/testsuite/g++.dg/torture/pr110742.C
>>>
>>> diff --git a/gcc/testsuite/g++.dg/torture/pr110742.C
>>> b/gcc/testsuite/g++.dg/torture/pr110742.C
>>> new file mode 100644
>>> index 00000000000..d41ac0479d2
>>> --- /dev/null
>>> +++ b/gcc/testsuite/g++.dg/torture/pr110742.C
>>> @@ -0,0 +1,47 @@
>>> +// { dg-do compile }
>>> +
>>> +struct HARD_REG_SET {
>>> + HARD_REG_SET operator~() const {
>>> + HARD_REG_SET res;
>>> + for (unsigned int i = 0; i < (sizeof(elts) / sizeof((elts)[0])); ++i)
>>> + res.elts[i] = ~elts[i];
>>> + return res;
>>> + }
>>> + HARD_REG_SET operator&(const HARD_REG_SET &other) const {
>>> + HARD_REG_SET res;
>>> + for (unsigned int i = 0; i < (sizeof(elts) / sizeof((elts)[0])); ++i)
>>> + res.elts[i] = elts[i] & other.elts[i];
>>> + return res;
>>> + }
>>> + unsigned long elts[4];
>>> +};
>>> +typedef const HARD_REG_SET &const_hard_reg_set;
>>> +inline bool hard_reg_set_subset_p(const_hard_reg_set x, const_hard_reg_set
>>> y) {
>>> + unsigned long bad = 0;
>>> + for (unsigned int i = 0; i < (sizeof(x.elts) / sizeof((x.elts)[0])); ++i)
>>> + bad |= (x.elts[i] & ~y.elts[i]);
>>> + return bad == 0;
>>> +}
>>> +inline bool hard_reg_set_empty_p(const_hard_reg_set x) {
>>> + unsigned long bad = 0;
>>> + for (unsigned int i = 0; i < (sizeof(x.elts) / sizeof((x.elts)[0])); ++i)
>>> + bad |= x.elts[i];
>>> + return bad == 0;
>>> +}
>>> +extern HARD_REG_SET rr[2];
>>> +extern int t[2];
>>> +extern HARD_REG_SET nn;
>>> +static HARD_REG_SET mm;
>>> +void setup_reg_class_relations(void) {
>>> + HARD_REG_SET intersection_set, union_set, temp_set2;
>>> + for (int cl2 = 0; cl2 < 2; cl2++) {
>>> + temp_set2 = rr[cl2] & ~nn;
>>> + if (hard_reg_set_empty_p(mm) && hard_reg_set_empty_p(temp_set2)) {
>>> + mm = rr[0] & nn;
>>> + if (hard_reg_set_subset_p(mm, intersection_set))
>>> + if (!hard_reg_set_subset_p(mm, temp_set2) ||
>>> + hard_reg_set_subset_p(rr[0], rr[t[cl2]]))
>>> + t[cl2] = 0;
>>> + }
>>> + }
>>> +}
>>> diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
>>> index 693621ca990..1d79c77e8ce 100644
>>> --- a/gcc/tree-vect-slp.cc
>>> +++ b/gcc/tree-vect-slp.cc
>>> @@ -5198,7 +5198,10 @@ vect_optimize_slp_pass::get_result_with_layout
>>> (slp_tree node,
>>> return result;
>>>
>>> if (SLP_TREE_DEF_TYPE (node) == vect_constant_def
>>> - || SLP_TREE_DEF_TYPE (node) == vect_external_def)
>>> + || (SLP_TREE_DEF_TYPE (node) == vect_external_def
>>> + && (to_layout_i == 0
>>> + /* We can't permute vector defs. */
>>> + || SLP_TREE_VEC_DEFS (node).is_empty ())))
>>
>> Guess it's personal preference, but IMO it's easier to follow without the
>> to_layout_i condition, so that it ties directly to the create_partitions
>> test.
>
> I don’t understand- in the code guarding this we seem to expect to_layout_i
> == 0 and that’s the case we can handle as noop. I didn’t understand why the
> function doesn’t always just do nothing in this case though, so I must have
> missed something.
OK, so I guess that disproves that my way is easier to understand :)
I think logically, the code is doing the equivalent of:
int partition_i = m_vertices[node->vertex].partition;
if (partition < 0)
{
/* If the vector is uniform or unchanged, there's nothing to do. */
...
}
else
{
... Return node if to_layout_i matches this partition's chosen layout...
}
And I guess I should have written it that way.
So when there is no partition, we have a constant or external def
built from individual scalars. We can use the node as-is if the
caller wants an unpermuted node or if all elements are equal
(so that the permutation doesn't matter). Otherwise we need
to permute the scalars.
When there is a partition, we can use the node as-is if the caller
wants the layout that was chosen for that partition. Otherwise we
need a new VEC_PERM_EXPR node.
In the particular case of external defs built from vectors, we're
guaranteed that the node's chosen layout is 0 (i.e. the original layout),
and so both ways work. But in principle this case fits the "else" arm
better than the "then" arm, because we're dealing with a node that is in
a partition, and that is not built from scalars.
Thanks,
Richard
