Richard Biener <[email protected]> writes:
>> Am 20.07.2023 um 18:59 schrieb Richard Sandiford <[email protected]>:
>>
>> Richard Biener <[email protected]> writes:
>>>>> Am 20.07.2023 um 16:09 schrieb Richard Sandiford
>>>>> <[email protected]>:
>>>>
>>>> Richard Biener via Gcc-patches <[email protected]> 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.
>
> Hmm, but I arrived here with that not being the case … (the chosen Lay-out
> not zero)
By chosen layout for the partition, I meant:
unsigned int from_layout_i = m_partitions[partition_i].layout;
That should be 0 for these external vector nodes due to the
start_choosing_layout code that you mentioned in the PR. to_layout_i
(the layout that the caller wants for a use of the node) can be anything,
so yeah, to_layout_i != 0 has to go through the "else" arm and generate
a VEC_PERM_EXPR. But because from_layout_i == 0 for these nodes,
the "else" arm should handle all cases correctly, not just the
to_layout_i != 0 case.
Thanks,
Richard
