Hi Richard,
Thanks very much for reviewing my patch. I'll update it as your comments.
Before sending the next version, I've several questions embedded for further
check.
on 2019/7/2 下午8:43, Richard Biener wrote:
> On Wed, 20 Mar 2019, Kewen.Lin wrote:
>
>> +/* { dg-require-effective-target vect_double } */
>> +/* { dg-require-effective-target powerpc_vsx_ok { target { powerpc*-*-* } }
>> } */
>> +/* { dg-options "-O2 -ffast-math" } */
>> +/* { dg-options "-O2 -ffast-math -mvsx -fdump-tree-reassoc1" { target {
>> powerpc*-*-* } } } */
>
> Use
>
> /* { dg-additional-options "-mvsx" { target { powerpc...
>
> that saves duplicate typing. I guess that x86_64/i?86 also works
> if you enable SSE2 - can you check that and do adjustments accordingly?
>
OK, I'll learn SSE2 and update it.
>> +/* Hold the information of one specific VECTOR_TYPE SSA_NAME.
>> + - offsets: for different BIT_FIELD_REF offsets accessing same VECTOR.
>> + - ops_indexes: the index of vec ops* for each relavant BIT_FIELD_REF.
>> */
>> +struct v_info
>> +{
>> + auto_vec<unsigned HOST_WIDE_INT, 32> offsets;
>
> with SVE this probably needs to be poly_int64 or so
>
OK, will extend it to poly_int64 (can it be negative? or poly_uint64 better?)
>> + auto_vec<unsigned, 32> ops_indexes;
>> +};
>
> To have less allocations you could use a
>
> auto_vec<std::pair<unsigned HOST_WIDE_INT, unsigned>, 32> elements;
>
> or even
>
> hash_map<tree, vec<std::pair<unsigned HOST_WIDE_INT, unsigned> > >
>
> where you use .release() in the cleanup and .create (TYPE_VECTOR_SUBPARTS
> (vector_type)) during collecting and then can use quick_push ()
> (ah, no - duplicates...).
>
Good idea!
>> +
>> +typedef struct v_info *v_info_ptr;
>> +
>> +/* Comparison function for qsort on unsigned BIT_FIELD_REF offsets. */
>> +static int
>> +unsigned_cmp (const void *p_i, const void *p_j)
>> +{
>> + if (*(const unsigned HOST_WIDE_INT *) p_i
>> + >= *(const unsigned HOST_WIDE_INT *) p_j)
>> + return 1;
>> + else
>> + return -1;
>
> That's an issue with some qsort implementations comparing
> an element against itself.
>
> I think so you should add the equality case.
>
The equality case seems already involved in ">=".
Do you mean that I need to make it equality case explicitly?
Or return zero for "=="? like:
const unsigned HOST_WIDE_INT val_i = *(const unsigned HOST_WIDE_INT *) p_i;
const unsigned HOST_WIDE_INT val_j = *(const unsigned HOST_WIDE_INT *) p_j;
if (val_i != val_j)
return val_i > val_j? 1: -1;
else
return 0;
>> +
>> + TODO:
>> + 1) The current implementation restrict all candidate VECTORs should have
>> + the same VECTOR type, but it can be extended into different groups by
>> + VECTOR types in future if any profitable cases found.
>> + 2) The current implementation requires the whole VECTORs should be fully
>> + covered, but it can be extended to support partial, checking adjacent
>> + but not fill the whole, it may need some cost model to define the
>> + boundary to do or not.
>> +
>> + tree elem_type = TREE_TYPE (vec_type);
>> + unsigned HOST_WIDE_INT size = TREE_INT_CST_LOW (TYPE_SIZE
>> (elem_type));
>> + if (size != TREE_INT_CST_LOW (op1))
>
> if (!tree_int_cst_equal (TYPE_SIZE (elem_type), op1))
>
> avoids some of the TREE_INT_CST_LOW we like to avoid.
>
> You miss a check for op2 % op1 being zero. Given you store a
> HOST_WIDE_INT offset you also want to check for INTEGER_CST op1/op2
> (beware of SVE...).
OK, thanks! For op2 % op1 == zero, I thought it's a must for granted, I'll fix
it.
I think it can be constructed in IR artificially, but since I have almost none
knowledge
on other targets vector support, I'm curious that does it exist in real world
codes?
btw, BIT_FIELD_REF in tree.def says the op1/op2 is constant, it looks need to
be updated
due to SVE?
>
> There's also a poly-int friendly multiple_p predicate so you could
> have the initial checks SVE friendly but bail out on non-INTEGER_CST
> offset later.
>
Got it, thanks!
>
> Since you are using a hashtable keyed off SSA name pointers code
> generation will depend on host addresses here if you consider
> there's one mismatching vector type that might become ref_vec
> dependent on the order of elements in the hashtable. That's
> a no-no.
>
> Even if doing it like above looks to possibly save compile-time
> by avoiding qsort calls I think the appropriate thing to do is
> to partition the vector candidates into sets of compatible
> vectors (consider summing two v2df and two v4df vectors for example)
> and then take out ones you disqualify because they do not cover
> the vector in full.
>
You are absolutely right, the randomness of hashtable keys order could
be a problem here. The partition part is TODO 1). Since Power has only
one kind whole vector width now, doesn't have v2df and v4df co-existence,
it's put into TODO. I will extend it in the next version of patch, add
one more hashtable from vector type mode to v_info_map, feel free to
correct me if you have any concerns.
> I think whether the vector is fully covered can be done way cheaper
> as well by using a sbitmap and clearing a bit whenever its
> corresponding lane is in the vector (and bailing out if the bit
> was already clear since you then got a duplicate). So start
> with bitmap_ones () and at the end check bitmap_empty_p ().
> I don't think you depend on the vector being sorted later?
>
Good idea, yes, it doesn't depend on sorted or not.
>> + {
>> + sum = build_and_add_sum (TREE_TYPE (ref_vec), sum_vec, tr, opcode);
>> + info = *(v_info_map.get (tr));
>> + unsigned j;
>> + FOR_EACH_VEC_ELT (info->ops_indexes, j, idx)
>> + {
>> + gimple *def = SSA_NAME_DEF_STMT ((*ops)[idx]->op);
>> + gimple_set_visited (def, true);
>
> you set the visited flag to get the ops definition DCEd eventually, right?
> Note this in a comment.
>
Yes, it's for that. Will add the comment, thanks!
