Prathamesh Kulkarni <prathamesh.kulka...@linaro.org> writes:
> On Tue, 3 May 2022 at 18:25, Richard Sandiford
> <richard.sandif...@arm.com> wrote:
>>
>> Prathamesh Kulkarni <prathamesh.kulka...@linaro.org> writes:
>> > On Tue, 4 Jan 2022 at 19:12, Richard Sandiford
>> > <richard.sandif...@arm.com> wrote:
>> >>
>> >> Richard Biener <rguent...@suse.de> writes:
>> >> > On Tue, 4 Jan 2022, Richard Sandiford wrote:
>> >> >
>> >> >> Richard Biener <rguent...@suse.de> writes:
>> >> >> > On Fri, 17 Dec 2021, Richard Sandiford wrote:
>> >> >> >
>> >> >> >> Prathamesh Kulkarni <prathamesh.kulka...@linaro.org> writes:
>> >> >> >> > Hi,
>> >> >> >> > The attached patch rearranges order of type-check for
>> >> >> >> > vec_perm_expr
>> >> >> >> > and relaxes type checking for
>> >> >> >> > lhs = vec_perm_expr<rhs1, rhs2, mask>
>> >> >> >> >
>> >> >> >> > when:
>> >> >> >> > rhs1 == rhs2,
>> >> >> >> > lhs is variable length vector,
>> >> >> >> > rhs1 is fixed length vector,
>> >> >> >> > TREE_TYPE (lhs) == TREE_TYPE (rhs1)
>> >> >> >> >
>> >> >> >> > I am not sure tho if this check is correct ? My intent was to
>> >> >> >> > capture
>> >> >> >> > case when vec_perm_expr is used to "extend" fixed length vector to
>> >> >> >> > it's VLA equivalent.
>> >> >> >>
>> >> >> >> VLAness isn't really the issue. We want the same thing to work for
>> >> >> >> -msve-vector-bits=256, -msve-vector-bits=512, etc., even though the
>> >> >> >> vectors are fixed-length in that case.
>> >> >> >>
>> >> >> >> The principle is that for:
>> >> >> >>
>> >> >> >> A = VEC_PERM_EXPR <B, C, D>;
>> >> >> >>
>> >> >> >> the requirements are:
>> >> >> >>
>> >> >> >> - A, B, C and D must be vectors
>> >> >> >> - A, B and C must have the same element type
>> >> >> >> - D must have an integer element type
>> >> >> >> - A and D must have the same number of elements (NA)
>> >> >> >> - B and C must have the same number of elements (NB)
>> >> >> >>
>> >> >> >> The semantics are that we create a joined vector BC (all elements
>> >> >> >> of B
>> >> >> >> followed by all element of C) and that:
>> >> >> >>
>> >> >> >> A[i] = BC[D[i] % (NB+NB)]
>> >> >> >>
>> >> >> >> for 0 ≤ i < NA.
>> >> >> >>
>> >> >> >> This operation makes sense even if NA != NB.
>> >> >> >
>> >> >> > But note that we don't currently expect NA != NB and the optab just
>> >> >> > has a single mode.
>> >> >>
>> >> >> True, but we only need this for constant permutes. They are already
>> >> >> special in that they allow the index elements to be wider than the data
>> >> >> elements.
>> >> >
>> >> > OK, then we should reflect this in the stmt verification and only relax
>> >> > the constant permute vector case and also amend the
>> >> > TARGET_VECTORIZE_VEC_PERM_CONST accordingly.
>> >>
>> >> Sounds good.
>> >>
>> >> > For non-constant permutes the docs say the mode of vec_perm is
>> >> > the common mode of operands 1 and 2 whilst the mode of operand 0
>> >> > is unspecified - even unconstrained by the docs. I'm not sure
>> >> > if vec_perm expansion is expected to eventually FAIL. Updating the
>> >> > docs of vec_perm would be appreciated as well.
>> >>
>> >> Yeah, I guess de facto operand 0 has to be the same mode as operands
>> >> 1 and 2. Maybe that was just an oversight, or maybe it seemed obvious
>> >> or self-explanatory at the time. :-)
>> >>
>> >> > As said I prefer to not mangle the existing stmt checking too much
>> >> > at this stage so minimal adjustment is prefered there.
>> >>
>> >> The PR is only an enhancement request rather than a bug, so I think the
>> >> patch would need to wait for GCC 13 whatever happens.
>> > Hi,
>> > In attached patch, the type checking is relaxed only if mask is constant.
>> > Does this look OK ?
>> >
>> > Thanks,
>> > Prathamesh
>> >>
>> >> Thanks,
>> >> Richard
>> >
>> > diff --git a/gcc/tree-cfg.cc b/gcc/tree-cfg.cc
>> > index e321d929fd0..02b88f67855 100644
>> > --- a/gcc/tree-cfg.cc
>> > +++ b/gcc/tree-cfg.cc
>> > @@ -4307,6 +4307,24 @@ verify_gimple_assign_ternary (gassign *stmt)
>> > break;
>> >
>> > case VEC_PERM_EXPR:
>> > + /* If permute is constant, then we allow for lhs and rhs
>> > + to have different vector types, provided:
>> > + (1) lhs, rhs1, rhs2, and rhs3 have same element type.
>>
>> This isn't a requirement for rhs3.
>>
>> > + (2) rhs3 vector has integer element type.
>> > + (3) len(lhs) == len(rhs3) && len(rhs1) == len(rhs2). */
>> > +
>> > + if (TREE_CONSTANT (rhs3)
>> > + && VECTOR_TYPE_P (lhs_type)
>> > + && VECTOR_TYPE_P (rhs1_type)
>> > + && VECTOR_TYPE_P (rhs2_type)
>> > + && VECTOR_TYPE_P (rhs3_type)
>> > + && TREE_TYPE (lhs_type) == TREE_TYPE (rhs1_type)
>> > + && TREE_TYPE (lhs_type) == TREE_TYPE (rhs2_type)
>> > + && INTEGRAL_TYPE_P (TREE_TYPE (rhs3_type))
>> > + && known_eq (TYPE_VECTOR_SUBPARTS (lhs_type), TYPE_VECTOR_SUBPARTS
>> > (rhs3_type))
>> > + && known_eq (TYPE_VECTOR_SUBPARTS (rhs1_type),
>> > TYPE_VECTOR_SUBPARTS (rhs2_type)))
>> > + return false;
>> > +
>>
>> I think this should be integrated into the existing conditions
>> rather than done as an initial special case.
>>
>> It might make sense to start with:
>>
>> if (TREE_CODE (rhs1_type) != VECTOR_TYPE
>> || TREE_CODE (rhs2_type) != VECTOR_TYPE
>> || TREE_CODE (rhs3_type) != VECTOR_TYPE)
>> {
>>
>> but expanded to test lhs_type too. Then the other parts of the new test
>> should be distributed across the existing conditions.
>>
>> The type tests should use useless_type_conversion_p rather than ==.
> Hi Richard,
> Thanks for the suggestions. In the attached patch, I tried to
> distribute the checks
> across existing conditions, does it look OK ?
> I am not sure how to write tests for the type checks tho, does
> gimple-fe support vec_perm_expr ?
> I did a quick testsuite run for vect.exp and the patch doesn't seem to
> cause any unexpected failures.
>
> Thanks,
> Prathamesh
>>
>> Thanks,
>> Richard
>>
>>
>>
>> > if (!useless_type_conversion_p (lhs_type, rhs1_type)
>> > || !useless_type_conversion_p (lhs_type, rhs2_type))
>> > {
>
> diff --git a/gcc/tree-cfg.cc b/gcc/tree-cfg.cc
> index e321d929fd0..a845c7fff93 100644
> --- a/gcc/tree-cfg.cc
> +++ b/gcc/tree-cfg.cc
> @@ -4307,18 +4307,14 @@ verify_gimple_assign_ternary (gassign *stmt)
> break;
>
> case VEC_PERM_EXPR:
> - if (!useless_type_conversion_p (lhs_type, rhs1_type)
> - || !useless_type_conversion_p (lhs_type, rhs2_type))
> - {
> - error ("type mismatch in %qs", code_name);
> - debug_generic_expr (lhs_type);
> - debug_generic_expr (rhs1_type);
> - debug_generic_expr (rhs2_type);
> - debug_generic_expr (rhs3_type);
> - return true;
> - }
> + /* If permute is constant, then we allow for lhs and rhs
> + to have different vector types, provided:
> + (1) lhs, rhs1, rhs2 have same element type.
> + (2) rhs3 vector has integer element type.
> + (3) len(lhs) == len(rhs3) && len(rhs1) == len(rhs2). */
>
> - if (TREE_CODE (rhs1_type) != VECTOR_TYPE
> + if (TREE_CODE (lhs_type) != VECTOR_TYPE
> + || TREE_CODE (rhs1_type) != VECTOR_TYPE
> || TREE_CODE (rhs2_type) != VECTOR_TYPE
> || TREE_CODE (rhs3_type) != VECTOR_TYPE)
> {
> @@ -4330,10 +4326,29 @@ verify_gimple_assign_ternary (gassign *stmt)
> return true;
> }
>
> + /* If lhs, rhs1, and rhs2 are different vector types,
> + then relax the check if rhs3 is constant and lhs, rhs1, and rhs2
> + have same element types. */
> + if ((!useless_type_conversion_p (lhs_type, rhs1_type)
> + || !useless_type_conversion_p (lhs_type, rhs2_type))
> + && (!TREE_CONSTANT (rhs3)
> + || TREE_TYPE (lhs_type) != TREE_TYPE (rhs1_type)
> + || TREE_TYPE (lhs_type) != TREE_TYPE (rhs2_type)))
These TREE_TYPE tests should use !useless_type_conversion_p too,
instead of !=. Maybe it would be easier to follow as:
if (TREE_CONSTANT (rhs3)
? ...
: ...)
so that we don't have doubled useless_type_conversion_p checks
for the TREE_CONSTANT case.
> + {
> + error ("type mismatch in %qs", code_name);
> + debug_generic_expr (lhs_type);
> + debug_generic_expr (rhs1_type);
> + debug_generic_expr (rhs2_type);
> + debug_generic_expr (rhs3_type);
> + return true;
> + }
> +
> + /* If rhs3 is constant, relax the check len(rhs2) == len(rhs3). */
> if (maybe_ne (TYPE_VECTOR_SUBPARTS (rhs1_type),
> TYPE_VECTOR_SUBPARTS (rhs2_type))
> - || maybe_ne (TYPE_VECTOR_SUBPARTS (rhs2_type),
> + || (maybe_ne (TYPE_VECTOR_SUBPARTS (rhs2_type),
> TYPE_VECTOR_SUBPARTS (rhs3_type))
> + && !TREE_CONSTANT (rhs3))
Very minor, but I think this reads better with the !TREE_CONSTANT first
in the && rather than second. There's no reason to compare the lengths
for TREE_CONSTANT.
Otherwise it looks good to me, but Richard should have the final say.
Thanks,
Richard
> || maybe_ne (TYPE_VECTOR_SUBPARTS (rhs3_type),
> TYPE_VECTOR_SUBPARTS (lhs_type)))
> {
