On Thu, May 16, 2024 at 10:40 PM Victor Do Nascimento
<victor.donascime...@arm.com> wrote:
>
> From: Victor Do Nascimento <vicdo...@e133397.arm.com>
>
> At present, the compiler offers the `{u|s|us}dot_prod_optab' direct
> optabs for dealing with vectorizable dot product code sequences. The
> consequence of using a direct optab for this is that backend-pattern
> selection is only ever able to match against one datatype - Either
> that of the operands or of the accumulated value, never both.
>
> With the introduction of the 2-way (un)signed dot-product insn [1][2]
> in AArch64 SVE2, the existing direct opcode approach is no longer
> sufficient for full specification of all the possible dot product
> machine instructions to be matched to the code sequence; a dot product
> resulting in VNx4SI may result from either dot products on VNx16QI or
> VNx8HI values for the 4- and 2-way dot product operations, respectively.
>
> This means that the following example fails autovectorization:
>
> uint32_t foo(int n, uint16_t* data) {
> uint32_t sum = 0;
> for (int i=0; i<n; i+=1) {
> sum += data[i] * data[i];
> }
> return sum;
> }
>
Sorry to chime in, for x86 backend, we defined usdot_prodv16hi, and
2-way dot_prod operations can be generated
> To remedy the issue a new optab is added, tentatively named
> `udot_prod_twoway_optab', whose selection is dependent upon checking
> of both input and output types involved in the operation.
>
> In order to minimize changes to the existing codebase,
> `optab_for_tree_code' is renamed `optab_for_tree_code_1' and a new
> argument is added to its signature - `const_tree otype', allowing type
> information to be specified for both input and output types. The
> existing nterface is retained by defining a new `optab_for_tree_code',
> which serves as a shim to `optab_for_tree_code_1', passing old
> parameters as-is and setting the new `optype' argument to `NULL_TREE'.
>
> For DOT_PROD_EXPR tree codes, we can call `optab_for_tree_code_1'
> directly, passing it both types, adding the internal logic to the
> function to distinguish between competing optabs.
>
> Finally, necessary changes are made to `expand_widen_pattern_expr' to
> ensure the new icode can be correctly selected, given the new optab.
>
> [1]
> https://developer.arm.com/documentation/ddi0602/2024-03/SVE-Instructions/UDOT--2-way--vectors---Unsigned-integer-dot-product-
> [2]
> https://developer.arm.com/documentation/ddi0602/2024-03/SVE-Instructions/SDOT--2-way--vectors---Signed-integer-dot-product-
>
> gcc/ChangeLog:
>
> * config/aarch64/aarch64-sve2.md (@aarch64_sve_<sur>dotvnx4sivnx8hi):
> renamed to `<sur>dot_prod_twoway_vnx8hi'.
> * config/aarch64/aarch64-sve-builtins-base.cc (svdot_impl.expand):
> update icodes used in line with above rename.
> * optabs-tree.cc (optab_for_tree_code_1): Renamed
> `optab_for_tree_code' and added new argument.
> (optab_for_tree_code): Now a call to `optab_for_tree_code_1'.
> * optabs-tree.h (optab_for_tree_code_1): New.
> * optabs.cc (expand_widen_pattern_expr): Expand support for
> DOT_PROD_EXPR patterns.
> * optabs.def (udot_prod_twoway_optab): New.
> (sdot_prod_twoway_optab): Likewise.
> * tree-vect-patterns.cc (vect_supportable_direct_optab_p): Add
> support for misc optabs that use two modes.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/vect/vect-dotprod-twoway.c: New.
> ---
> .../aarch64/aarch64-sve-builtins-base.cc | 4 ++--
> gcc/config/aarch64/aarch64-sve2.md | 2 +-
> gcc/optabs-tree.cc | 23 ++++++++++++++++--
> gcc/optabs-tree.h | 2 ++
> gcc/optabs.cc | 2 +-
> gcc/optabs.def | 2 ++
> .../gcc.dg/vect/vect-dotprod-twoway.c | 24 +++++++++++++++++++
> gcc/tree-vect-patterns.cc | 2 +-
> 8 files changed, 54 insertions(+), 7 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/vect/vect-dotprod-twoway.c
>
> diff --git a/gcc/config/aarch64/aarch64-sve-builtins-base.cc
> b/gcc/config/aarch64/aarch64-sve-builtins-base.cc
> index 0d2edf3f19e..e457db09f66 100644
> --- a/gcc/config/aarch64/aarch64-sve-builtins-base.cc
> +++ b/gcc/config/aarch64/aarch64-sve-builtins-base.cc
> @@ -764,8 +764,8 @@ public:
> icode = (e.type_suffix (0).float_p
> ? CODE_FOR_aarch64_sve_fdotvnx4sfvnx8hf
> : e.type_suffix (0).unsigned_p
> - ? CODE_FOR_aarch64_sve_udotvnx4sivnx8hi
> - : CODE_FOR_aarch64_sve_sdotvnx4sivnx8hi);
> + ? CODE_FOR_udot_prod_twoway_vnx8hi
> + : CODE_FOR_sdot_prod_twoway_vnx8hi);
> return e.use_unpred_insn (icode);
> }
> };
> diff --git a/gcc/config/aarch64/aarch64-sve2.md
> b/gcc/config/aarch64/aarch64-sve2.md
> index 934e57055d3..5677de7108d 100644
> --- a/gcc/config/aarch64/aarch64-sve2.md
> +++ b/gcc/config/aarch64/aarch64-sve2.md
> @@ -2021,7 +2021,7 @@ (define_insn
> "@aarch64_sve_qsub_<sve_int_op>_lane_<mode>"
> )
>
> ;; Two-way dot-product.
> -(define_insn "@aarch64_sve_<sur>dotvnx4sivnx8hi"
> +(define_insn "<sur>dot_prod_twoway_vnx8hi"
> [(set (match_operand:VNx4SI 0 "register_operand")
> (plus:VNx4SI
> (unspec:VNx4SI
> diff --git a/gcc/optabs-tree.cc b/gcc/optabs-tree.cc
> index b69a5bc3676..e3c5a618ea2 100644
> --- a/gcc/optabs-tree.cc
> +++ b/gcc/optabs-tree.cc
> @@ -35,8 +35,8 @@ along with GCC; see the file COPYING3. If not see
> cannot give complete results for multiplication or division) but probably
> ought to be relied on more widely throughout the expander. */
> optab
> -optab_for_tree_code (enum tree_code code, const_tree type,
> - enum optab_subtype subtype)
> +optab_for_tree_code_1 (enum tree_code code, const_tree type,
> + const_tree otype, enum optab_subtype subtype)
> {
> bool trapv;
> switch (code)
> @@ -149,6 +149,14 @@ optab_for_tree_code (enum tree_code code, const_tree
> type,
>
> case DOT_PROD_EXPR:
> {
> + if (otype && (TYPE_PRECISION (TREE_TYPE (type)) * 2
> + == TYPE_PRECISION (TREE_TYPE (otype))))
> + {
> + if (TYPE_UNSIGNED (type) && TYPE_UNSIGNED (otype))
> + return udot_prod_twoway_optab;
> + if (!TYPE_UNSIGNED (type) && !TYPE_UNSIGNED (otype))
> + return sdot_prod_twoway_optab;
> + }
> if (subtype == optab_vector_mixed_sign)
> return usdot_prod_optab;
>
> @@ -285,6 +293,17 @@ optab_for_tree_code (enum tree_code code, const_tree
> type,
> }
> }
>
> +/* Return the optab used for computing the operation given by the tree code,
> + CODE and the tree EXP. This function is not always usable (for example,
> it
> + cannot give complete results for multiplication or division) but probably
> + ought to be relied on more widely throughout the expander. */
> +optab
> +optab_for_tree_code (enum tree_code code, const_tree type,
> + enum optab_subtype subtype)
> +{
> + return optab_for_tree_code_1 (code, type, NULL_TREE, subtype);
> +}
> +
> /* Check whether an operation represented by CODE is a 'half' widening
> operation
> in which the input vector type has half the number of bits of the output
> vector type e.g. V8QI->V8HI.
> diff --git a/gcc/optabs-tree.h b/gcc/optabs-tree.h
> index f2b49991462..13ff7ca2e4b 100644
> --- a/gcc/optabs-tree.h
> +++ b/gcc/optabs-tree.h
> @@ -36,6 +36,8 @@ enum optab_subtype
> /* Return the optab used for computing the given operation on the type given
> by
> the second argument. The third argument distinguishes between the types
> of
> vector shifts and rotates. */
> +optab optab_for_tree_code_1 (enum tree_code, const_tree, const_tree
> __attribute__((unused)),
> + enum optab_subtype );
> optab optab_for_tree_code (enum tree_code, const_tree, enum optab_subtype);
> bool
> supportable_half_widening_operation (enum tree_code, tree, tree,
> diff --git a/gcc/optabs.cc b/gcc/optabs.cc
> index ce91f94ed43..3a1c6c7b90e 100644
> --- a/gcc/optabs.cc
> +++ b/gcc/optabs.cc
> @@ -311,7 +311,7 @@ expand_widen_pattern_expr (sepops ops, rtx op0, rtx op1,
> rtx wide_op,
> gcc_unreachable ();
>
> widen_pattern_optab
> - = optab_for_tree_code (ops->code, TREE_TYPE (oprnd0), subtype);
> + = optab_for_tree_code_1 (ops->code, TREE_TYPE (oprnd0), TREE_TYPE
> (oprnd2), subtype);
> }
> else
> widen_pattern_optab
> diff --git a/gcc/optabs.def b/gcc/optabs.def
> index ad14f9328b9..cf1a6e7a7dc 100644
> --- a/gcc/optabs.def
> +++ b/gcc/optabs.def
> @@ -408,6 +408,8 @@ OPTAB_D (sdot_prod_optab, "sdot_prod$I$a")
> OPTAB_D (ssum_widen_optab, "widen_ssum$I$a3")
> OPTAB_D (udot_prod_optab, "udot_prod$I$a")
> OPTAB_D (usdot_prod_optab, "usdot_prod$I$a")
> +OPTAB_D (sdot_prod_twoway_optab, "sdot_prod_twoway_$I$a")
> +OPTAB_D (udot_prod_twoway_optab, "udot_prod_twoway_$I$a")
> OPTAB_D (usum_widen_optab, "widen_usum$I$a3")
> OPTAB_D (usad_optab, "usad$I$a")
> OPTAB_D (ssad_optab, "ssad$I$a")
> diff --git a/gcc/testsuite/gcc.dg/vect/vect-dotprod-twoway.c
> b/gcc/testsuite/gcc.dg/vect/vect-dotprod-twoway.c
> new file mode 100644
> index 00000000000..cba2aadbec8
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/vect-dotprod-twoway.c
> @@ -0,0 +1,24 @@
> +/* { dg-do compile { target { aarch64*-*-* } } } */
> +/* { dg-additional-options "-march=-O3 -march=armv9.2-a+sme2
> -fdump-tree-vect-details" { target { aarch64*-*-* } } } */
> +
> +#include <stdint.h>
> +
> +uint32_t udot2(int n, uint16_t* data) {
> + uint32_t sum = 0;
> + for (int i=0; i<n; i+=1) {
> + sum += data[i] * data[i];
> + }
> + return sum;
> +}
> +
> +int32_t sdot2(int n, int16_t* data) {
> + int32_t sum = 0;
> + for (int i=0; i<n; i+=1) {
> + sum += data[i] * data[i];
> + }
> + return sum;
> +}
> +
> +/* { dg-final { scan-tree-dump-times "vect_recog_dot_prod_pattern:
> detected:" 2 "vect" } } */
> +/* { dg-final { scan-tree-dump-times "vect_recog_widen_mult_pattern:
> detected" 4 "vect" } } */
> +/* { dg-final { scan-tree-dump-times "vectorized 1 loops" 2 "vect" } } */
> diff --git a/gcc/tree-vect-patterns.cc b/gcc/tree-vect-patterns.cc
> index dfb7d800526..0760f25d94d 100644
> --- a/gcc/tree-vect-patterns.cc
> +++ b/gcc/tree-vect-patterns.cc
> @@ -233,7 +233,7 @@ vect_supportable_direct_optab_p (vec_info *vinfo, tree
> otype, tree_code code,
> if (!vecotype)
> return false;
>
> - optab optab = optab_for_tree_code (code, vecitype, subtype);
> + optab optab = optab_for_tree_code_1 (code, vecitype, vecotype, subtype);
> if (!optab)
> return false;
>
> --
> 2.34.1
>
--
BR,
Hongtao
