Richard Biener <rguent...@suse.de> writes:
> This adds a gather vectorization capability to the vectorizer
> without target support by decomposing the offset vector, doing
> sclar loads and then building a vector from the result. This
> is aimed mainly at cases where vectorizing the rest of the loop
> offsets the cost of vectorizing the gather.
>
> Note it's difficult to avoid vectorizing the offset load, but in
> some cases later passes can turn the vector load + extract into
> scalar loads, see the followup patch.
>
> On SPEC CPU 2017 510.parest_r this improves runtime from 250s
> to 219s on a Zen2 CPU which has its native gather instructions
> disabled (using those the runtime instead increases to 254s)
> using -Ofast -march=znver2 [-flto]. It turns out the critical
> loops in this benchmark all perform gather operations.
Nice!
> Bootstrapped and tested on x86_64-unknown-linux-gnu.
>
> Any comments? I still plan to run this over full SPEC and
> I have to apply TLC to the followup patch before I can post it.
>
> I think neither power nor z has gather so I'm curious if the
> patch helps 510.parest_r there, I'm unsure about neon/advsimd.
> Both might need the followup patch - I was surprised about
> the speedup without it on Zen (the followup improves runtime
> to 198s there).
>
> Thanks,
> Richard.
>
> 2021-07-30 Richard Biener <rguent...@suse.de>
>
> * tree-vect-data-refs.c (vect_check_gather_scatter):
> Include widening conversions only when the result is
> still handed by native gather or the current offset
> size not already matches the data size.
> Also succeed analysis in case there's no native support,
> noted by a IFN_LAST ifn and a NULL decl.
> * tree-vect-patterns.c (vect_recog_gather_scatter_pattern):
> Test for no IFN gather rather than decl gather.
> * tree-vect-stmts.c (vect_model_load_cost): Pass in the
> gather-scatter info and cost emulated gathers accordingly.
> (vect_truncate_gather_scatter_offset): Properly test for
> no IFN gather.
> (vect_use_strided_gather_scatters_p): Likewise.
> (get_load_store_type): Handle emulated gathers and its
> restrictions.
> (vectorizable_load): Likewise. Emulate them by extracting
> scalar offsets, doing scalar loads and a vector construct.
>
> * gcc.target/i386/vect-gather-1.c: New testcase.
> * gfortran.dg/vect/vect-8.f90: Adjust.
> ---
> gcc/testsuite/gcc.target/i386/vect-gather-1.c | 18 ++++
> gcc/testsuite/gfortran.dg/vect/vect-8.f90 | 2 +-
> gcc/tree-vect-data-refs.c | 29 +++--
> gcc/tree-vect-patterns.c | 2 +-
> gcc/tree-vect-stmts.c | 100 ++++++++++++++++--
> 5 files changed, 136 insertions(+), 15 deletions(-)
> create mode 100644 gcc/testsuite/gcc.target/i386/vect-gather-1.c
>
> diff --git a/gcc/testsuite/gcc.target/i386/vect-gather-1.c
> b/gcc/testsuite/gcc.target/i386/vect-gather-1.c
> new file mode 100644
> index 00000000000..134aef39666
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/vect-gather-1.c
> @@ -0,0 +1,18 @@
> +/* { dg-do compile } */
> +/* { dg-options "-Ofast -msse2 -fdump-tree-vect-details" } */
> +
> +#ifndef INDEXTYPE
> +#define INDEXTYPE int
> +#endif
> +double vmul(INDEXTYPE *rowstart, INDEXTYPE *rowend,
> + double *luval, double *dst)
> +{
> + double res = 0;
> + for (const INDEXTYPE * col = rowstart; col != rowend; ++col, ++luval)
> + res += *luval * dst[*col];
> + return res;
> +}
> +
> +/* With gather emulation this should be profitable to vectorize
> + even with plain SSE2. */
> +/* { dg-final { scan-tree-dump "loop vectorized" "vect" } } */
> diff --git a/gcc/testsuite/gfortran.dg/vect/vect-8.f90
> b/gcc/testsuite/gfortran.dg/vect/vect-8.f90
> index 9994805d77f..cc1aebfbd84 100644
> --- a/gcc/testsuite/gfortran.dg/vect/vect-8.f90
> +++ b/gcc/testsuite/gfortran.dg/vect/vect-8.f90
> @@ -706,5 +706,5 @@ END SUBROUTINE kernel
>
> ! { dg-final { scan-tree-dump-times "vectorized 24 loops" 1 "vect" { target
> aarch64_sve } } }
> ! { dg-final { scan-tree-dump-times "vectorized 23 loops" 1 "vect" { target
> { aarch64*-*-* && { ! aarch64_sve } } } } }
> -! { dg-final { scan-tree-dump-times "vectorized 2\[23\] loops" 1 "vect" {
> target { vect_intdouble_cvt && { ! aarch64*-*-* } } } } }
> +! { dg-final { scan-tree-dump-times "vectorized 2\[234\] loops" 1 "vect" {
> target { vect_intdouble_cvt && { ! aarch64*-*-* } } } } }
> ! { dg-final { scan-tree-dump-times "vectorized 17 loops" 1 "vect" { target
> { { ! vect_intdouble_cvt } && { ! aarch64*-*-* } } } } }
> diff --git a/gcc/tree-vect-data-refs.c b/gcc/tree-vect-data-refs.c
> index 6995efba899..0279e75fa8e 100644
> --- a/gcc/tree-vect-data-refs.c
> +++ b/gcc/tree-vect-data-refs.c
> @@ -4007,8 +4007,26 @@ vect_check_gather_scatter (stmt_vec_info stmt_info,
> loop_vec_info loop_vinfo,
> continue;
> }
>
> - if (TYPE_PRECISION (TREE_TYPE (op0))
> - < TYPE_PRECISION (TREE_TYPE (off)))
> + /* Include the conversion if it is widening and we're using
> + the IFN path or the target can handle the converted from
> + offset or the current size is not already the same as the
> + data vector element size. */
> + if ((TYPE_PRECISION (TREE_TYPE (op0))
> + < TYPE_PRECISION (TREE_TYPE (off)))
> + && ((!use_ifn_p
> + && (DR_IS_READ (dr)
> + ? (targetm.vectorize.builtin_gather
> + && targetm.vectorize.builtin_gather (vectype,
> + TREE_TYPE (op0),
> + scale))
> + : (targetm.vectorize.builtin_scatter
> + && targetm.vectorize.builtin_scatter (vectype,
> + TREE_TYPE (op0),
> + scale))))
> + || (!use_ifn_p
> + && !operand_equal_p (TYPE_SIZE (TREE_TYPE (off)),
> + TYPE_SIZE (TREE_TYPE (vectype)),
> + 0))))
I don't understand this bit: it seems to disable the path for
use_ifn_p altogether.
> {
> off = op0;
> offtype = TREE_TYPE (off);
> @@ -4036,7 +4054,8 @@ vect_check_gather_scatter (stmt_vec_info stmt_info,
> loop_vec_info loop_vinfo,
> if (!vect_gather_scatter_fn_p (loop_vinfo, DR_IS_READ (dr), masked_p,
> vectype, memory_type, offtype, scale,
> &ifn, &offset_vectype))
> - return false;
> + ifn = IFN_LAST;
> + decl = NULL_TREE;
> }
> else
> {
> @@ -4050,10 +4069,6 @@ vect_check_gather_scatter (stmt_vec_info stmt_info,
> loop_vec_info loop_vinfo,
> if (targetm.vectorize.builtin_scatter)
> decl = targetm.vectorize.builtin_scatter (vectype, offtype, scale);
> }
> -
> - if (!decl)
> - return false;
> -
> ifn = IFN_LAST;
> /* The offset vector type will be read from DECL when needed. */
> offset_vectype = NULL_TREE;
> diff --git a/gcc/tree-vect-patterns.c b/gcc/tree-vect-patterns.c
> index 743fd3f5414..25de97bd9b0 100644
> --- a/gcc/tree-vect-patterns.c
> +++ b/gcc/tree-vect-patterns.c
> @@ -4811,7 +4811,7 @@ vect_recog_gather_scatter_pattern (vec_info *vinfo,
> function for the gather/scatter operation. */
> gather_scatter_info gs_info;
> if (!vect_check_gather_scatter (stmt_info, loop_vinfo, &gs_info)
> - || gs_info.decl)
> + || gs_info.ifn == IFN_LAST)
> return NULL;
>
> /* Convert the mask to the right form. */
> diff --git a/gcc/tree-vect-stmts.c b/gcc/tree-vect-stmts.c
> index 05085e1b110..9d51b476db6 100644
> --- a/gcc/tree-vect-stmts.c
> +++ b/gcc/tree-vect-stmts.c
> @@ -1084,6 +1084,7 @@ static void
> vect_model_load_cost (vec_info *vinfo,
> stmt_vec_info stmt_info, unsigned ncopies, poly_uint64 vf,
> vect_memory_access_type memory_access_type,
> + gather_scatter_info *gs_info,
> slp_tree slp_node,
> stmt_vector_for_cost *cost_vec)
> {
> @@ -1172,9 +1173,17 @@ vect_model_load_cost (vec_info *vinfo,
> if (memory_access_type == VMAT_ELEMENTWISE
> || memory_access_type == VMAT_GATHER_SCATTER)
> {
> - /* N scalar loads plus gathering them into a vector. */
> tree vectype = STMT_VINFO_VECTYPE (stmt_info);
> unsigned int assumed_nunits = vect_nunits_for_cost (vectype);
> + if (memory_access_type == VMAT_GATHER_SCATTER
> + && gs_info->ifn == IFN_LAST && !gs_info->decl)
> + /* For emulated gathers N offset vector element extracts
> + (we assume the scalar scaling and ptr + offset add is consumed by
> + the load). */
> + inside_cost += record_stmt_cost (cost_vec, ncopies * assumed_nunits,
> + vec_to_scalar, stmt_info, 0,
> + vect_body);
> + /* N scalar loads plus gathering them into a vector. */
> inside_cost += record_stmt_cost (cost_vec,
> ncopies * assumed_nunits,
> scalar_load, stmt_info, 0, vect_body);
> @@ -1184,7 +1193,9 @@ vect_model_load_cost (vec_info *vinfo,
> &inside_cost, &prologue_cost,
> cost_vec, cost_vec, true);
> if (memory_access_type == VMAT_ELEMENTWISE
> - || memory_access_type == VMAT_STRIDED_SLP)
> + || memory_access_type == VMAT_STRIDED_SLP
> + || (memory_access_type == VMAT_GATHER_SCATTER
> + && gs_info->ifn == IFN_LAST && !gs_info->decl))
> inside_cost += record_stmt_cost (cost_vec, ncopies, vec_construct,
> stmt_info, 0, vect_body);
>
> @@ -1866,7 +1877,8 @@ vect_truncate_gather_scatter_offset (stmt_vec_info
> stmt_info,
> tree memory_type = TREE_TYPE (DR_REF (dr));
> if (!vect_gather_scatter_fn_p (loop_vinfo, DR_IS_READ (dr), masked_p,
> vectype, memory_type, offset_type, scale,
> - &gs_info->ifn, &gs_info->offset_vectype))
> + &gs_info->ifn, &gs_info->offset_vectype)
> + || gs_info->ifn == IFN_LAST)
> continue;
>
> gs_info->decl = NULL_TREE;
> @@ -1901,7 +1913,7 @@ vect_use_strided_gather_scatters_p (stmt_vec_info
> stmt_info,
> gather_scatter_info *gs_info)
> {
> if (!vect_check_gather_scatter (stmt_info, loop_vinfo, gs_info)
> - || gs_info->decl)
> + || gs_info->ifn == IFN_LAST)
> return vect_truncate_gather_scatter_offset (stmt_info, loop_vinfo,
> masked_p, gs_info);
>
> @@ -2355,6 +2367,27 @@ get_load_store_type (vec_info *vinfo, stmt_vec_info
> stmt_info,
> vls_type == VLS_LOAD ? "gather" : "scatter");
> return false;
> }
> + else if (gs_info->ifn == IFN_LAST && !gs_info->decl)
> + {
> + if (vls_type != VLS_LOAD)
> + {
> + if (dump_enabled_p ())
> + dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
> + "unsupported emulated scatter.\n");
> + return false;
> + }
> + else if (!TYPE_VECTOR_SUBPARTS (vectype).is_constant ()
> + || !known_eq (TYPE_VECTOR_SUBPARTS (vectype),
> + TYPE_VECTOR_SUBPARTS
> + (gs_info->offset_vectype)))
> + {
> + if (dump_enabled_p ())
> + dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
> + "unsupported vector types for emulated "
> + "gather.\n");
> + return false;
> + }
> + }
> /* Gather-scatter accesses perform only component accesses, alignment
> is irrelevant for them. */
> *alignment_support_scheme = dr_unaligned_supported;
> @@ -8692,6 +8725,15 @@ vectorizable_load (vec_info *vinfo,
> "unsupported access type for masked load.\n");
> return false;
> }
> + else if (memory_access_type == VMAT_GATHER_SCATTER
> + && gs_info.ifn == IFN_LAST
> + && !gs_info.decl)
> + {
> + if (dump_enabled_p ())
> + dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
> + "unsupported masked emulated gather.\n");
> + return false;
> + }
> }
>
> if (!vec_stmt) /* transformation not required. */
> @@ -8725,7 +8767,7 @@ vectorizable_load (vec_info *vinfo,
>
> STMT_VINFO_TYPE (orig_stmt_info) = load_vec_info_type;
> vect_model_load_cost (vinfo, stmt_info, ncopies, vf,
> memory_access_type,
> - slp_node, cost_vec);
> + &gs_info, slp_node, cost_vec);
> return true;
> }
>
> @@ -9438,7 +9480,8 @@ vectorizable_load (vec_info *vinfo,
> unsigned int misalign;
> unsigned HOST_WIDE_INT align;
>
> - if (memory_access_type == VMAT_GATHER_SCATTER)
> + if (memory_access_type == VMAT_GATHER_SCATTER
> + && gs_info.ifn != IFN_LAST)
> {
> tree zero = build_zero_cst (vectype);
> tree scale = size_int (gs_info.scale);
> @@ -9456,6 +9499,51 @@ vectorizable_load (vec_info *vinfo,
> data_ref = NULL_TREE;
> break;
> }
> + else if (memory_access_type == VMAT_GATHER_SCATTER)
> + {
> + /* Emulated gather-scatter. */
> + gcc_assert (!final_mask);
For this to be safe, we need to make sure that
check_load_store_for_partial_vectors clears
LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P. Is that already guaranteed?
(Maybe yes, I didn't look closely. :-))
LGTM otherwise FWIW.
Thanks,
Richard
> + unsigned HOST_WIDE_INT const_nunits
> + = nunits.to_constant ();
> + vec<constructor_elt, va_gc> *ctor_elts;
> + vec_alloc (ctor_elts, const_nunits);
> + gimple_seq stmts = NULL;
> + tree idx_type = TREE_TYPE (TREE_TYPE (vec_offset));
> + tree scale = size_int (gs_info.scale);
> + align
> + = get_object_alignment (DR_REF (first_dr_info->dr));
> + tree ltype = build_aligned_type (TREE_TYPE (vectype),
> + align);
> + for (unsigned k = 0; k < const_nunits; ++k)
> + {
> + tree boff = size_binop (MULT_EXPR,
> + TYPE_SIZE (idx_type),
> + bitsize_int (k));
> + tree idx = gimple_build (&stmts, BIT_FIELD_REF,
> + idx_type, vec_offset,
> + TYPE_SIZE (idx_type),
> + boff);
> + idx = gimple_convert (&stmts, sizetype, idx);
> + idx = gimple_build (&stmts, MULT_EXPR,
> + sizetype, idx, scale);
> + tree ptr = gimple_build (&stmts, PLUS_EXPR,
> + TREE_TYPE (dataref_ptr),
> + dataref_ptr, idx);
> + ptr = gimple_convert (&stmts, ptr_type_node, ptr);
> + tree elt = make_ssa_name (TREE_TYPE (vectype));
> + tree ref = build2 (MEM_REF, ltype, ptr,
> + build_int_cst (ref_type, 0));
> + new_stmt = gimple_build_assign (elt, ref);
> + gimple_seq_add_stmt (&stmts, new_stmt);
> + CONSTRUCTOR_APPEND_ELT (ctor_elts, NULL_TREE, elt);
> + }
> + gsi_insert_seq_before (gsi, stmts, GSI_SAME_STMT);
> + new_stmt = gimple_build_assign (NULL_TREE,
> + build_constructor
> + (vectype, ctor_elts));
> + data_ref = NULL_TREE;
> + break;
> + }
>
> align =
> known_alignment (DR_TARGET_ALIGNMENT (first_dr_info));
