[PATCH 1/2] Add emulated gather capability to the vectorizer

[PATCH 1/2] Add emulated gather capability to the vectorizer

[Richard Biener]

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.

Bootstrapped and tested on x86_64-unknown-linux-gnu.

2021-07-30  Richard Biener  <rguenther@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.
	(vect_analyze_data_refs): Always consider gathers.
	* 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                     |  34 ++++--
 gcc/tree-vect-patterns.c                      |   2 +-
 gcc/tree-vect-stmts.c                         | 100 ++++++++++++++++--
 5 files changed, 138 insertions(+), 18 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..3c29ff04fd8 100644
--- a/gcc/tree-vect-data-refs.c
+++ b/gcc/tree-vect-data-refs.c
@@ -4007,8 +4007,27 @@ 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))
+		  || use_ifn_p))
 	    {
 	      off = op0;
 	      offtype = TREE_TYPE (off);
@@ -4036,7 +4055,8 @@ 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 +4070,6 @@ 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;
@@ -4283,9 +4299,7 @@ vect_analyze_data_refs (vec_info *vinfo, poly_uint64 *min_vf, bool *fatal)
         {
 	  bool maybe_gather
 	    = DR_IS_READ (dr)
-	      && !TREE_THIS_VOLATILE (DR_REF (dr))
-	      && (targetm.vectorize.builtin_gather != NULL
-		  || supports_vec_gather_load_p ());
+	      && !TREE_THIS_VOLATILE (DR_REF (dr));
 	  bool maybe_scatter
 	    = DR_IS_WRITE (dr)
 	      && !TREE_THIS_VOLATILE (DR_REF (dr))
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);
+			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));
-- 
2.31.1

Re: [PATCH 1/2] Add emulated gather capability to the vectorizer

[Richard Sandiford]

Richard Biener <rguenther@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.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu.
>
> 2021-07-30  Richard Biener  <rguenther@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.
> 	(vect_analyze_data_refs): Always consider gathers.
> 	* 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                     |  34 ++++--
>  gcc/tree-vect-patterns.c                      |   2 +-
>  gcc/tree-vect-stmts.c                         | 100 ++++++++++++++++--
>  5 files changed, 138 insertions(+), 18 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..3c29ff04fd8 100644
> --- a/gcc/tree-vect-data-refs.c
> +++ b/gcc/tree-vect-data-refs.c
> @@ -4007,8 +4007,27 @@ 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))
> +		  || use_ifn_p))

Looks like this would be slightly simpler to read/understand as:

    && (use_ifn_p
        || (DR_IS_READ …)
        || !operand_equal_p …)

(Sorry for the unsubstantive comment.)

Richard

>  	    {
>  	      off = op0;
>  	      offtype = TREE_TYPE (off);
> @@ -4036,7 +4055,8 @@ 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 +4070,6 @@ 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;
> @@ -4283,9 +4299,7 @@ vect_analyze_data_refs (vec_info *vinfo, poly_uint64 *min_vf, bool *fatal)
>          {
>  	  bool maybe_gather
>  	    = DR_IS_READ (dr)
> -	      && !TREE_THIS_VOLATILE (DR_REF (dr))
> -	      && (targetm.vectorize.builtin_gather != NULL
> -		  || supports_vec_gather_load_p ());
> +	      && !TREE_THIS_VOLATILE (DR_REF (dr));
>  	  bool maybe_scatter
>  	    = DR_IS_WRITE (dr)
>  	      && !TREE_THIS_VOLATILE (DR_REF (dr))
> 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);
> +			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));

Re: [PATCH 1/2] Add emulated gather capability to the vectorizer

[Richard Biener]

On Wed, 4 Aug 2021, Richard Sandiford wrote:

> Richard Biener <rguenther@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.
> >
> > Bootstrapped and tested on x86_64-unknown-linux-gnu.
> >
> > 2021-07-30  Richard Biener  <rguenther@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.
> > 	(vect_analyze_data_refs): Always consider gathers.
> > 	* 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                     |  34 ++++--
> >  gcc/tree-vect-patterns.c                      |   2 +-
> >  gcc/tree-vect-stmts.c                         | 100 ++++++++++++++++--
> >  5 files changed, 138 insertions(+), 18 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..3c29ff04fd8 100644
> > --- a/gcc/tree-vect-data-refs.c
> > +++ b/gcc/tree-vect-data-refs.c
> > @@ -4007,8 +4007,27 @@ 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))
> > +		  || use_ifn_p))
> 
> Looks like this would be slightly simpler to read/understand as:
> 
>     && (use_ifn_p
>         || (DR_IS_READ …)
>         || !operand_equal_p …)
> 
> (Sorry for the unsubstantive comment.)

Ah, yes.  Will adjust before committing.

Thanks,
Richard.

> Richard
> 
> >  	    {
> >  	      off = op0;
> >  	      offtype = TREE_TYPE (off);
> > @@ -4036,7 +4055,8 @@ 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 +4070,6 @@ 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;
> > @@ -4283,9 +4299,7 @@ vect_analyze_data_refs (vec_info *vinfo, poly_uint64 *min_vf, bool *fatal)
> >          {
> >  	  bool maybe_gather
> >  	    = DR_IS_READ (dr)
> > -	      && !TREE_THIS_VOLATILE (DR_REF (dr))
> > -	      && (targetm.vectorize.builtin_gather != NULL
> > -		  || supports_vec_gather_load_p ());
> > +	      && !TREE_THIS_VOLATILE (DR_REF (dr));
> >  	  bool maybe_scatter
> >  	    = DR_IS_WRITE (dr)
> >  	      && !TREE_THIS_VOLATILE (DR_REF (dr))
> > 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);
> > +			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));
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)

Re: [PATCH 1/2] Add emulated gather capability to the vectorizer

[Christophe Lyon]

On Wed, Aug 4, 2021 at 2:08 PM Richard Biener <rguenther@suse.de> wrote:

> On Wed, 4 Aug 2021, Richard Sandiford wrote:
>
> > Richard Biener <rguenther@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.
> > >
> > > Bootstrapped and tested on x86_64-unknown-linux-gnu.
> > >
> > > 2021-07-30  Richard Biener  <rguenther@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.
> > >     (vect_analyze_data_refs): Always consider gathers.
> > >     * 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.
>

Hi,

The adjusted testcase now fails on aarch64:
FAIL:  gfortran.dg/vect/vect-8.f90   -O   scan-tree-dump-times vect
"vectorized 23 loops" 1


Christophe

> > ---
> > >  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                     |  34 ++++--
> > >  gcc/tree-vect-patterns.c                      |   2 +-
> > >  gcc/tree-vect-stmts.c                         | 100 ++++++++++++++++--
> > >  5 files changed, 138 insertions(+), 18 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..3c29ff04fd8 100644
> > > --- a/gcc/tree-vect-data-refs.c
> > > +++ b/gcc/tree-vect-data-refs.c
> > > @@ -4007,8 +4007,27 @@ 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))
> > > +             || use_ifn_p))
> >
> > Looks like this would be slightly simpler to read/understand as:
> >
> >     && (use_ifn_p
> >         || (DR_IS_READ …)
> >         || !operand_equal_p …)
> >
> > (Sorry for the unsubstantive comment.)
>
> Ah, yes.  Will adjust before committing.
>
> Thanks,
> Richard.
>
> > Richard
> >
> > >         {
> > >           off = op0;
> > >           offtype = TREE_TYPE (off);
> > > @@ -4036,7 +4055,8 @@ 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 +4070,6 @@ 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;
> > > @@ -4283,9 +4299,7 @@ vect_analyze_data_refs (vec_info *vinfo,
> poly_uint64 *min_vf, bool *fatal)
> > >          {
> > >       bool maybe_gather
> > >         = DR_IS_READ (dr)
> > > -         && !TREE_THIS_VOLATILE (DR_REF (dr))
> > > -         && (targetm.vectorize.builtin_gather != NULL
> > > -             || supports_vec_gather_load_p ());
> > > +         && !TREE_THIS_VOLATILE (DR_REF (dr));
> > >       bool maybe_scatter
> > >         = DR_IS_WRITE (dr)
> > >           && !TREE_THIS_VOLATILE (DR_REF (dr))
> > > 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);
> > > +                   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));
> >
>
> --
> Richard Biener <rguenther@suse.de>
> SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
> Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
>

Re: [PATCH 1/2] Add emulated gather capability to the vectorizer

[Richard Biener]

On Thu, 5 Aug 2021, Christophe Lyon wrote:

> On Wed, Aug 4, 2021 at 2:08 PM Richard Biener <rguenther@suse.de> wrote:
> 
> > On Wed, 4 Aug 2021, Richard Sandiford wrote:
> >
> > > Richard Biener <rguenther@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.
> > > >
> > > > Bootstrapped and tested on x86_64-unknown-linux-gnu.
> > > >
> > > > 2021-07-30  Richard Biener  <rguenther@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.
> > > >     (vect_analyze_data_refs): Always consider gathers.
> > > >     * 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.
> >
> 
> Hi,
> 
> The adjusted testcase now fails on aarch64:
> FAIL:  gfortran.dg/vect/vect-8.f90   -O   scan-tree-dump-times vect
> "vectorized 23 loops" 1

That likely means it needs adjustment for the aarch64 case as well
which I didn't touch.  I suppose it's now vectorizing 24 loops?
And 24 with SVE as well, so we might be able to merge the
aarch64_sve and aarch64 && ! aarch64_sve cases?

Like with

diff --git a/gcc/testsuite/gfortran.dg/vect/vect-8.f90 
b/gcc/testsuite/gfortran.dg/vect/vect-8.f90
index cc1aebfbd84..c8a7d896bac 100644
--- a/gcc/testsuite/gfortran.dg/vect/vect-8.f90
+++ b/gcc/testsuite/gfortran.dg/vect/vect-8.f90
@@ -704,7 +704,6 @@ CALL track('KERNEL  ')
 RETURN
 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 24 loops" 1 "vect" { 
target 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*-*-* } } } } }

f951 vect.exp testing with and without -march=armv8.3-a+sve shows
this might work, but if you can double-check that would be nice.

Richard.

Re: [PATCH 1/2] Add emulated gather capability to the vectorizer

[Christophe Lyon]

On Thu, Aug 5, 2021 at 11:53 AM Richard Biener <rguenther@suse.de> wrote:

> On Thu, 5 Aug 2021, Christophe Lyon wrote:
>
> > On Wed, Aug 4, 2021 at 2:08 PM Richard Biener <rguenther@suse.de> wrote:
> >
> > > On Wed, 4 Aug 2021, Richard Sandiford wrote:
> > >
> > > > Richard Biener <rguenther@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.
> > > > >
> > > > > Bootstrapped and tested on x86_64-unknown-linux-gnu.
> > > > >
> > > > > 2021-07-30  Richard Biener  <rguenther@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.
> > > > >     (vect_analyze_data_refs): Always consider gathers.
> > > > >     * 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.
> > >
> >
> > Hi,
> >
> > The adjusted testcase now fails on aarch64:
> > FAIL:  gfortran.dg/vect/vect-8.f90   -O   scan-tree-dump-times vect
> > "vectorized 23 loops" 1
>
> That likely means it needs adjustment for the aarch64 case as well
> which I didn't touch.  I suppose it's now vectorizing 24 loops?
> And 24 with SVE as well, so we might be able to merge the
> aarch64_sve and aarch64 && ! aarch64_sve cases?
>
> Like with
>
> diff --git a/gcc/testsuite/gfortran.dg/vect/vect-8.f90
> b/gcc/testsuite/gfortran.dg/vect/vect-8.f90
> index cc1aebfbd84..c8a7d896bac 100644
> --- a/gcc/testsuite/gfortran.dg/vect/vect-8.f90
> +++ b/gcc/testsuite/gfortran.dg/vect/vect-8.f90
> @@ -704,7 +704,6 @@ CALL track('KERNEL  ')
>  RETURN
>  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 24 loops" 1 "vect" {
> target 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*-*-* } } } } }
>
> f951 vect.exp testing with and without -march=armv8.3-a+sve shows
> this might work, but if you can double-check that would be nice.
>
>
Indeed LGTM, thanks


> Richard.
>

Re: [PATCH 1/2] Add emulated gather capability to the vectorizer

[Richard Biener]

On Thu, Aug 5, 2021 at 3:26 PM Christophe Lyon via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> On Thu, Aug 5, 2021 at 11:53 AM Richard Biener <rguenther@suse.de> wrote:
>
> > On Thu, 5 Aug 2021, Christophe Lyon wrote:
> >
> > > On Wed, Aug 4, 2021 at 2:08 PM Richard Biener <rguenther@suse.de> wrote:
> > >
> > > > On Wed, 4 Aug 2021, Richard Sandiford wrote:
> > > >
> > > > > Richard Biener <rguenther@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.
> > > > > >
> > > > > > Bootstrapped and tested on x86_64-unknown-linux-gnu.
> > > > > >
> > > > > > 2021-07-30  Richard Biener  <rguenther@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.
> > > > > >     (vect_analyze_data_refs): Always consider gathers.
> > > > > >     * 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.
> > > >
> > >
> > > Hi,
> > >
> > > The adjusted testcase now fails on aarch64:
> > > FAIL:  gfortran.dg/vect/vect-8.f90   -O   scan-tree-dump-times vect
> > > "vectorized 23 loops" 1
> >
> > That likely means it needs adjustment for the aarch64 case as well
> > which I didn't touch.  I suppose it's now vectorizing 24 loops?
> > And 24 with SVE as well, so we might be able to merge the
> > aarch64_sve and aarch64 && ! aarch64_sve cases?
> >
> > Like with
> >
> > diff --git a/gcc/testsuite/gfortran.dg/vect/vect-8.f90
> > b/gcc/testsuite/gfortran.dg/vect/vect-8.f90
> > index cc1aebfbd84..c8a7d896bac 100644
> > --- a/gcc/testsuite/gfortran.dg/vect/vect-8.f90
> > +++ b/gcc/testsuite/gfortran.dg/vect/vect-8.f90
> > @@ -704,7 +704,6 @@ CALL track('KERNEL  ')
> >  RETURN
> >  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 24 loops" 1 "vect" {
> > target 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*-*-* } } } } }
> >
> > f951 vect.exp testing with and without -march=armv8.3-a+sve shows
> > this might work, but if you can double-check that would be nice.
> >
> >
> Indeed LGTM, thanks

Pushed.

>
> > Richard.
> >