On Mon, Jul 3, 2017 at 9:35 AM, Richard Sandiford
<richard.sandif...@linaro.org> wrote:
> A later patch adds base alignment information to innermost_loop_behavior.
> After that, the only remaining piece of alignment information that wasn't
> immediately obvious was the step alignment. Adding that allows a minor
> simplification to vect_compute_data_ref_alignment, and also potentially
> improves the handling of variable strides for outer loop vectorisation.
> A later patch will also use it to give the alignment of the DR as a whole.
>
> Tested on aarch64-linux-gnu and x86_64-linux-gnu. OK to install?
Ok.
> Richard
>
>
> 2017-07-03 Richard Sandiford <richard.sandif...@linaro.org>
>
> gcc/
> * tree-data-ref.h (innermost_loop_behavior): Add a step_alignment
> field.
> (DR_STEP_ALIGNMENT): New macro.
> * tree-vectorizer.h (STMT_VINFO_DR_STEP_ALIGNMENT): Likewise.
> * tree-data-ref.c (dr_analyze_innermost): Initalize step_alignment.
> (create_data_ref): Print it.
> * tree-vect-stmts.c (vectorizable_load): Use the step alignment
> to tell whether the step preserves vector (mis)alignment.
> * tree-vect-data-refs.c (vect_compute_data_ref_alignment): Likewise.
> Move the check for an integer step and generalise to all INTEGER_CST.
> (vect_analyze_data_refs): Set DR_STEP_ALIGNMENT when setting DR_STEP.
> Print the outer step alignment.
>
> Index: gcc/tree-data-ref.h
> ===================================================================
> --- gcc/tree-data-ref.h 2017-07-03 07:51:31.005161213 +0100
> +++ gcc/tree-data-ref.h 2017-07-03 07:52:14.194782203 +0100
> @@ -56,6 +56,9 @@ struct innermost_loop_behavior
> high value if the offset is zero. This is a byte rather than a bit
> quantity. */
> unsigned int offset_alignment;
> +
> + /* Likewise for STEP. */
> + unsigned int step_alignment;
> };
>
> /* Describes the evolutions of indices of the memory reference. The indices
> @@ -145,6 +148,7 @@ #define DR_INIT(DR) (DR)-
> #define DR_STEP(DR) (DR)->innermost.step
> #define DR_PTR_INFO(DR) (DR)->alias.ptr_info
> #define DR_OFFSET_ALIGNMENT(DR) (DR)->innermost.offset_alignment
> +#define DR_STEP_ALIGNMENT(DR) (DR)->innermost.step_alignment
> #define DR_INNERMOST(DR) (DR)->innermost
>
> typedef struct data_reference *data_reference_p;
> Index: gcc/tree-vectorizer.h
> ===================================================================
> --- gcc/tree-vectorizer.h 2017-07-03 07:51:31.006161241 +0100
> +++ gcc/tree-vectorizer.h 2017-07-03 07:52:14.196782157 +0100
> @@ -709,6 +709,8 @@ #define STMT_VINFO_DR_OFFSET(S)
> #define STMT_VINFO_DR_STEP(S) (S)->dr_wrt_vec_loop.step
> #define STMT_VINFO_DR_OFFSET_ALIGNMENT(S) \
> (S)->dr_wrt_vec_loop.offset_alignment
> +#define STMT_VINFO_DR_STEP_ALIGNMENT(S) \
> + (S)->dr_wrt_vec_loop.step_alignment
>
> #define STMT_VINFO_IN_PATTERN_P(S) (S)->in_pattern_p
> #define STMT_VINFO_RELATED_STMT(S) (S)->related_stmt
> Index: gcc/tree-data-ref.c
> ===================================================================
> --- gcc/tree-data-ref.c 2017-07-03 07:51:31.004161185 +0100
> +++ gcc/tree-data-ref.c 2017-07-03 07:52:14.193782226 +0100
> @@ -870,6 +870,7 @@ dr_analyze_innermost (struct data_refere
> drb->init = init;
> drb->step = step;
> drb->offset_alignment = highest_pow2_factor (offset_iv.base);
> + drb->step_alignment = highest_pow2_factor (step);
>
> if (dump_file && (dump_flags & TDF_DETAILS))
> fprintf (dump_file, "success.\n");
> @@ -1085,6 +1086,7 @@ create_data_ref (loop_p nest, loop_p loo
> print_generic_expr (dump_file, DR_STEP (dr), TDF_SLIM);
> fprintf (dump_file, "\n\toffset alignment: %d",
> DR_OFFSET_ALIGNMENT (dr));
> + fprintf (dump_file, "\n\tstep alignment: %d", DR_STEP_ALIGNMENT (dr));
> fprintf (dump_file, "\n\tbase_object: ");
> print_generic_expr (dump_file, DR_BASE_OBJECT (dr), TDF_SLIM);
> fprintf (dump_file, "\n");
> Index: gcc/tree-vect-stmts.c
> ===================================================================
> --- gcc/tree-vect-stmts.c 2017-07-03 07:51:05.480852682 +0100
> +++ gcc/tree-vect-stmts.c 2017-07-03 07:52:14.195782180 +0100
> @@ -7294,8 +7294,7 @@ vectorizable_load (gimple *stmt, gimple_
> nested within an outer-loop that is being vectorized. */
>
> if (nested_in_vect_loop
> - && (TREE_INT_CST_LOW (DR_STEP (dr))
> - % GET_MODE_SIZE (TYPE_MODE (vectype)) != 0))
> + && (DR_STEP_ALIGNMENT (dr) % GET_MODE_SIZE (TYPE_MODE (vectype))) != 0)
> {
> gcc_assert (alignment_support_scheme != dr_explicit_realign_optimized);
> compute_in_loop = true;
> Index: gcc/tree-vect-data-refs.c
> ===================================================================
> --- gcc/tree-vect-data-refs.c 2017-07-03 07:51:31.006161241 +0100
> +++ gcc/tree-vect-data-refs.c 2017-07-03 07:52:14.194782203 +0100
> @@ -698,10 +698,9 @@ vect_compute_data_ref_alignment (struct
> divides by the vector size. */
> else if (nested_in_vect_loop_p (loop, stmt))
> {
> - tree step = DR_STEP (dr);
> step_preserves_misalignment_p
> - = (tree_fits_shwi_p (step)
> - && tree_to_shwi (step) % GET_MODE_SIZE (TYPE_MODE (vectype)) == 0);
> + = (DR_STEP_ALIGNMENT (dr)
> + % GET_MODE_SIZE (TYPE_MODE (vectype))) == 0;
>
> if (dump_enabled_p ())
> {
> @@ -720,12 +719,10 @@ vect_compute_data_ref_alignment (struct
> the dataref evenly divides by the vector size. */
> else
> {
> - tree step = DR_STEP (dr);
> unsigned vf = LOOP_VINFO_VECT_FACTOR (loop_vinfo);
> step_preserves_misalignment_p
> - = (tree_fits_shwi_p (step)
> - && ((tree_to_shwi (step) * vf)
> - % GET_MODE_SIZE (TYPE_MODE (vectype)) == 0));
> + = ((DR_STEP_ALIGNMENT (dr) * vf)
> + % GET_MODE_SIZE (TYPE_MODE (vectype))) == 0;
>
> if (!step_preserves_misalignment_p && dump_enabled_p ())
> dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
> @@ -773,7 +770,10 @@ vect_compute_data_ref_alignment (struct
> alignment = TYPE_ALIGN_UNIT (vectype);
>
> if (drb->offset_alignment < alignment
> - || !step_preserves_misalignment_p)
> + || !step_preserves_misalignment_p
> + /* We need to know whether the step wrt the vectorized loop is
> + negative when computing the starting misalignment below. */
> + || TREE_CODE (drb->step) != INTEGER_CST)
> {
> if (dump_enabled_p ())
> {
> @@ -3414,6 +3414,8 @@ vect_analyze_data_refs (vec_info *vinfo,
> DR_STEP (newdr) = step;
> DR_OFFSET_ALIGNMENT (newdr)
> = BIGGEST_ALIGNMENT;
> + DR_STEP_ALIGNMENT (newdr)
> + = highest_pow2_factor (step);
> dr = newdr;
> simd_lane_access = true;
> }
> @@ -3665,6 +3667,8 @@ vect_analyze_data_refs (vec_info *vinfo,
> STMT_VINFO_DR_STEP (stmt_info));
> dump_printf (MSG_NOTE, "\n\touter offset alignment: %d\n",
> STMT_VINFO_DR_OFFSET_ALIGNMENT (stmt_info));
> + dump_printf (MSG_NOTE, "\n\touter step alignment: %d\n",
> + STMT_VINFO_DR_STEP_ALIGNMENT (stmt_info));
> }
> }
>
