Ping
Richard Sandiford <richard.sandif...@linaro.org> writes:
> This patch checks whether two data references x and y cannot
> partially overlap and so are independent whenever &x != &y.
> We can then use this in the vectoriser to optimise alias checks.
>
> Tested on aarch64-linux-gnu and x86_64-linux-gnu. OK to install?
>
> Thanks,
> Richard
>
>
> gcc/
> 2016-05-03 Richard Sandiford <richard.sandif...@linaro.org>
>
> * hash-traits.h (pair_hash): New struct.
> * tree-data-ref.h (data_dependence_relation): Add object_a and
> object_b fields.
> (DDR_OBJECT_A, DDR_OBJECT_B): New macros.
> * tree-data-ref.c (initialize_data_dependence_relation): Initialize
> DDR_OBJECT_A and DDR_OBJECT_B.
> * tree-vectorizer.h (vec_object_pair): New type.
> (_loop_vec_info): Add a check_unequal_addrs field.
> (LOOP_VINFO_CHECK_UNEQUAL_ADDRS): New macro.
> (LOOP_REQUIRES_VERSIONING_FOR_ALIAS): Return true if there is an
> entry in check_unequal_addrs. Check comp_alias_ddrs instead of
> may_alias_ddrs.
> * tree-vect-loop.c (destroy_loop_vec_info): Release
> LOOP_VINFO_CHECK_UNEQUAL_ADDRS.
> (vect_analyze_loop_2): Likewise, when restarting.
> (vect_estimate_min_profitable_iters): Estimate the cost of
> LOOP_VINFO_CHECK_UNEQUAL_ADDRS.
> * tree-vect-data-refs.c: Include tree-hash-traits.h.
> (vect_prune_runtime_alias_test_list): Try to handle conflicts
> using LOOP_VINFO_CHECK_UNEQUAL_ADDRS, if the data dependence allows.
> Count such tests in the final summary.
> * tree-vect-loop-manip.c (chain_cond_expr): New function.
> (vect_create_cond_for_align_checks): Use it.
> (vect_create_cond_for_alias_checks): Likewise.
> (vect_create_cond_for_unequal_addrs): New function.
> (vect_loop_versioning): Call it.
>
> gcc/testsuite/
> * gcc.dg/vect/vect-alias-check-6.c: New test.
>
> Index: gcc/hash-traits.h
> ===================================================================
> --- gcc/hash-traits.h 2017-02-23 19:54:15.000000000 +0000
> +++ gcc/hash-traits.h 2017-05-03 08:48:53.312035228 +0100
> @@ -301,6 +301,76 @@ struct ggc_cache_ptr_hash : pointer_hash
>
> struct nofree_string_hash : string_hash, typed_noop_remove <const char *> {};
>
> +/* Traits for pairs of values, using the first to record empty and
> + deleted slots. */
> +
> +template <typename T1, typename T2>
> +struct pair_hash
> +{
> + typedef std::pair <typename T1::value_type,
> + typename T2::value_type> value_type;
> + typedef std::pair <typename T1::compare_type,
> + typename T2::compare_type> compare_type;
> +
> + static inline hashval_t hash (const value_type &);
> + static inline bool equal (const value_type &, const compare_type &);
> + static inline void remove (value_type &);
> + static inline void mark_deleted (value_type &);
> + static inline void mark_empty (value_type &);
> + static inline bool is_deleted (const value_type &);
> + static inline bool is_empty (const value_type &);
> +};
> +
> +template <typename T1, typename T2>
> +inline hashval_t
> +pair_hash <T1, T2>::hash (const value_type &x)
> +{
> + return iterative_hash_hashval_t (T1::hash (x.first), T2::hash (x.second));
> +}
> +
> +template <typename T1, typename T2>
> +inline bool
> +pair_hash <T1, T2>::equal (const value_type &x, const compare_type &y)
> +{
> + return T1::equal (x.first, y.first) && T2::equal (x.second, y.second);
> +}
> +
> +template <typename T1, typename T2>
> +inline void
> +pair_hash <T1, T2>::remove (value_type &x)
> +{
> + T1::remove (x.first);
> + T2::remove (x.second);
> +}
> +
> +template <typename T1, typename T2>
> +inline void
> +pair_hash <T1, T2>::mark_deleted (value_type &x)
> +{
> + T1::mark_deleted (x.first);
> +}
> +
> +template <typename T1, typename T2>
> +inline void
> +pair_hash <T1, T2>::mark_empty (value_type &x)
> +{
> + T1::mark_empty (x.first);
> +}
> +
> +template <typename T1, typename T2>
> +inline bool
> +pair_hash <T1, T2>::is_deleted (const value_type &x)
> +{
> + return T1::is_deleted (x.first);
> +}
> +
> +template <typename T1, typename T2>
> +inline bool
> +pair_hash <T1, T2>::is_empty (const value_type &x)
> +{
> + return T1::is_empty (x.first);
> +}
> +
> template <typename T> struct default_hash_traits : T {};
>
> template <typename T>
> Index: gcc/tree-data-ref.h
> ===================================================================
> --- gcc/tree-data-ref.h 2017-05-03 08:48:48.737038502 +0100
> +++ gcc/tree-data-ref.h 2017-05-03 08:48:53.313041828 +0100
> @@ -240,6 +240,13 @@ struct data_dependence_relation
> but the analyzer cannot be more specific. */
> tree are_dependent;
>
> + /* If nonnull, COULD_BE_INDEPENDENT_P is true and the accesses are
> + independent when the runtime addresses of OBJECT_A and OBJECT_B
> + are different. The addresses of both objects are invariant in the
> + loop nest. */
> + tree object_a;
> + tree object_b;
> +
> /* For each subscript in the dependence test, there is an element in
> this array. This is the attribute that labels the edge A->B of
> the data_dependence_relation. */
> @@ -303,6 +310,8 @@ #define DDR_A(DDR) (DDR)->a
> #define DDR_B(DDR) (DDR)->b
> #define DDR_AFFINE_P(DDR) (DDR)->affine_p
> #define DDR_ARE_DEPENDENT(DDR) (DDR)->are_dependent
> +#define DDR_OBJECT_A(DDR) (DDR)->object_a
> +#define DDR_OBJECT_B(DDR) (DDR)->object_b
> #define DDR_SUBSCRIPTS(DDR) (DDR)->subscripts
> #define DDR_SUBSCRIPT(DDR, I) DDR_SUBSCRIPTS (DDR)[I]
> #define DDR_NUM_SUBSCRIPTS(DDR) DDR_SUBSCRIPTS (DDR).length ()
> Index: gcc/tree-data-ref.c
> ===================================================================
> --- gcc/tree-data-ref.c 2017-05-03 08:48:48.737038502 +0100
> +++ gcc/tree-data-ref.c 2017-05-03 08:48:53.313041828 +0100
> @@ -1715,6 +1715,15 @@ initialize_data_dependence_relation (str
> }
>
> DDR_COULD_BE_INDEPENDENT_P (res) = true;
> + if (!loop_nest.exists ()
> + || (object_address_invariant_in_loop_p (loop_nest[0],
> + struct_ref_a)
> + && object_address_invariant_in_loop_p (loop_nest[0],
> + struct_ref_b)))
> + {
> + DDR_OBJECT_A (res) = struct_ref_a;
> + DDR_OBJECT_B (res) = struct_ref_b;
> + }
> }
>
> DDR_AFFINE_P (res) = true;
> Index: gcc/tree-vectorizer.h
> ===================================================================
> --- gcc/tree-vectorizer.h 2017-05-03 08:48:48.738045102 +0100
> +++ gcc/tree-vectorizer.h 2017-05-03 08:48:53.315055028 +0100
> @@ -174,6 +174,10 @@ struct dr_with_seg_len_pair_t
>
>
>
> +/* Describes two objects whose addresses must be unequal for the vectorized
> + loop to be valid. */
> +typedef std::pair<tree, tree> vec_object_pair;
> +
> /* Vectorizer state common between loop and basic-block vectorization. */
> struct vec_info {
> enum { bb, loop } kind;
> @@ -270,6 +274,9 @@ typedef struct _loop_vec_info : public v
> lengths from which the run-time aliasing check is built. */
> vec<dr_with_seg_len_pair_t> comp_alias_ddrs;
>
> + /* Check that the addresses of each pair of objects is unequal. */
> + vec<vec_object_pair> check_unequal_addrs;
> +
> /* Statements in the loop that have data references that are candidates
> for a
> runtime (loop versioning) misalignment check. */
> vec<gimple *> may_misalign_stmts;
> @@ -364,6 +371,7 @@ #define LOOP_VINFO_UNALIGNED_DR(L)
> #define LOOP_VINFO_MAY_MISALIGN_STMTS(L) (L)->may_misalign_stmts
> #define LOOP_VINFO_MAY_ALIAS_DDRS(L) (L)->may_alias_ddrs
> #define LOOP_VINFO_COMP_ALIAS_DDRS(L) (L)->comp_alias_ddrs
> +#define LOOP_VINFO_CHECK_UNEQUAL_ADDRS(L) (L)->check_unequal_addrs
> #define LOOP_VINFO_GROUPED_STORES(L) (L)->grouped_stores
> #define LOOP_VINFO_SLP_INSTANCES(L) (L)->slp_instances
> #define LOOP_VINFO_SLP_UNROLLING_FACTOR(L) (L)->slp_unrolling_factor
> @@ -383,7 +391,8 @@ #define LOOP_VINFO_ORIG_LOOP_INFO(L)
> #define LOOP_REQUIRES_VERSIONING_FOR_ALIGNMENT(L) \
> ((L)->may_misalign_stmts.length () > 0)
> #define LOOP_REQUIRES_VERSIONING_FOR_ALIAS(L) \
> - ((L)->comp_alias_ddrs.length () > 0)
> + ((L)->comp_alias_ddrs.length () > 0 \
> + || (L)->check_unequal_addrs.length () > 0)
> #define LOOP_REQUIRES_VERSIONING_FOR_NITERS(L) \
> (LOOP_VINFO_NITERS_ASSUMPTIONS (L))
> #define LOOP_REQUIRES_VERSIONING(L) \
> Index: gcc/tree-vect-loop.c
> ===================================================================
> --- gcc/tree-vect-loop.c 2017-04-18 19:52:35.059158859 +0100
> +++ gcc/tree-vect-loop.c 2017-05-03 08:48:53.315055028 +0100
> @@ -1275,6 +1275,8 @@ destroy_loop_vec_info (loop_vec_info loo
> destroy_cost_data (LOOP_VINFO_TARGET_COST_DATA (loop_vinfo));
> loop_vinfo->scalar_cost_vec.release ();
>
> + LOOP_VINFO_CHECK_UNEQUAL_ADDRS (loop_vinfo).release ();
> +
> free (loop_vinfo);
> loop->aux = NULL;
> }
> @@ -2299,6 +2301,7 @@ vect_analyze_loop_2 (loop_vec_info loop_
> }
> /* Free optimized alias test DDRS. */
> LOOP_VINFO_COMP_ALIAS_DDRS (loop_vinfo).release ();
> + LOOP_VINFO_CHECK_UNEQUAL_ADDRS (loop_vinfo).release ();
> /* Reset target cost data. */
> destroy_cost_data (LOOP_VINFO_TARGET_COST_DATA (loop_vinfo));
> LOOP_VINFO_TARGET_COST_DATA (loop_vinfo)
> @@ -3261,6 +3264,11 @@ vect_estimate_min_profitable_iters (loop
> unsigned len = LOOP_VINFO_COMP_ALIAS_DDRS (loop_vinfo).length ();
> (void) add_stmt_cost (target_cost_data, len, vector_stmt, NULL, 0,
> vect_prologue);
> + len = LOOP_VINFO_CHECK_UNEQUAL_ADDRS (loop_vinfo).length ();
> + if (len)
> + /* Count LEN - 1 ANDs and LEN comparisons. */
> + (void) add_stmt_cost (target_cost_data, len * 2 - 1, scalar_stmt,
> + NULL, 0, vect_prologue);
> dump_printf (MSG_NOTE,
> "cost model: Adding cost of checks for loop "
> "versioning aliasing.\n");
> Index: gcc/tree-vect-data-refs.c
> ===================================================================
> --- gcc/tree-vect-data-refs.c 2017-05-03 08:48:48.738045102 +0100
> +++ gcc/tree-vect-data-refs.c 2017-05-03 08:48:53.314048428 +0100
> @@ -50,6 +50,7 @@ Software Foundation; either version 3, o
> #include "expr.h"
> #include "builtins.h"
> #include "params.h"
> +#include "tree-hash-traits.h"
>
> /* Return true if load- or store-lanes optab OPTAB is implemented for
> COUNT vectors of type VECTYPE. NAME is the name of OPTAB. */
> @@ -3085,10 +3086,14 @@ dependence_distance_ge_vf (data_dependen
> bool
> vect_prune_runtime_alias_test_list (loop_vec_info loop_vinfo)
> {
> - vec<ddr_p> may_alias_ddrs =
> - LOOP_VINFO_MAY_ALIAS_DDRS (loop_vinfo);
> - vec<dr_with_seg_len_pair_t>& comp_alias_ddrs =
> - LOOP_VINFO_COMP_ALIAS_DDRS (loop_vinfo);
> + typedef pair_hash <tree_operand_hash, tree_operand_hash> tree_pair_hash;
> + hash_set <tree_pair_hash> compared_objects;
> +
> + vec<ddr_p> may_alias_ddrs = LOOP_VINFO_MAY_ALIAS_DDRS (loop_vinfo);
> + vec<dr_with_seg_len_pair_t> &comp_alias_ddrs
> + = LOOP_VINFO_COMP_ALIAS_DDRS (loop_vinfo);
> + vec<vec_object_pair> &check_unequal_addrs
> + = LOOP_VINFO_CHECK_UNEQUAL_ADDRS (loop_vinfo);
> int vect_factor = LOOP_VINFO_VECT_FACTOR (loop_vinfo);
> tree scalar_loop_iters = LOOP_VINFO_NITERS (loop_vinfo);
>
> @@ -3151,6 +3156,24 @@ vect_prune_runtime_alias_test_list (loop
> if (dependence_distance_ge_vf (ddr, loop_depth, vect_factor))
> continue;
>
> + if (DDR_OBJECT_A (ddr))
> + {
> + vec_object_pair new_pair (DDR_OBJECT_A (ddr), DDR_OBJECT_B (ddr));
> + if (!compared_objects.add (new_pair))
> + {
> + if (dump_enabled_p ())
> + {
> + dump_printf_loc (MSG_NOTE, vect_location, "checking that ");
> + dump_generic_expr (MSG_NOTE, TDF_SLIM, new_pair.first);
> + dump_printf (MSG_NOTE, " and ");
> + dump_generic_expr (MSG_NOTE, TDF_SLIM, new_pair.second);
> + dump_printf (MSG_NOTE, " have different addresses\n");
> + }
> + LOOP_VINFO_CHECK_UNEQUAL_ADDRS (loop_vinfo).safe_push (new_pair);
> + }
> + continue;
> + }
> +
> dr_a = DDR_A (ddr);
> stmt_a = DR_STMT (DDR_A (ddr));
> dr_group_first_a = GROUP_FIRST_ELEMENT (vinfo_for_stmt (stmt_a));
> @@ -3346,11 +3369,12 @@ vect_prune_runtime_alias_test_list (loop
> }
> }
>
> + unsigned int count = (comp_alias_ddrs.length ()
> + + check_unequal_addrs.length ());
> dump_printf_loc (MSG_NOTE, vect_location,
> "improved number of alias checks from %d to %d\n",
> - may_alias_ddrs.length (), comp_alias_ddrs.length ());
> - if ((int) comp_alias_ddrs.length () >
> - PARAM_VALUE (PARAM_VECT_MAX_VERSION_FOR_ALIAS_CHECKS))
> + may_alias_ddrs.length (), count);
> + if ((int) count > PARAM_VALUE (PARAM_VECT_MAX_VERSION_FOR_ALIAS_CHECKS))
> {
> if (dump_enabled_p ())
> dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
> Index: gcc/tree-vect-loop-manip.c
> ===================================================================
> --- gcc/tree-vect-loop-manip.c 2017-04-18 19:52:34.027608884 +0100
> +++ gcc/tree-vect-loop-manip.c 2017-05-03 08:48:53.314048428 +0100
> @@ -1926,6 +1926,20 @@ vect_create_cond_for_niters_checks (loop
> *cond_expr = part_cond_expr;
> }
>
> +/* Set *COND_EXPR to a tree that is true when both the original *COND_EXPR
> + and PART_COND_EXPR are true. Treat a null *COND_EXPR as "true". */
> +
> +static void
> +chain_cond_expr (tree *cond_expr, tree part_cond_expr)
> +{
> + if (*cond_expr)
> + *cond_expr = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
> + *cond_expr, part_cond_expr);
> + else
> + *cond_expr = part_cond_expr;
> +}
> +
> +
> /* Function vect_create_cond_for_align_checks.
>
> Create a conditional expression that represents the alignment checks for
> @@ -2037,13 +2051,32 @@ vect_create_cond_for_align_checks (loop_
> ptrsize_zero = build_int_cst (int_ptrsize_type, 0);
> part_cond_expr = fold_build2 (EQ_EXPR, boolean_type_node,
> and_tmp_name, ptrsize_zero);
> - if (*cond_expr)
> - *cond_expr = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
> - *cond_expr, part_cond_expr);
> - else
> - *cond_expr = part_cond_expr;
> + chain_cond_expr (cond_expr, part_cond_expr);
> }
>
> +
> +/* If LOOP_VINFO_CHECK_UNEQUAL_ADDRS contains <A1, B1>, ..., <An, Bn>,
> + create a tree representation of: (&A1 != &B1) && ... && (&An != &Bn).
> + Set *COND_EXPR to a tree that is true when both the original *COND_EXPR
> + and this new condition are true. Treat a null *COND_EXPR as "true". */
> +
> +static void
> +vect_create_cond_for_unequal_addrs (loop_vec_info loop_vinfo, tree
> *cond_expr)
> +{
> + vec<vec_object_pair> pairs = LOOP_VINFO_CHECK_UNEQUAL_ADDRS (loop_vinfo);
> + unsigned int i;
> + vec_object_pair *pair;
> + FOR_EACH_VEC_ELT (pairs, i, pair)
> + {
> + tree addr1 = build_fold_addr_expr (pair->first);
> + tree addr2 = build_fold_addr_expr (pair->second);
> + tree part_cond_expr = fold_build2 (NE_EXPR, boolean_type_node,
> + addr1, addr2);
> + chain_cond_expr (cond_expr, part_cond_expr);
> + }
> +}
> +
> +
> /* Given two data references and segment lengths described by DR_A and DR_B,
> create expression checking if the two addresses ranges intersect with
> each other based on index of the two addresses. This can only be done
> @@ -2280,11 +2313,7 @@ vect_create_cond_for_alias_checks (loop_
>
> /* Create condition expression for each pair data references. */
> create_intersect_range_checks (loop_vinfo, &part_cond_expr, dr_a,
> dr_b);
> - if (*cond_expr)
> - *cond_expr = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
> - *cond_expr, part_cond_expr);
> - else
> - *cond_expr = part_cond_expr;
> + chain_cond_expr (cond_expr, part_cond_expr);
> }
>
> if (dump_enabled_p ())
> @@ -2353,7 +2382,10 @@ vect_loop_versioning (loop_vec_info loop
> &cond_expr_stmt_list);
>
> if (version_alias)
> - vect_create_cond_for_alias_checks (loop_vinfo, &cond_expr);
> + {
> + vect_create_cond_for_unequal_addrs (loop_vinfo, &cond_expr);
> + vect_create_cond_for_alias_checks (loop_vinfo, &cond_expr);
> + }
>
> cond_expr = force_gimple_operand_1 (cond_expr, &gimplify_stmt_list,
> is_gimple_condexpr, NULL_TREE);
> Index: gcc/testsuite/gcc.dg/vect/vect-alias-check-6.c
> ===================================================================
> --- /dev/null 2017-05-03 08:16:26.972699664 +0100
> +++ gcc/testsuite/gcc.dg/vect/vect-alias-check-6.c 2017-05-03
> 08:48:53.312035228 +0100
> @@ -0,0 +1,23 @@
> +/* { dg-do compile } */
> +/* { dg-require-effective-target vect_int } */
> +
> +#define N 16
> +
> +struct s { int x[N]; };
> +
> +void
> +f1 (struct s *a, struct s *b)
> +{
> + for (int i = 0; i < N - 1; ++i)
> + a->x[i + 1] += b->x[i];
> +}
> +
> +void
> +f2 (struct s *a, struct s *b)
> +{
> + for (int i = 0; i < N; ++i)
> + a->x[i] += b->x[N - i - 1];
> +}
> +
> +/* { dg-final { scan-tree-dump-times {checking that [^\n]* and [^\n]* have
> different addresses} 2 "vect" } } */
> +/* { dg-final { scan-tree-dump-times "LOOP VECTORIZED" 2 "vect" } } */
