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Re: [PATCH GCC][10/13]Compute and cache data dependence relation
On Fri, Jun 16, 2017 at 11:03 AM, Richard Biener
<richard.guenther@gmail.com> wrote:
> On Mon, Jun 12, 2017 at 7:03 PM, Bin Cheng <Bin.Cheng@arm.com> wrote:
>> Hi,
>> This patch computes and caches data dependence relation in a hash table
>> so that it can be queried multiple times later for partition dependence
>> check.
>> Bootstrap and test on x86_64 and AArch64. Is it OK?
>
> +/* Vector of data dependence relations. */
> +static vec<ddr_p> *ddrs_vec;
> +
> +/* Hash table for data dependence relation in the loop to be distributed. */
> +static hash_table<ddr_entry_hasher> *ddrs_table;
>
> avoid the extra indirection.
>
> +/* Hashtable entry for data reference relation. */
> +struct ddr_entry
> +{
> + data_reference_p a;
> + data_reference_p b;
> + ddr_p ddr;
> + hashval_t hash;
> +};
> ...
> +/* Hash table equality function for data reference relation. */
> +
> +inline bool
> +ddr_entry_hasher::equal (const ddr_entry *entry1, const ddr_entry *entry2)
> +{
> + return (entry1->hash == entry2->hash
> + && DR_STMT (entry1->a) == DR_STMT (entry2->a)
> + && DR_STMT (entry1->b) == DR_STMT (entry2->b)
> + && operand_equal_p (DR_REF (entry1->a), DR_REF (entry2->a), 0)
> + && operand_equal_p (DR_REF (entry1->b), DR_REF (entry2->b), 0));
> +}
>
> what's the issue with using hash_table <ddr_p> with a custom hasher?
> That is, simply key on the dataref pointers (hash them, compare those
> for equality)?
>
> Your scheme looks too complicated / expensive to me ...
>
> You can drop ddrs_vec needed only for memory removal if you traverse
> the hashtable.
Thanks for reviewing. Patch simplified as suggested. Is it OK?
Thanks,
bin
2017-06-17 Bin Cheng <bin.cheng@arm.com>
* tree-loop-distribution.c (struct ddr_hasher): New.
(ddr_hasher::hash, ::equal, get_data_dependence): New function.
(ddrs_table): New.
(classify_partition): Call get_data_dependence.
(pg_add_dependence_edges): Ditto.
(distribute_loop): Release data dependence hash table.
From 6a3d78078355df492877955b5f00784a795a94d8 Mon Sep 17 00:00:00 2001
From: Bin Cheng <binche01@e108451-lin.cambridge.arm.com>
Date: Fri, 9 Jun 2017 13:02:09 +0100
Subject: [PATCH 09/13] cache-data-dependence-20170608.txt
---
gcc/tree-loop-distribution.c | 97 ++++++++++++++++++++++++++++++++------------
1 file changed, 71 insertions(+), 26 deletions(-)
diff --git a/gcc/tree-loop-distribution.c b/gcc/tree-loop-distribution.c
index 2e5a828..a2e543e 100644
--- a/gcc/tree-loop-distribution.c
+++ b/gcc/tree-loop-distribution.c
@@ -70,6 +70,33 @@ along with GCC; see the file COPYING3. If not see
#define MAX_DATAREFS_NUM \
((unsigned) PARAM_VALUE (PARAM_LOOP_MAX_DATAREFS_FOR_DATADEPS))
+/* Hashtable helpers. */
+
+struct ddr_hasher : nofree_ptr_hash <struct data_dependence_relation>
+{
+ static inline hashval_t hash (const data_dependence_relation *);
+ static inline bool equal (const data_dependence_relation *,
+ const data_dependence_relation *);
+};
+
+/* Hash function for data dependence. */
+
+inline hashval_t
+ddr_hasher::hash (const data_dependence_relation *ddr)
+{
+ return iterative_hash_object (DDR_A (ddr),
+ iterative_hash_object (DDR_B (ddr), 0));
+}
+
+/* Hash table equality function for data dependence. */
+
+inline bool
+ddr_hasher::equal (const data_dependence_relation *ddr1,
+ const data_dependence_relation *ddr2)
+{
+ return (DDR_A (ddr1) == DDR_A (ddr2) && DDR_B (ddr1) == DDR_B (ddr2));
+}
+
/* The loop (nest) to be distributed. */
static vec<loop_p> loop_nest;
@@ -79,6 +106,10 @@ static vec<data_reference_p> datarefs_vec;
/* Store index of data reference in aux field. */
#define DR_INDEX(dr) ((uintptr_t) (dr)->aux)
+/* Hash table for data dependence relation in the loop to be distributed. */
+static hash_table<ddr_hasher> ddrs_table (389);
+
+
/* A Reduced Dependence Graph (RDG) vertex representing a statement. */
struct rdg_vertex
{
@@ -1057,6 +1088,32 @@ generate_code_for_partition (struct loop *loop,
return false;
}
+/* Return data dependence relation for data references A and B. The two
+ data references must be in lexicographic order wrto reduced dependence
+ graph RDG. We firstly try to find ddr from global ddr hash table. If
+ it doesn't exist, compute the ddr and cache it. */
+
+static data_dependence_relation *
+get_data_dependence (struct graph *rdg, data_reference_p a, data_reference_p b)
+{
+ struct data_dependence_relation ent, **slot;
+ struct data_dependence_relation *ddr;
+
+ gcc_assert (DR_IS_WRITE (a) || DR_IS_WRITE (b));
+ gcc_assert (rdg_vertex_for_stmt (rdg, DR_STMT (a))
+ <= rdg_vertex_for_stmt (rdg, DR_STMT (b)));
+ ent.a = a;
+ ent.b = b;
+ slot = ddrs_table.find_slot (&ent, INSERT);
+ if (*slot == NULL)
+ {
+ ddr = initialize_data_dependence_relation (a, b, loop_nest);
+ compute_affine_dependence (ddr, loop_nest[0]);
+ *slot = ddr;
+ }
+
+ return *slot;
+}
/* Returns a partition with all the statements needed for computing
the vertex V of the RDG, also including the loop exit conditions. */
@@ -1223,44 +1280,27 @@ classify_partition (loop_p loop, struct graph *rdg, partition *partition)
return;
/* Now check that if there is a dependence this dependence is
of a suitable form for memmove. */
- vec<loop_p> loops = vNULL;
- ddr_p ddr;
- loops.safe_push (loop);
- ddr = initialize_data_dependence_relation (single_load, single_store,
- loops);
- compute_affine_dependence (ddr, loop);
+ ddr_p ddr = get_data_dependence (rdg, single_load, single_store);
if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know)
- {
- free_dependence_relation (ddr);
- loops.release ();
- return;
- }
+ return;
+
if (DDR_ARE_DEPENDENT (ddr) != chrec_known)
{
if (DDR_NUM_DIST_VECTS (ddr) == 0)
- {
- free_dependence_relation (ddr);
- loops.release ();
- return;
- }
+ return;
+
lambda_vector dist_v;
FOR_EACH_VEC_ELT (DDR_DIST_VECTS (ddr), i, dist_v)
{
int dist = dist_v[index_in_loop_nest (loop->num,
DDR_LOOP_NEST (ddr))];
if (dist > 0 && !DDR_REVERSED_P (ddr))
- {
- free_dependence_relation (ddr);
- loops.release ();
- return;
- }
+ return;
}
partition->kind = PKIND_MEMMOVE;
}
else
partition->kind = PKIND_MEMCPY;
- free_dependence_relation (ddr);
- loops.release ();
partition->main_dr = single_store;
partition->secondary_dr = single_load;
partition->niter = nb_iter;
@@ -1474,8 +1514,7 @@ pg_add_dependence_edges (struct graph *rdg, int dir,
std::swap (dr1, dr2);
this_dir = -this_dir;
}
- ddr = initialize_data_dependence_relation (dr1, dr2, loop_nest);
- compute_affine_dependence (ddr, loop_nest[0]);
+ ddr = get_data_dependence (rdg, dr1, dr2);
if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know)
this_dir = 2;
else if (DDR_ARE_DEPENDENT (ddr) == NULL_TREE)
@@ -1501,7 +1540,6 @@ pg_add_dependence_edges (struct graph *rdg, int dir,
}
else
this_dir = 0;
- free_dependence_relation (ddr);
if (this_dir == 2)
return 2;
else if (dir == 0)
@@ -1764,6 +1802,13 @@ distribute_loop (struct loop *loop, vec<gimple *> stmts,
ldist_done:
loop_nest.release ();
free_data_refs (datarefs_vec);
+ for (hash_table<ddr_hasher>::iterator iter = ddrs_table.begin ();
+ iter != ddrs_table.end (); ++iter)
+ {
+ free_dependence_relation (*iter);
+ *iter = NULL;
+ }
+ ddrs_table.empty ();
FOR_EACH_VEC_ELT (partitions, i, partition)
partition_free (partition);
--
1.9.1