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Re: [PATCH GCC][10/13]Compute and cache data dependence relation


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.

Richard.

> Thanks,
> bin
>
> 2017-06-07  Bin Cheng  <bin.cheng@arm.com>
>
>         * tree-loop-distribution.c (struct ddr_entry, ddr_entry_hasher): New.
>         (ddr_entry_hasher::hash, ::equal, get_data_dependence): New function.
>         (ddrs_vec, ddrs_table): New.
>         (classify_partition): Call get_data_dependence.
>         (pg_add_dependence_edges): Ditto.
>         (distribute_loop): Initialize data dependence global variables.


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