With the increase in the number of modes and patterns for some
backend architectures, the place_operands function becomes a
bottleneck int the speed of genoutput, and may even become a
bottleneck int the overall speed of building the GCC project.
This patch aims to accelerate the place_operands function,
the optimizations it includes are:
1. Use a hash table to store operand information,
improving the lookup time for the first operand.
2. Move mode comparison to the beginning to avoid the scenarios of most strcmp.
I tested the speed improvements for the following backends,
Improvement Ratio
x86_64 197.9%
aarch64 954.5%
riscv 2578.6%
If the build machine is slow, then this improvement can save a lot of time.
I tested the genoutput output for x86_64/aarch64/riscv backends,
and there was no difference compared to before the optimization,
so this shouldn't introduce any functional issues.
gcc/
* genoutput.cc (struct operand_data): Add member 'eq_next' to
point to the next member with the same hash value in the
hash table.
(compare_operands): Move the comparison of the mode to the very
beginning to accelerate the comparison of the two operands.
(struct operand_data_hasher): New, a class that takes into account
the necessary elements for comparing the equality of two operands
in its hash value.
(operand_data_hasher::hash): New.
(operand_data_hasher::equal): New.
(operand_datas): New, hash table of konwn pattern operands.
(place_operands): Use a hash table instead of traversing the array
to find the same operand.
(main): Add initialization of the hash table 'operand_datas'.
---
gcc/genoutput.cc | 105 ++++++++++++++++++++++++++++++++++++++---------
1 file changed, 85 insertions(+), 20 deletions(-)
diff --git a/gcc/genoutput.cc b/gcc/genoutput.cc
index efd81766bb5b..cca1b6622d47 100644
--- a/gcc/genoutput.cc
+++ b/gcc/genoutput.cc
@@ -91,6 +91,7 @@ along with GCC; see the file COPYING3. If not see
#include "errors.h"
#include "read-md.h"
#include "gensupport.h"
+#include "hash-table.h"
/* No instruction can have more operands than this. Sorry for this
arbitrary limit, but what machine will have an instruction with
@@ -112,6 +113,8 @@ static int next_operand_number = 1;
struct operand_data
{
struct operand_data *next;
+ /* Point to the next member with the same hash value in the hash table. */
+ struct operand_data *eq_next;
int index;
const char *predicate;
const char *constraint;
@@ -127,7 +130,7 @@ struct operand_data
static struct operand_data null_operand =
{
- 0, 0, "", "", E_VOIDmode, 0, 0, 0, 0, 0
+ 0, 0, 0, "", "", E_VOIDmode, 0, 0, 0, 0, 0
};
static struct operand_data *odata = &null_operand;
@@ -532,6 +535,13 @@ compare_operands (struct operand_data *d0, struct
operand_data *d1)
{
const char *p0, *p1;
+ /* On one hand, comparing strings for predicate and constraint
+ is time-consuming, and on the other hand, the probability of
+ different modes is relatively high. Therefore, checking the mode
+ first can speed up the execution of the program. */
+ if (d0->mode != d1->mode)
+ return 0;
+
p0 = d0->predicate;
if (!p0)
p0 = "";
@@ -550,9 +560,6 @@ compare_operands (struct operand_data *d0, struct
operand_data *d1)
if (strcmp (p0, p1) != 0)
return 0;
- if (d0->mode != d1->mode)
- return 0;
-
if (d0->strict_low != d1->strict_low)
return 0;
@@ -562,6 +569,47 @@ compare_operands (struct operand_data *d0, struct
operand_data *d1)
return 1;
}
+/* This is a class that takes into account the necessary elements for
+ comparing the equality of two operands in its hash value. */
+struct operand_data_hasher : nofree_ptr_hash <operand_data>
+{
+ static inline hashval_t hash (const operand_data *);
+ static inline bool equal (const operand_data *, const operand_data *);
+};
+
+hashval_t
+operand_data_hasher::hash (const operand_data * op_info)
+{
+ inchash::hash h;
+ const char *pred, *cons;
+
+ pred = op_info->predicate;
+ if (!pred)
+ pred = "";
+ h.add (pred, strlen (pred) + 1);
+
+ cons = op_info->constraint;
+ if (!cons)
+ cons = "";
+ h.add (cons, strlen (cons) + 1);
+
+ h.add_object (op_info->mode);
+ h.add_object (op_info->strict_low);
+ h.add_object (op_info->eliminable);
+ return h.end ();
+}
+
+bool
+operand_data_hasher::equal (const operand_data * op_info1,
+ const operand_data * op_info2)
+{
+ return compare_operands (const_cast<operand_data *>(op_info1),
+ const_cast<operand_data *>(op_info2));
+}
+
+/* Hashtable of konwn pattern operands. */
+static hash_table<operand_data_hasher> *operand_datas;
+
/* Scan the list of operands we've already committed to output and either
find a subsequence that is the same, or allocate a new one at the end. */
@@ -569,6 +617,7 @@ static void
place_operands (class data *d)
{
struct operand_data *od, *od2;
+ struct operand_data **slot;
int i;
if (d->n_operands == 0)
@@ -577,23 +626,24 @@ place_operands (class data *d)
return;
}
+ od = operand_datas->find (&d->operand[0]);
/* Brute force substring search. */
- for (od = odata, i = 0; od; od = od->next, i = 0)
- if (compare_operands (od, &d->operand[0]))
- {
- od2 = od->next;
- i = 1;
- while (1)
- {
- if (i == d->n_operands)
- goto full_match;
- if (od2 == NULL)
- goto partial_match;
- if (! compare_operands (od2, &d->operand[i]))
- break;
- ++i, od2 = od2->next;
- }
- }
+ for (; od; od = od->eq_next)
+ {
+ od2 = od->next;
+ i = 1;
+ while (1)
+ {
+ if (i == d->n_operands)
+ goto full_match;
+ if (od2 == NULL)
+ goto partial_match;
+ if (! compare_operands (od2, &d->operand[i]))
+ break;
+ ++i, od2 = od2->next;
+ }
+ }
+ i = 0;
/* Either partial match at the end of the list, or no match. In either
case, we tack on what operands are remaining to the end of the list. */
@@ -605,6 +655,20 @@ place_operands (class data *d)
*odata_end = od2;
odata_end = &od2->next;
od2->index = next_operand_number++;
+ /* Insert the operand_data variable OD2 into the hash table.
+ If an variable with the same hash value already exists in
+ the hash table, insert the element at the end of the
+ linked list connected through the eq_next member. */
+ slot = operand_datas->find_slot (od2, INSERT);
+ if (*slot)
+ {
+ struct operand_data *last = (struct operand_data *) *slot;
+ while (last->eq_next)
+ last = last->eq_next;
+ last->eq_next = od2;
+ }
+ else
+ *slot = od2;
}
*odata_end = NULL;
return;
@@ -1049,6 +1113,7 @@ main (int argc, const char **argv)
progname = "genoutput";
init_insn_for_nothing ();
+ operand_datas = new hash_table<operand_data_hasher> (1024);
if (!init_rtx_reader_args (argc, argv))
return (FATAL_EXIT_CODE);
--
2.43.0
