With the increase in the number of modes and patterns for some
backend architectures, the place_operands function becomes a
bottleneck in the speed of genoutput, and may even become a
bottleneck in 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 | 101 ++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 95 insertions(+), 6 deletions(-)
diff --git a/gcc/genoutput.cc b/gcc/genoutput.cc
index efd81766bb5b..456d96112cfb 100644
--- a/gcc/genoutput.cc
+++ b/gcc/genoutput.cc
@@ -112,6 +112,8 @@ 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;
@@ -127,11 +129,12 @@ 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;
static struct operand_data **odata_end = &null_operand.next;
+static htab_t operand_data_table;
/* Must match the constants in recog.h. */
@@ -180,6 +183,11 @@ static void place_operands (class data *);
static void process_template (class data *, const char *);
static void validate_insn_alternatives (class data *);
static void validate_insn_operands (class data *);
+static hashval_t hash_struct_operand_data (const void *);
+static int eq_struct_operand_data (const void *, const void *);
+static void insert_operand_data (struct operand_data *);
+static struct operand_data *lookup_operand_data (struct operand_data *);
+static void init_operand_data_table (void);
class constraint_data
{
@@ -532,6 +540,13 @@ 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 +565,6 @@ 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;
@@ -577,9 +589,9 @@ place_operands (class data *d)
return;
}
+ od = lookup_operand_data (&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]))
+ for (i = 0; od; od = od->eq_next, i = 0)
{
od2 = od->next;
i = 1;
@@ -605,6 +617,7 @@ place_operands (class data *d)
*odata_end = od2;
odata_end = &od2->next;
od2->index = next_operand_number++;
+ insert_operand_data (od2);
}
*odata_end = NULL;
return;
@@ -1049,6 +1062,7 @@ main (int argc, const char **argv)
progname = "genoutput";
init_insn_for_nothing ();
+ init_operand_data_table ();
if (!init_rtx_reader_args (argc, argv))
return (FATAL_EXIT_CODE);
@@ -1224,3 +1238,78 @@ mdep_constraint_len (const char *s, file_location loc,
int opno)
message_at (loc, "note: in operand %d", opno);
return 1; /* safe */
}
+
+/* Helper to Hash a struct operand_data. */
+
+static hashval_t
+hash_struct_operand_data (const void *ptr)
+{
+ const struct operand_data *d = (const struct operand_data *) ptr;
+ const char *pred, *cons;
+ hashval_t hash;
+
+ pred = d->predicate;
+ if (!pred)
+ pred = "";
+ hash = htab_hash_string (pred);
+
+ cons = d->constraint;
+ if (!cons)
+ cons = "";
+ hash = iterative_hash (cons, strlen (cons), hash);
+
+ hash = iterative_hash_object (d->mode, hash);
+ hash = iterative_hash_object (d->strict_low, hash);
+ hash = iterative_hash_object (d->eliminable, hash);
+ return hash;
+}
+
+/* Equality function of the operand_data hash table. */
+
+static int
+eq_struct_operand_data (const void *p1, const void *p2)
+{
+ const struct operand_data *d1 = (const struct operand_data *) p1;
+ const struct operand_data *d2 = (const struct operand_data *) p2;
+
+ return compare_operands (const_cast<operand_data *>(d1),
+ const_cast<operand_data *>(d2));
+}
+
+/* Insert the operand_data variable D 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. */
+
+static void
+insert_operand_data (struct operand_data *d)
+{
+ void **slot = htab_find_slot (operand_data_table, d, INSERT);
+ if (*slot)
+ {
+ struct operand_data *last = (struct operand_data *) *slot;
+ while (last->eq_next)
+ last = last->eq_next;
+ last->eq_next = d;
+ }
+ else
+ *slot = d;
+}
+
+/* Look up the operand_data D in the hash table. */
+
+static struct operand_data *
+lookup_operand_data (struct operand_data *d)
+{
+ return (struct operand_data *) htab_find (operand_data_table, d);
+}
+
+/* Initializes the operand_data hash table. */
+
+static void
+init_operand_data_table (void)
+{
+ operand_data_table = htab_create_alloc (64, hash_struct_operand_data,
+ eq_struct_operand_data, 0,
+ xcalloc, free);
+}
--
2.43.0
