reftable: use a pointer for pq_entry param

The speed of the merged_iter_pqueue_add() can be improved by using a
pointer to the pq_entry struct, which is 96 bytes. Since the pq_entry
param is worked directly on the stack and does not currently have a
pointer to it, the merged_iter_pqueue_add() function is slightly
slower.

References to pq_entry in reftable have typically included pointers,
such as both of the params for pq_less().

Since we are working with pointers in the pq_entry param, as keenly
pointed out, the pq_entry param has also been made into a const since
the contents of the pq_entry param are copied and not manipulated.

Signed-off-by: Elijah Conners <business@elijahpepe.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

reftable/merged.c

@@ -36,7 +36,7 @@ static int merged_iter_init(struct merged_iter *mi)
 				.rec = rec,
 				.index = i,
 			};
-			merged_iter_pqueue_add(&mi->pq, e);
+			merged_iter_pqueue_add(&mi->pq, &e);
 		}
 	}
 
@@ -71,7 +71,7 @@ static int merged_iter_advance_nonnull_subiter(struct merged_iter *mi,
 		return 0;
 	}
 
-	merged_iter_pqueue_add(&mi->pq, e);
+	merged_iter_pqueue_add(&mi->pq, &e);
 	return 0;
 }
 

reftable/pq.c

@@ -71,7 +71,7 @@ struct pq_entry merged_iter_pqueue_remove(struct merged_iter_pqueue *pq)
 	return e;
 }
 
-void merged_iter_pqueue_add(struct merged_iter_pqueue *pq, struct pq_entry e)
+void merged_iter_pqueue_add(struct merged_iter_pqueue *pq, const struct pq_entry *e)
 {
 	int i = 0;
 
@@ -81,7 +81,7 @@ void merged_iter_pqueue_add(struct merged_iter_pqueue *pq, struct pq_entry e)
 					    pq->cap * sizeof(struct pq_entry));
 	}
 
-	pq->heap[pq->len++] = e;
+	pq->heap[pq->len++] = *e;
 	i = pq->len - 1;
 	while (i > 0) {
 		int j = (i - 1) / 2;

reftable/pq.h

@@ -26,7 +26,7 @@ struct pq_entry merged_iter_pqueue_top(struct merged_iter_pqueue pq);
 int merged_iter_pqueue_is_empty(struct merged_iter_pqueue pq);
 void merged_iter_pqueue_check(struct merged_iter_pqueue pq);
 struct pq_entry merged_iter_pqueue_remove(struct merged_iter_pqueue *pq);
-void merged_iter_pqueue_add(struct merged_iter_pqueue *pq, struct pq_entry e);
+void merged_iter_pqueue_add(struct merged_iter_pqueue *pq, const struct pq_entry *e);
 void merged_iter_pqueue_release(struct merged_iter_pqueue *pq);
 int pq_less(struct pq_entry *a, struct pq_entry *b);
 

reftable/pq_test.c

@@ -46,7 +46,7 @@ static void test_pq(void)
 					       .u.ref = {
 						       .refname = names[i],
 					       } } };
-		merged_iter_pqueue_add(&pq, e);
+		merged_iter_pqueue_add(&pq, &e);
 		merged_iter_pqueue_check(pq);
 		i = (i * 7) % N;
 	} while (i != 1);