scratch/hash-table-perf 3d2042c48a6 07/37: Refactor: extract hash index computation to a function

[Mattias Engdegård]

branch: scratch/hash-table-perf
commit 3d2042c48a60c3c4e43fcad06990c5de9e949878
Author: Mattias Engdegård <mattiase@acm.org>
Commit: Mattias Engdegård <mattiase@acm.org>

    Refactor: extract hash index computation to a function
    
    This way we have it in one place instead of five.
    
    * src/fns.c (hash_index_index): New.
    (maybe_resize_hash_table, hash_table_rehash, hash_lookup)
    (hash_put, hash_remove_from_table): Use it.
---
 src/fns.c | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/src/fns.c b/src/fns.c
index 1c6bd4fd526..aeaeea7375f 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -4631,6 +4631,13 @@ copy_hash_table (struct Lisp_Hash_Table *h1)
 }
 
 
+/* Compute index into the index vector from a hash value.  */
+static inline ptrdiff_t
+hash_index_index (struct Lisp_Hash_Table *h, Lisp_Object hash_code)
+{
+  return XUFIXNUM (hash_code) % ASIZE (h->index);
+}
+
 /* Resize hash table H if it's too full.  If H cannot be resized
    because it's already too large, throw an error.  */
 
@@ -4689,8 +4696,8 @@ maybe_resize_hash_table (struct Lisp_Hash_Table *h)
       for (ptrdiff_t i = 0; i < old_size; i++)
        if (!NILP (HASH_HASH (h, i)))
          {
-           EMACS_UINT hash_code = XUFIXNUM (HASH_HASH (h, i));
-           ptrdiff_t start_of_bucket = hash_code % ASIZE (h->index);
+           Lisp_Object hash_code = HASH_HASH (h, i);
+           ptrdiff_t start_of_bucket = hash_index_index (h, hash_code);
            set_hash_next_slot (h, i, HASH_INDEX (h, start_of_bucket));
            set_hash_index_slot (h, start_of_bucket, i);
          }
@@ -4719,7 +4726,7 @@ hash_table_rehash (Lisp_Object hash)
     {
       Lisp_Object key = HASH_KEY (h, i);
       Lisp_Object hash_code = hash_from_key (h, key);
-      ptrdiff_t start_of_bucket = XUFIXNUM (hash_code) % ASIZE (h->index);
+      ptrdiff_t start_of_bucket = hash_index_index (h, hash_code);
       set_hash_hash_slot (h, i, hash_code);
       set_hash_next_slot (h, i, HASH_INDEX (h, start_of_bucket));
       set_hash_index_slot (h, start_of_bucket, i);
@@ -4738,14 +4745,12 @@ hash_table_rehash (Lisp_Object hash)
 ptrdiff_t
 hash_lookup (struct Lisp_Hash_Table *h, Lisp_Object key, Lisp_Object *hash)
 {
-  ptrdiff_t start_of_bucket, i;
-
   Lisp_Object hash_code = hash_from_key (h, key);
   if (hash)
     *hash = hash_code;
 
-  start_of_bucket = XUFIXNUM (hash_code) % ASIZE (h->index);
-
+  ptrdiff_t start_of_bucket = hash_index_index (h, hash_code);
+  ptrdiff_t i;
   for (i = HASH_INDEX (h, start_of_bucket); 0 <= i; i = HASH_NEXT (h, i))
     if (EQ (key, HASH_KEY (h, i))
        || (h->test.cmpfn
@@ -4772,14 +4777,12 @@ ptrdiff_t
 hash_put (struct Lisp_Hash_Table *h, Lisp_Object key, Lisp_Object value,
          Lisp_Object hash)
 {
-  ptrdiff_t start_of_bucket, i;
-
   /* Increment count after resizing because resizing may fail.  */
   maybe_resize_hash_table (h);
   h->count++;
 
   /* Store key/value in the key_and_value vector.  */
-  i = h->next_free;
+  ptrdiff_t i = h->next_free;
   eassert (NILP (HASH_HASH (h, i)));
   eassert (BASE_EQ (Qunbound, (HASH_KEY (h, i))));
   h->next_free = HASH_NEXT (h, i);
@@ -4790,7 +4793,7 @@ hash_put (struct Lisp_Hash_Table *h, Lisp_Object key, 
Lisp_Object value,
   set_hash_hash_slot (h, i, hash);
 
   /* Add new entry to its collision chain.  */
-  start_of_bucket = XUFIXNUM (hash) % ASIZE (h->index);
+  ptrdiff_t start_of_bucket = hash_index_index (h, hash);
   set_hash_next_slot (h, i, HASH_INDEX (h, start_of_bucket));
   set_hash_index_slot (h, start_of_bucket, i);
   return i;
@@ -4803,7 +4806,7 @@ void
 hash_remove_from_table (struct Lisp_Hash_Table *h, Lisp_Object key)
 {
   Lisp_Object hash_code = hash_from_key (h, key);
-  ptrdiff_t start_of_bucket = XUFIXNUM (hash_code) % ASIZE (h->index);
+  ptrdiff_t start_of_bucket = hash_index_index (h, hash_code);
   ptrdiff_t prev = -1;
 
   for (ptrdiff_t i = HASH_INDEX (h, start_of_bucket);