scratch/hash-table-perf ed4ce0af9a9 06/35: Refactor: extract hash and index computations to functions

[Mattias Engdegård]

branch: scratch/hash-table-perf
commit ed4ce0af9a9111cc22561fea19843f5530475861
Author: Mattias Engdegård <mattiase@acm.org>
Commit: Mattias Engdegård <mattiase@acm.org>

    Refactor: extract hash and index computations to functions
    
    * src/lisp.h (hash_from_key):
    * src/fns.c (hash_index_index): New.
    (hash_table_rehash, hash_lookup, hash_remove_from_table):
    (maybe_resize_hash_table, hash_put):
    * src/composite.c (composition_gstring_put_cache): Use them.
---
 src/composite.c |  2 +-
 src/fns.c       | 34 ++++++++++++++++++----------------
 src/lisp.h      |  7 +++++++
 3 files changed, 26 insertions(+), 17 deletions(-)

diff --git a/src/composite.c b/src/composite.c
index aeae02fd1ce..142259acadf 100644
--- a/src/composite.c
+++ b/src/composite.c
@@ -653,7 +653,7 @@ composition_gstring_put_cache (Lisp_Object gstring, 
ptrdiff_t len)
 {
   struct Lisp_Hash_Table *h = XHASH_TABLE (gstring_hash_table);
   Lisp_Object header = LGSTRING_HEADER (gstring);
-  Lisp_Object hash = h->test.hashfn (header, h);
+  Lisp_Object hash = hash_from_key (h, header);
   if (len < 0)
     {
       ptrdiff_t glyph_len = LGSTRING_GLYPH_LEN (gstring);
diff --git a/src/fns.c b/src/fns.c
index e0e52adb77f..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);
          }
@@ -4718,8 +4725,8 @@ hash_table_rehash (Lisp_Object hash)
   for (i = 0; i < count; i++)
     {
       Lisp_Object key = HASH_KEY (h, i);
-      Lisp_Object hash_code = h->test.hashfn (key, h);
-      ptrdiff_t start_of_bucket = XUFIXNUM (hash_code) % ASIZE (h->index);
+      Lisp_Object hash_code = hash_from_key (h, key);
+      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);
@@ -4738,15 +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_code = h->test.hashfn (key, h);
+  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
@@ -4773,14 +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);
@@ -4791,7 +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;
@@ -4803,8 +4805,8 @@ hash_put (struct Lisp_Hash_Table *h, Lisp_Object key, 
Lisp_Object value,
 void
 hash_remove_from_table (struct Lisp_Hash_Table *h, Lisp_Object key)
 {
-  Lisp_Object hash_code = h->test.hashfn (key, h);
-  ptrdiff_t start_of_bucket = XUFIXNUM (hash_code) % ASIZE (h->index);
+  Lisp_Object hash_code = hash_from_key (h, key);
+  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);
diff --git a/src/lisp.h b/src/lisp.h
index c28d52af8b8..863a0fe4a3e 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -2524,6 +2524,13 @@ HASH_TABLE_SIZE (const struct Lisp_Hash_Table *h)
   return size;
 }
 
+/* Compute hash value for KEY in hash table H.  */
+INLINE Lisp_Object
+hash_from_key (struct Lisp_Hash_Table *h, Lisp_Object key)
+{
+  return h->test.hashfn (key, h);
+}
+
 void hash_table_rehash (Lisp_Object);
 
 /* Default size for hash tables if not specified.  */