libcpp - tiny speedup

["Nicola Pero" <nicola dot pero at meta-innovation dot com>]

This patch inlines a libcpp hash function for speed.  The speedup is to tiny (I had to
run 100m get_identifier() calls in a loop to measure an 8% reduction in time) that I'm
not sure it's worth the extra complication of having a static inline function in the headers.

Anyway since I've already done the work, here it is.  If the libcpp maintainers 
like it I can commit it.  If not, I won't be offended - I was going to trash it anyway. ;-)

Thanks

PS: calc_hash was already automatically inlined by the compiler even if not declared 
inline.  I inlined the other call, which the compiler doesn't do automatically probably
because the function to inline is too big.

Index: symtab.c
===================================================================
--- symtab.c    (revision 165822)
+++ symtab.c    (working copy)
@@ -30,27 +30,12 @@
    intrinsically how to calculate a hash value, and how to compare an
    existing entry with a potential new one.  */
 
-static unsigned int calc_hash (const unsigned char *, size_t);
 static void ht_expand (hash_table *);
 static double approx_sqrt (double);
 
 /* A deleted entry.  */
 #define DELETED ((hashnode) -1)
 
-/* Calculate the hash of the string STR of length LEN.  */
-
-static unsigned int
-calc_hash (const unsigned char *str, size_t len)
-{
-  size_t n = len;
-  unsigned int r = 0;
-
-  while (n--)
-    r = HT_HASHSTEP (r, *str++);
-
-  return HT_HASHFINISH (r, len);
-}
-
 /* Initialize an identifier hashtable.  */
 
 hash_table *
@@ -85,20 +70,7 @@
   free (table);
 }
 
-/* Returns the hash entry for the a STR of length LEN.  If that string
-   already exists in the table, returns the existing entry.  If the
-   identifier hasn't been seen before, and INSERT is CPP_NO_INSERT,
-   returns NULL.  Otherwise insert and returns a new entry.  A new
-   string is allocated.  */
 hashnode
-ht_lookup (hash_table *table, const unsigned char *str, size_t len,
-          enum ht_lookup_option insert)
-{
-  return ht_lookup_with_hash (table, str, len, calc_hash (str, len),
-                             insert);
-}
-
-hashnode
 ht_lookup_with_hash (hash_table *table, const unsigned char *str,
                     size_t len, unsigned int hash,
                     enum ht_lookup_option insert)
Index: include/symtab.h
===================================================================
--- include/symtab.h    (revision 165822)
+++ include/symtab.h    (working copy)
@@ -76,14 +76,34 @@
 /* Frees all memory associated with a hash table.  */
 extern void ht_destroy (hash_table *);
 
-extern hashnode ht_lookup (hash_table *, const unsigned char *,
-                          size_t, enum ht_lookup_option);
 extern hashnode ht_lookup_with_hash (hash_table *, const unsigned char *,
                                      size_t, unsigned int,
                                      enum ht_lookup_option);
+
 #define HT_HASHSTEP(r, c) ((r) * 67 + ((c) - 113));
 #define HT_HASHFINISH(r, len) ((r) + (len))
 
+/* Returns the hash entry for the a STR of length LEN.  If that string
+   already exists in the table, returns the existing entry.  If the
+   identifier hasn't been seen before, and INSERT is CPP_NO_INSERT,
+   returns NULL.  Otherwise insert and returns a new entry.  A new
+   string is allocated.  */
+static inline hashnode
+ht_lookup (hash_table *table, const unsigned char *str, size_t len,
+          enum ht_lookup_option insert)
+{
+  /* Calculate the hash of the string STR of length LEN.  */
+  size_t n = len;
+  unsigned int r = 0;
+  const unsigned char *s = str;
+
+  while (n--)
+    r = HT_HASHSTEP (r, *s++);
+
+  return ht_lookup_with_hash (table, str, len, HT_HASHFINISH (r, len),
+                             insert);
+}
+
 /* For all nodes in TABLE, make a callback.  The callback takes
    TABLE->PFILE, the node, and a PTR, and the callback sequence stops
    if the callback returns zero.  */

Index: ChangeLog
===================================================================
--- ChangeLog   (revision 165822)
+++ ChangeLog   (working copy)
@@ -1,3 +1,9 @@
+2010-10-22  Nicola Pero <nicola.pero@meta-innovation.com>
+
+       * include/symtab.h (ht_lookup): Added as static inline.
+       * symtab.c (calc_hash): Removed.
+       (ht_lookup): Removed.
+       
 2010-10-19  Basile Starynkevitch  <basile@starynkevitch.net>
        * line-map.h (source_location): Remove obsolete comment
        mentioning location_s.