awk: assorted optimizations

hash_find(): do not caclculate hash twice. Do not divide - can use
cheap multiply-by-8 shift.

nextword(): do not repeatedly increment in-memory value, do it in register,
then store final result.

hashwalk_init(): do not strlen() twice.

function                                             old     new   delta
hash_search3                                           -      49     +49
hash_find                                            259     281     +22
nextword                                              19      16      -3
evaluate                                            3141    3137      -4
hash_search                                           54      28     -26
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 1/3 up/down: 71/-33)             Total: 38 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 17 insertions, 9 deletions

diff --git a/editors/awk.c b/editors/awk.c
index 4e29b28cf..a4cd3cf93 100644
--- a/editors/awk.c
+++ b/editors/awk.c
@@ -696,6 +696,7 @@ static void hash_clear(xhash *hash)
                 while (hi) {
                         thi = hi;
                         hi = hi->next;
+//FIXME: this assumes that it's a hash of *variables*:
                         free(thi->data.v.string);
                         free(thi);
                 }
@@ -714,11 +715,11 @@ static void hash_free(xhash *hash)
 #endif
 
 /* find item in hash, return ptr to data, NULL if not found */
-static void *hash_search(xhash *hash, const char *name)
+static NOINLINE void *hash_search3(xhash *hash, const char *name, unsigned idx)
 {
         hash_item *hi;
 
-        hi = hash->items[hashidx(name) % hash->csize];
+        hi = hash->items[idx % hash->csize];
         while (hi) {
                 if (strcmp(hi->name, name) == 0)
                         return &hi->data;
@@ -727,6 +728,11 @@ static void *hash_search(xhash *hash, const char *name)
         return NULL;
 }
 
+static void *hash_search(xhash *hash, const char *name)
+{
+        return hash_search3(hash, name, hashidx(name));
+}
+
 /* grow hash if it becomes too big */
 static void hash_rebuild(xhash *hash)
 {
@@ -762,16 +768,17 @@ static void *hash_find(xhash *hash, const char *name)
         unsigned idx;
         int l;
 
-        hi = hash_search(hash, name);
+        idx = hashidx(name);
+        hi = hash_search3(hash, name, idx);
         if (!hi) {
-                if (++hash->nel / hash->csize > 10)
+                if (++hash->nel > hash->csize * 8)
                         hash_rebuild(hash);
 
                 l = strlen(name) + 1;
                 hi = xzalloc(sizeof(*hi) + l);
                 strcpy(hi->name, name);
 
-                idx = hashidx(name) % hash->csize;
+                idx = idx % hash->csize;
                 hi->next = hash->items[idx];
                 hash->items[idx] = hi;
                 hash->glen += l;
@@ -822,8 +829,10 @@ static char *skip_spaces(char *p)
 static char *nextword(char **s)
 {
         char *p = *s;
-        while (*(*s)++ != '\0')
+        char *q = p;
+        while (*q++ != '\0')
                 continue;
+        *s = q;
         return p;
 }
 
@@ -2116,8 +2125,7 @@ static void hashwalk_init(var *v, xhash *array)
         for (i = 0; i < array->csize; i++) {
                 hi = array->items[i];
                 while (hi) {
-                        strcpy(w->end, hi->name);
-                        nextword(&w->end);
+                        w->end = stpcpy(w->end, hi->name) + 1;
                         hi = hi->next;
                 }
         }
@@ -3504,7 +3512,7 @@ int awk_main(int argc UNUSED_PARAM, char **argv)
                 setari_u(intvar[ARGV], ++i, *argv++);
         setvar_i(intvar[ARGC], i + 1);
 
-        //fdhash = ahash - done via define
+        //fdhash = ahash; // done via define
         newfile("/dev/stdin")->F = stdin;
         newfile("/dev/stdout")->F = stdout;
         newfile("/dev/stderr")->F = stderr;