* alloc.c (Fmake_string): For ASCII char initializer, prefer

memset to explicit loop.  Otherwise copy largest possible chunk
from initialized to uninitialized part, thus allowing the longer
memcpy runs and reducing the number of loop iterations.

diff --git a/src/ChangeLog b/src/ChangeLog
index 07af64ab1a1175a0fc0b149b8239937cdb25f0eb..4be64c13993c7734f971208bc92266f78027ef3d 100644 (file)
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,10 @@
+2013-10-07  Dmitry Antipov  <dmantipov@yandex.ru>
+
+       * alloc.c (Fmake_string): For ASCII char initializer, prefer
+       memset to explicit loop.  Otherwise copy largest possible chunk
+       from initialized to uninitialized part, thus allowing the longer
+       memcpy runs and reducing the number of loop iterations.
+
 2013-10-06  Jan Djärv  <jan.h.d@swipnet.se>
 
        * nsterm.m (ns_update_begin): If native fullscreen and no toolbar,

diff --git a/src/alloc.c b/src/alloc.c
index 0a7fda6815cc4141aa283df674d272ffb5bbbbc8..56a9763db153b3f9878f99383edbd7804d91e143 100644 (file)
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -1973,7 +1973,6 @@ INIT must be an integer that represents a character.  */)
   (Lisp_Object length, Lisp_Object init)
 {
   register Lisp_Object val;
-  register unsigned char *p, *end;
   int c;
   EMACS_INT nbytes;
 
@@ -1985,31 +1984,36 @@ INIT must be an integer that represents a character.  */)
     {
       nbytes = XINT (length);
       val = make_uninit_string (nbytes);
-      p = SDATA (val);
-      end = p + SCHARS (val);
-      while (p != end)
-       *p++ = c;
+      memset (SDATA (val), c, nbytes);
+      SDATA (val)[nbytes] = 0;
     }
   else
     {
       unsigned char str[MAX_MULTIBYTE_LENGTH];
       int len = CHAR_STRING (c, str);
       EMACS_INT string_len = XINT (length);
+      unsigned char *p, *beg, *end;
 
       if (string_len > STRING_BYTES_MAX / len)
        string_overflow ();
       nbytes = len * string_len;
       val = make_uninit_multibyte_string (string_len, nbytes);
-      p = SDATA (val);
-      end = p + nbytes;
-      while (p != end)
+      for (beg = SDATA (val), p = beg, end = beg + nbytes; p < end; p += len)
        {
-         memcpy (p, str, len);
-         p += len;
+         /* First time we just copy `str' to the data of `val'.  */
+         if (p == beg)
+           memcpy (p, str, len);
+         else
+           {
+             /* Next time we copy largest possible chunk from
+                initialized to uninitialized part of `val'.  */
+             len = min (p - beg, end - p);
+             memcpy (p, beg, len);
+           }
        }
+      *p = 0;
     }
 
-  *p = 0;
   return val;
 }