* 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.

1 files changed, 15 insertions, 11 deletions

diff --git a/src/alloc.c b/src/alloc.c
index 0a7fda6815c..56a9763db15 100644
--- 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;
 }