* bignum.c (bary_mul): x*1 is x.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41869 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,7 @@
+Wed Jul 10 00:41:42 2013  Tanaka Akira  <akr@fsij.org>
+
+	* bignum.c (bary_mul): x*1 is x.
+
 Tue Jul  9 22:24:39 2013  Tanaka Akira  <akr@fsij.org>
 
 	* bignum.c (bary_mul1): No need to invoke MEMZERO at last.

bignum.c

@@ -1856,6 +1856,17 @@ bary_mul(BDIGIT *zds, size_t zl, BDIGIT *xds, size_t xl, BDIGIT *yds, size_t yl,
         return;
     }
 
+    if (xl == 1 && xds[0] == 1) {
+        MEMCPY(zds, yds, BDIGIT, yl);
+        MEMZERO(zds + yl, BDIGIT, zl - yl);
+        return;
+    }
+    if (yl == 1 && yds[0] == 1) {
+        MEMCPY(zds, xds, BDIGIT, xl);
+        MEMZERO(zds + xl, BDIGIT, zl - xl);
+        return;
+    }
+
     /* normal multiplication when x is small */
     if (xl < KARATSUBA_MUL_DIGITS) {
       normal: