* bignum.c (bary_divmod): Add special cases for x < y easily detected

  and nx == 2 && ny == 2.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42139 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

2 files changed, 23 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index 326604c94e..a37eabd251 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Jul 23 20:14:55 2013  Tanaka Akira  <akr@fsij.org>
+
+	* bignum.c (bary_divmod): Add special cases for x < y easily detected
+	  and nx == 2 && ny == 2.
+
 Tue Jul 23 19:48:38 2013  Koichi Sasada  <ko1@atdot.net>
 
 	* thread_(pthread|win32).h: rename rb_thread_cond_t to
diff --git a/bignum.c b/bignum.c
index 820be62158..e1d7a6d871 100644
--- a/bignum.c
+++ b/bignum.c
@@ -5266,12 +5266,29 @@ bary_divmod(BDIGIT *qds, size_t nq, BDIGIT *rds, size_t nr, BDIGIT *xds, size_t
         return;
     }
 
-    if (ny == 1) {
+    if (nx < ny || (nx == ny && xds[nx - 1] < yds[ny - 1])) {
+        MEMCPY(rds, xds, BDIGIT, nx);
+        BDIGITS_ZERO(rds+nx, nr-nx);
+        BDIGITS_ZERO(qds, nq);
+    }
+    else if (ny == 1) {
         MEMCPY(qds, xds, BDIGIT, nx);
         BDIGITS_ZERO(qds+nx, nq-nx);
         rds[0] = bigdivrem_single(qds, xds, nx, yds[0]);
         BDIGITS_ZERO(rds+1, nr-1);
     }
+    else if (nx == 2 && ny == 2) {
+        BDIGIT_DBL x = xds[0] | BIGUP(xds[1]);
+        BDIGIT_DBL y = yds[0] | BIGUP(yds[1]);
+        BDIGIT_DBL q = x / y;
+        BDIGIT_DBL r = x % y;
+        qds[0] = BIGLO(q);
+        qds[1] = BIGLO(BIGDN(q));
+        BDIGITS_ZERO(qds+2, nq-2);
+        rds[0] = BIGLO(r);
+        rds[1] = BIGLO(BIGDN(r));
+        BDIGITS_ZERO(rds+2, nr-2);
+    }
     else {
         int extra_words;
         long j;