nobu	2016-12-25 17:47:22 +0900 (Sun, 25 Dec 2016)

  New Revision: 57179

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=57179

  Log:
    bignum.c: precise fdiv
    
    * bignum.c (big_fdiv): more precise calculation.  [ruby-dev:49915]

  Modified files:
    trunk/bignum.c
Index: bignum.c
===================================================================
--- bignum.c	(revision 57178)
+++ bignum.c	(revision 57179)
@@ -6102,6 +6102,8 @@ big_fdiv(VALUE x, VALUE y, long ey) https://github.com/ruby/ruby/blob/trunk/bignum.c#L6102
     l = BIGNUM_LEN(x);
     ex = l * BITSPERDIG - nlz(BDIGITS(x)[l-1]);
     ex -= 2 * DBL_BIGDIG * BITSPERDIG;
+    if (ex > BITSPERDIG) ex -= BITSPERDIG;
+    else if (ex > 0) ex = 0;
     if (ex) x = big_shift(x, ex);
 
     bigdivrem(x, y, &z, 0);

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