naruse	2016-03-14 19:14:48 +0900 (Mon, 14 Mar 2016)

  New Revision: 54102

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=54102

  Log:
    * bignum.c (big2str_2bdigits): reduce div instruction.
    
    Fix the code so that C compiler unify div instructions of `%` and `/`.
    
    Before:
      4291b0:       48 89 f0                mov    %rsi,%rax
      4291b3:       31 d2                   xor    %edx,%edx
      4291b5:       48 83 ef 01             sub    $0x1,%rdi
      4291b9:       48 f7 f1                div    %rcx  # <---- !
      4291bc:       41 0f b6 04 11          movzbl (%r9,%rdx,1),%eax
      4291c1:       31 d2                   xor    %edx,%edx
      4291c3:       41 88 04 38             mov    %al,(%r8,%rdi,1)
      4291c7:       48 63 4b 04             movslq 0x4(%rbx),%rcx
      4291cb:       48 89 f0                mov    %rsi,%rax
      4291ce:       48 f7 f1                div    %rcx  # <---- !
      4291d1:       48 89 c6                mov    %rax,%rsi
      4291d4:       48 85 ff                test   %rdi,%rdi
      4291d7:       75 d7                   jne    4291b0 <big2str_2bdigits+0x50>
      4291d9:       48 63 6b 10             movslq 0x10(%rbx),%rbp
      4291dd:       48 01 6b 20             add    %rbp,0x20(%rbx)
      4291e1:       48 8b 44 24 48          mov    0x48(%rsp),%rax
      4291e6:       64 48 33 04 25 28 00    xor    %fs:0x28,%rax
    
    After:
      4291b0:       48 63 73 04             movslq 0x4(%rbx),%rsi
      4291b4:       31 d2                   xor    %edx,%edx
      4291b6:       48 83 e9 01             sub    $0x1,%rcx
      4291ba:       48 f7 f6                div    %rsi  # <---- !
      4291bd:       41 0f b6 14 10          movzbl (%r8,%rdx,1),%edx
      4291c2:       88 14 0f                mov    %dl,(%rdi,%rcx,1)
      4291c5:       48 85 c9                test   %rcx,%rcx
      4291c8:       75 e6                   jne    4291b0 <big2str_2bdigits+0x50>
      4291ca:       48 63 6b 10             movslq 0x10(%rbx),%rbp
      4291ce:       48 01 6b 20             add    %rbp,0x20(%rbx)
      4291d2:       48 8b 44 24 48          mov    0x48(%rsp),%rax
      4291d7:       64 48 33 04 25 28 00    xor    %fs:0x28,%rax

  Modified files:
    trunk/ChangeLog
    trunk/bignum.c
Index: bignum.c
===================================================================
--- bignum.c	(revision 54101)
+++ bignum.c	(revision 54102)
@@ -4615,8 +4615,9 @@ big2str_2bdigits(struct big2str_struct * https://github.com/ruby/ruby/blob/trunk/bignum.c#L4615
         p = buf;
         j = sizeof(buf);
         do {
-            p[--j] = ruby_digitmap[num % b2s->base];
+            BDIGIT_DBL idx = num % b2s->base;
             num /= b2s->base;
+            p[--j] = ruby_digitmap[idx];
         } while (num);
         len = sizeof(buf) - j;
         big2str_alloc(b2s, len + taillen);
@@ -4626,8 +4627,9 @@ big2str_2bdigits(struct big2str_struct * https://github.com/ruby/ruby/blob/trunk/bignum.c#L4627
         p = b2s->ptr;
         j = b2s->hbase2_numdigits;
         do {
-            p[--j] = ruby_digitmap[num % b2s->base];
+            BDIGIT_DBL idx = num % b2s->base;
             num /= b2s->base;
+            p[--j] = ruby_digitmap[idx];
         } while (j);
         len = b2s->hbase2_numdigits;
     }
Index: ChangeLog
===================================================================
--- ChangeLog	(revision 54101)
+++ ChangeLog	(revision 54102)
@@ -1,3 +1,7 @@ https://github.com/ruby/ruby/blob/trunk/ChangeLog#L1
+Mon Mar 14 19:05:39 2016  NARUSE, Yui  <naruse@r...>
+
+	* bignum.c (big2str_2bdigits): reduce div instruction.
+
 Mon Mar 14 18:39:53 2016  Martin Duerst  <duerst@i...>
 
 	* include/ruby/oniguruma.h, enc/unicode.c: Adjusting flag assignments

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