* include/ruby/ruby.h (rb_float_value): optimize it.

This technique was pointed by shinichiro.hamaji
  <http://shinh.skr.jp/m/?date=20120825#p02>.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@36832 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,9 @@
+Mon Aug 27 18:19:36 2012  Koichi Sasada  <ko1@atdot.net>
+
+	* include/ruby/ruby.h (rb_float_value): optimize it.
+	  This technique was pointed by shinichiro.hamaji
+	  <http://shinh.skr.jp/m/?date=20120825#p02>.
+
 Mon Aug 27 15:08:25 2012  Yuki Yugui Sonoda  <yugui@google.com>
 
 	* common.mk (vm_trace.o): Added a missing dependency.

include/ruby/ruby.h

@@ -733,10 +733,7 @@ static inline double
 rb_float_value(VALUE v)
 {
     if (FLONUM_P(v)) {
-	if (v == (VALUE)0x8000000000000002) {
-	    return 0.0;
-	}
-	else {
+	if (v != (VALUE)0x8000000000000002) { /* LIKELY */
 	    union {
 		double d;
 		VALUE v;
@@ -746,9 +743,12 @@ rb_float_value(VALUE v)
 	    /* e: xx1... -> 011... */
 	    /*    xx0... -> 100... */
 	    /*      ^b63           */
-	    t.v = RUBY_BIT_ROTR(((b63 ^ 1) << 1) | b63 | (v & ~0x03), 3);
+	    t.v = RUBY_BIT_ROTR(2 - b63 | (v & ~0x03), 3);
 	    return t.d;
 	}
+	else {
+	    return 0.0;
+	}
     }
     else {
 	return ((struct RFloat *)v)->float_value;