optimize FIXABLE macro

Looking at the source code, FIXABLE tends to be just before LOING2FIX
to check applicability of that operation.  Why not try computing first
then check for overflow, which should be optimial.

I also tried the same thing for unsigned types but resulted in slower
execution.  It seems RB_POSFIXABLE() is fast enough on modern CPUs.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57789 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 31 insertions, 6 deletions

diff --git a/include/ruby/ruby.h b/include/ruby/ruby.h
index d770c30735..0cd88fb002 100644
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -1504,6 +1504,29 @@ rb_integer_type_p(VALUE obj)
 }
 #endif
 
+static inline int
+rb_long2fix_overflow(long l, VALUE *ptr)
+{
+#ifdef HAVE_BUILTIN___BUILTIN_MUL_OVERFLOW
+    SIGNED_VALUE v;
+    if (__builtin_mul_overflow(l, 2, &v)) {
+	return 1;
+    }
+    else {
+	*ptr = ((VALUE)v) | RUBY_FIXNUM_FLAG;
+	return 0;
+    }
+#else
+    if (RB_FIXABLE(l)) {
+	*ptr = RB_LONG2FIX(l);
+	return 0;
+    }
+    else {
+	return 1;
+    }
+#endif
+}
+
 #if SIZEOF_INT < SIZEOF_LONG
 # define RB_INT2NUM(v) RB_INT2FIX((int)(v))
 # define RB_UINT2NUM(v) RB_LONG2FIX((unsigned int)(v))
@@ -1511,10 +1534,11 @@ rb_integer_type_p(VALUE obj)
 static inline VALUE
 rb_int2num_inline(int v)
 {
-    if (RB_FIXABLE(v))
-	return RB_INT2FIX(v);
-    else
+    VALUE ret;
+    if (rb_long2fix_overflow(v, &ret))
 	return rb_int2big(v);
+    else
+	return ret;
 }
 #define RB_INT2NUM(x) rb_int2num_inline(x)
 
@@ -1534,10 +1558,11 @@ rb_uint2num_inline(unsigned int v)
 static inline VALUE
 rb_long2num_inline(long v)
 {
-    if (RB_FIXABLE(v))
-	return RB_LONG2FIX(v);
-    else
+    VALUE ret;
+    if (rb_long2fix_overflow(v, &ret))
 	return rb_int2big(v);
+    else
+	return ret;
 }
 #define RB_LONG2NUM(x) rb_long2num_inline(x)