[mono/mono] fd7cec89: [sgen] Use gcc bitcount intrinsics where appropriate.

   Branch: refs/heads/master
     Home: https://github.com/mono/mono
  Compare: https://github.com/mono/mono/compare/8f604d71f13f...fd7cec894df1

   Commit: fd7cec894df1a7fc157c8b47212eab67f241e002
   Author: Zoltan Varga <[email protected]> (vargaz)
     Date: 2013-10-04 19:54:17 GMT
      URL: https://github.com/mono/mono/commit/fd7cec894df1a7fc157c8b47212eab67f241e002

[sgen] Use gcc bitcount intrinsics where appropriate.

Changed paths:
  M mono/metadata/sgen-marksweep.c

Modified: mono/metadata/sgen-marksweep.c
===================================================================
@@ -1574,22 +1574,20 @@ struct _MSBlockInfo {
 static inline int
 bitcount (mword d)
 {
-#if SIZEOF_VOID_P == 8
-	/* http://www.jjj.de/bitwizardry/bitwizardrypage.html */
-	d -=  (d>>1) & 0x5555555555555555;
-	d  = ((d>>2) & 0x3333333333333333) + (d & 0x3333333333333333);
-	d  = ((d>>4) + d) & 0x0f0f0f0f0f0f0f0f;
-	d *= 0x0101010101010101;
-	return d >> 56;
+	int count = 0;
+
+#ifdef __GNUC__
+	if (sizeof (mword) == sizeof (unsigned long))
+		count += __builtin_popcountl (d);
+	else
+		count += __builtin_popcount (d);
 #else
-	/* http://aggregate.org/MAGIC/ */
-	d -= ((d >> 1) & 0x55555555);
-	d = (((d >> 2) & 0x33333333) + (d & 0x33333333));
-	d = (((d >> 4) + d) & 0x0f0f0f0f);
-	d += (d >> 8);
-	d += (d >> 16);
-	return (d & 0x0000003f);
+	while (d) {
+		count ++;
+		d &= (d - 1);
+	}
 #endif
+	return count;
 }
 
 static void


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