[cfe-commits] [libcxx] r145684 - /libcxx/trunk/include/support/win32/support.h

[Howard Hinnant]

Author: hhinnant
Date: Fri Dec  2 11:22:38 2011
New Revision: 145684

URL: http://llvm.org/viewvc/llvm-project?rev=145684&view=rev
Log:
Jean-Daniel: __builtin_popcountll support for Windows

Modified:
    libcxx/trunk/include/support/win32/support.h

Modified: libcxx/trunk/include/support/win32/support.h
URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/support/win32/support.h?rev=145684&r1=145683&r2=145684&view=diff
==============================================================================
--- libcxx/trunk/include/support/win32/support.h (original)
+++ libcxx/trunk/include/support/win32/support.h Fri Dec  2 11:22:38 2011
@@ -52,9 +52,32 @@
 
 #ifndef __clang__ // MSVC-based Clang also defines _MSC_VER
 #include <intrin.h>
-#define __builtin_popcount __popcnt
-#define __builtin_popcountl __popcnt
-#define __builtin_popcountll(__i) static_cast<int>(__popcnt64(__i))
+
+_LIBCPP_ALWAYS_INLINE int __builtin_popcount(unsigned int x) {
+   static const unsigned int m1 = 0x55555555; //binary: 0101...
+   static const unsigned int m2 = 0x33333333; //binary: 00110011..
+   static const unsigned int m4 = 0x0f0f0f0f; //binary:  4 zeros,  4 ones ...
+   static const unsigned int h01= 0x01010101; //the sum of 256 to the power of 0,1,2,3...
+   x -= (x >> 1) & m1;             //put count of each 2 bits into those 2 bits
+   x = (x & m2) + ((x >> 2) & m2); //put count of each 4 bits into those 4 bits
+   x = (x + (x >> 4)) & m4;        //put count of each 8 bits into those 8 bits
+   return (x * h01) >> 24;  //returns left 8 bits of x + (x<<8) + (x<<16) + (x<<24)
+}
+
+_LIBCPP_ALWAYS_INLINE int __builtin_popcountl(unsigned long x) {
+  return __builtin_popcount(static_cast<int>(x));
+}
+
+_LIBCPP_ALWAYS_INLINE int __builtin_popcountll(unsigned long long x) {
+   static const unsigned long long m1  = 0x5555555555555555; //binary: 0101...
+   static const unsigned long long m2  = 0x3333333333333333; //binary: 00110011..
+   static const unsigned long long m4  = 0x0f0f0f0f0f0f0f0f; //binary:  4 zeros,  4 ones ...
+   static const unsigned long long h01 = 0x0101010101010101; //the sum of 256 to the power of 0,1,2,3...
+   x -= (x >> 1) & m1;             //put count of each 2 bits into those 2 bits
+   x = (x & m2) + ((x >> 2) & m2); //put count of each 4 bits into those 4 bits
+   x = (x + (x >> 4)) & m4;        //put count of each 8 bits into those 8 bits
+   return static_cast<int>((x * h01)>>56);  //returns left 8 bits of x + (x<<8) + (x<<16) + (x<<24) + ...
+}
 
 _LIBCPP_ALWAYS_INLINE int __builtin_ctz( unsigned int x )
 {