1 files changed, 43 insertions, 0 deletions
diff --git a/lib/popcountti2.c b/lib/popcountti2.c
new file mode 100644
index 000000000..9ac052d91
--- /dev/null
+++ b/lib/popcountti2.c
@@ -0,0 +1,43 @@
+//===-- popcountti2.c - Implement __popcountti2 ----------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements __popcountti2 for the compiler_rt library.
+//
+//===----------------------------------------------------------------------===//
+
+#if __x86_64
+
+#include "int_lib.h"
+
+// Returns: count of 1 bits
+
+si_int
+__popcountti2(ti_int a)
+{
+    tu_int x3 = (tu_int)a;
+    x3 = x3 - ((x3 >> 1) & (((tu_int)0x5555555555555555uLL << 64) |
+                                     0x5555555555555555uLL));
+    // Every 2 bits holds the sum of every pair of bits (64)
+    x3 = ((x3 >> 2) & (((tu_int)0x3333333333333333uLL << 64) | 0x3333333333333333uLL))
+       + (x3 & (((tu_int)0x3333333333333333uLL << 64) | 0x3333333333333333uLL));
+    // Every 4 bits holds the sum of every 4-set of bits (3 significant bits) (32)
+    x3 = (x3 + (x3 >> 4))
+       & (((tu_int)0x0F0F0F0F0F0F0F0FuLL << 64) | 0x0F0F0F0F0F0F0F0FuLL);
+    // Every 8 bits holds the sum of every 8-set of bits (4 significant bits) (16)
+    du_int x2 = (du_int)(x3 + (x3 >> 64));
+    // Every 8 bits holds the sum of every 8-set of bits (5 significant bits) (8)
+    su_int x = (su_int)(x2 + (x2 >> 32));
+    // Every 8 bits holds the sum of every 8-set of bits (6 significant bits) (4)
+    x = x + (x >> 16);
+    // Every 8 bits holds the sum of every 8-set of bits (7 significant bits) (2)
+    //   Upper 16 bits are garbage
+    return (x + (x >> 8)) & 0xFF;  // (8 significant bits)
+}
+
+#endif