1 files changed, 32 insertions, 0 deletions
diff --git a/lib/popcountsi2.c b/lib/popcountsi2.c
new file mode 100644
index 000000000..68220aef9
--- /dev/null
+++ b/lib/popcountsi2.c
@@ -0,0 +1,32 @@
+//===-- popcountsi2.c - Implement __popcountsi2 ---------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements __popcountsi2 for the compiler_rt library.
+//
+//===----------------------------------------------------------------------===//
+
+#include "int_lib.h"
+
+// Returns: count of 1 bits
+
+si_int
+__popcountsi2(si_int a)
+{
+    su_int x = (su_int)a;
+    x = x - ((x >> 1) & 0x55555555);
+    // Every 2 bits holds the sum of every pair of bits
+    x = ((x >> 2) & 0x33333333) + (x & 0x33333333);
+    // Every 4 bits holds the sum of every 4-set of bits (3 significant bits)
+    x = (x + (x >> 4)) & 0x0F0F0F0F;
+    // Every 8 bits holds the sum of every 8-set of bits (4 significant bits)
+    x = (x + (x >> 16));
+    // The lower 16 bits hold two 8 bit sums (5 significant bits).
+    //    Upper 16 bits are garbage
+    return (x + (x >> 8)) & 0x0000003F;  // (6 significant bits)
+}