diff options
author | Daniel Dunbar <daniel@zuster.org> | 2009-06-26 16:47:03 +0000 |
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committer | Daniel Dunbar <daniel@zuster.org> | 2009-06-26 16:47:03 +0000 |
commit | b3a6901e66f55b35aa9e01bcb24134e6a65ea004 (patch) | |
tree | 4d57d73575ea3f7e30bf430920d6e96fa2a369c1 /lib/popcountdi2.c | |
parent | 8cbe163cba77c772621f89ddb33793ac170b1fa2 (diff) |
Initial import of compiler-rt.
-
git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@74292 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/popcountdi2.c')
-rw-r--r-- | lib/popcountdi2.c | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/lib/popcountdi2.c b/lib/popcountdi2.c new file mode 100644 index 000000000..338bbb3ca --- /dev/null +++ b/lib/popcountdi2.c @@ -0,0 +1,35 @@ +//===-- popcountdi2.c - Implement __popcountdi2 ----------------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file implements __popcountdi2 for the compiler_rt library. +// +//===----------------------------------------------------------------------===// + +#include "int_lib.h" + +// Returns: count of 1 bits + +si_int +__popcountdi2(di_int a) +{ + du_int x2 = (du_int)a; + x2 = x2 - ((x2 >> 1) & 0x5555555555555555uLL); + // Every 2 bits holds the sum of every pair of bits (32) + x2 = ((x2 >> 2) & 0x3333333333333333uLL) + (x2 & 0x3333333333333333uLL); + // Every 4 bits holds the sum of every 4-set of bits (3 significant bits) (16) + x2 = (x2 + (x2 >> 4)) & 0x0F0F0F0F0F0F0F0FuLL; + // Every 8 bits holds the sum of every 8-set of bits (4 significant bits) (8) + su_int x = (su_int)(x2 + (x2 >> 32)); + // The lower 32 bits hold four 16 bit sums (5 significant bits). + // Upper 32 bits are garbage + x = x + (x >> 16); + // The lower 16 bits hold two 32 bit sums (6 significant bits). + // Upper 16 bits are garbage + return (x + (x >> 8)) & 0x0000007F; // (7 significant bits) +} |