diff options
Diffstat (limited to 'contrib/compiler-rt/lib/popcountsi2.c')
-rw-r--r-- | contrib/compiler-rt/lib/popcountsi2.c | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/contrib/compiler-rt/lib/popcountsi2.c b/contrib/compiler-rt/lib/popcountsi2.c new file mode 100644 index 0000000..4f092ee --- /dev/null +++ b/contrib/compiler-rt/lib/popcountsi2.c @@ -0,0 +1,33 @@ +/* ===-- 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) */ +} |