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- /* ===-- popcountdi2.c - Implement __popcountdi2 ----------------------------===
- *
- * The LLVM Compiler Infrastructure
- *
- * This file is dual licensed under the MIT and the University of Illinois Open
- * Source Licenses. See LICENSE.TXT for details.
- *
- * ===----------------------------------------------------------------------===
- *
- * This file implements __popcountdi2 for the compiler_rt library.
- *
- * ===----------------------------------------------------------------------===
- */
- #include "int_lib.h"
- /* Returns: count of 1 bits */
- COMPILER_RT_ABI 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) */
- }
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