45 lines
1.7 KiB
C
45 lines
1.7 KiB
C
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/* ===-- popcountti2.c - Implement __popcountti2 ----------------------------===
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*
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* The LLVM Compiler Infrastructure
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*
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* This file is dual licensed under the MIT and the University of Illinois Open
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* Source Licenses. See LICENSE.TXT for details.
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*
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* ===----------------------------------------------------------------------===
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*
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* This file implements __popcountti2 for the compiler_rt library.
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*
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* ===----------------------------------------------------------------------===
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*/
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#include "int_lib.h"
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#if __x86_64
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/* Returns: count of 1 bits */
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si_int
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__popcountti2(ti_int a)
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{
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tu_int x3 = (tu_int)a;
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x3 = x3 - ((x3 >> 1) & (((tu_int)0x5555555555555555uLL << 64) |
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0x5555555555555555uLL));
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/* Every 2 bits holds the sum of every pair of bits (64) */
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x3 = ((x3 >> 2) & (((tu_int)0x3333333333333333uLL << 64) | 0x3333333333333333uLL))
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+ (x3 & (((tu_int)0x3333333333333333uLL << 64) | 0x3333333333333333uLL));
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/* Every 4 bits holds the sum of every 4-set of bits (3 significant bits) (32) */
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x3 = (x3 + (x3 >> 4))
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& (((tu_int)0x0F0F0F0F0F0F0F0FuLL << 64) | 0x0F0F0F0F0F0F0F0FuLL);
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/* Every 8 bits holds the sum of every 8-set of bits (4 significant bits) (16) */
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du_int x2 = (du_int)(x3 + (x3 >> 64));
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/* Every 8 bits holds the sum of every 8-set of bits (5 significant bits) (8) */
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su_int x = (su_int)(x2 + (x2 >> 32));
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/* Every 8 bits holds the sum of every 8-set of bits (6 significant bits) (4) */
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x = x + (x >> 16);
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/* Every 8 bits holds the sum of every 8-set of bits (7 significant bits) (2) */
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/* Upper 16 bits are garbage */
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return (x + (x >> 8)) & 0xFF; /* (8 significant bits) */
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}
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#endif
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