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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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#ifdef CRT_HAS_128BIT |
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/* Returns: count of 1 bits */ |
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COMPILER_RT_ABI 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 /* CRT_HAS_128BIT */ |