diff options
Diffstat (limited to 'lib/builtins/popcountdi2.c')
| -rw-r--r-- | lib/builtins/popcountdi2.c | 58 | 
1 files changed, 27 insertions, 31 deletions
diff --git a/lib/builtins/popcountdi2.c b/lib/builtins/popcountdi2.c index 5e8a62f075eb9..9bbc39c6608a1 100644 --- a/lib/builtins/popcountdi2.c +++ b/lib/builtins/popcountdi2.c @@ -1,36 +1,32 @@ -/* ===-- 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. - * - * ===----------------------------------------------------------------------=== - */ +//===-- popcountdi2.c - Implement __popcountdi2 ---------------------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// This file implements __popcountdi2 for the compiler_rt library. +// +//===----------------------------------------------------------------------===//  #include "int_lib.h" -/* Returns: count of 1 bits */ +// 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) */ +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)  }  | 
