diff options
Diffstat (limited to 'compiler-rt/lib/builtins/popcountti2.c')
| -rw-r--r-- | compiler-rt/lib/builtins/popcountti2.c | 50 |
1 files changed, 23 insertions, 27 deletions
diff --git a/compiler-rt/lib/builtins/popcountti2.c b/compiler-rt/lib/builtins/popcountti2.c index 087e3807e46..853fd722309 100644 --- a/compiler-rt/lib/builtins/popcountti2.c +++ b/compiler-rt/lib/builtins/popcountti2.c @@ -1,47 +1,43 @@ -/* ===-- popcountti2.c - Implement __popcountti2 ----------------------------=== - * - * 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 __popcountti2 for the compiler_rt library. - * - * ===----------------------------------------------------------------------=== - */ +//===-- popcountti2.c - Implement __popcountti2 +//----------------------------===// +// +// 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 __popcountti2 for the compiler_rt library. +// +//===----------------------------------------------------------------------===// #include "int_lib.h" #ifdef CRT_HAS_128BIT -/* Returns: count of 1 bits */ +// Returns: count of 1 bits COMPILER_RT_ABI si_int __popcountti2(ti_int a) { tu_int x3 = (tu_int)a; x3 = x3 - ((x3 >> 1) & (((tu_int)0x5555555555555555uLL << 64) | 0x5555555555555555uLL)); - /* Every 2 bits holds the sum of every pair of bits (64) */ + // Every 2 bits holds the sum of every pair of bits (64) x3 = ((x3 >> 2) & (((tu_int)0x3333333333333333uLL << 64) | 0x3333333333333333uLL)) + (x3 & (((tu_int)0x3333333333333333uLL << 64) | 0x3333333333333333uLL)); - /* Every 4 bits holds the sum of every 4-set of bits (3 significant bits) (32) - */ + // Every 4 bits holds the sum of every 4-set of bits (3 significant bits) (32) x3 = (x3 + (x3 >> 4)) & (((tu_int)0x0F0F0F0F0F0F0F0FuLL << 64) | 0x0F0F0F0F0F0F0F0FuLL); - /* Every 8 bits holds the sum of every 8-set of bits (4 significant bits) (16) - */ + // Every 8 bits holds the sum of every 8-set of bits (4 significant bits) (16) du_int x2 = (du_int)(x3 + (x3 >> 64)); - /* Every 8 bits holds the sum of every 8-set of bits (5 significant bits) (8) - */ + // Every 8 bits holds the sum of every 8-set of bits (5 significant bits) (8) su_int x = (su_int)(x2 + (x2 >> 32)); - /* Every 8 bits holds the sum of every 8-set of bits (6 significant bits) (4) - */ + // Every 8 bits holds the sum of every 8-set of bits (6 significant bits) (4) x = x + (x >> 16); - /* Every 8 bits holds the sum of every 8-set of bits (7 significant bits) (2) - */ - /* Upper 16 bits are garbage */ - return (x + (x >> 8)) & 0xFF; /* (8 significant bits) */ + // Every 8 bits holds the sum of every 8-set of bits (7 significant bits) (2) + // + // Upper 16 bits are garbage + return (x + (x >> 8)) & 0xFF; // (8 significant bits) } -#endif /* CRT_HAS_128BIT */ +#endif // CRT_HAS_128BIT |
