diff options
Diffstat (limited to 'compiler-rt/lib/builtins/popcountsi2.c')
| -rw-r--r-- | compiler-rt/lib/builtins/popcountsi2.c | 37 |
1 files changed, 18 insertions, 19 deletions
diff --git a/compiler-rt/lib/builtins/popcountsi2.c b/compiler-rt/lib/builtins/popcountsi2.c index 77c1a314537..75e592a778d 100644 --- a/compiler-rt/lib/builtins/popcountsi2.c +++ b/compiler-rt/lib/builtins/popcountsi2.c @@ -1,30 +1,29 @@ -/* ===-- popcountsi2.c - Implement __popcountsi2 ---------------------------=== - * - * 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 __popcountsi2 for the compiler_rt library. - * - * ===----------------------------------------------------------------------=== - */ +//===-- popcountsi2.c - Implement __popcountsi2 ---------------------------===// +// +// 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 __popcountsi2 for the compiler_rt library. +// +//===----------------------------------------------------------------------===// #include "int_lib.h" -/* Returns: count of 1 bits */ +// Returns: count of 1 bits COMPILER_RT_ABI si_int __popcountsi2(si_int a) { su_int x = (su_int)a; x = x - ((x >> 1) & 0x55555555); - /* Every 2 bits holds the sum of every pair of bits */ + // Every 2 bits holds the sum of every pair of bits x = ((x >> 2) & 0x33333333) + (x & 0x33333333); - /* Every 4 bits holds the sum of every 4-set of bits (3 significant bits) */ + // Every 4 bits holds the sum of every 4-set of bits (3 significant bits) x = (x + (x >> 4)) & 0x0F0F0F0F; - /* Every 8 bits holds the sum of every 8-set of bits (4 significant bits) */ + // Every 8 bits holds the sum of every 8-set of bits (4 significant bits) x = (x + (x >> 16)); - /* The lower 16 bits hold two 8 bit sums (5 significant bits).*/ - /* Upper 16 bits are garbage */ - return (x + (x >> 8)) & 0x0000003F; /* (6 significant bits) */ + // The lower 16 bits hold two 8 bit sums (5 significant bits). + // Upper 16 bits are garbage + return (x + (x >> 8)) & 0x0000003F; // (6 significant bits) } |
