diff options
Diffstat (limited to 'compiler-rt/lib/builtins/clzsi2.c')
| -rw-r--r-- | compiler-rt/lib/builtins/clzsi2.c | 74 |
1 files changed, 36 insertions, 38 deletions
diff --git a/compiler-rt/lib/builtins/clzsi2.c b/compiler-rt/lib/builtins/clzsi2.c index 90dc82d08ef..3f9f27f4133 100644 --- a/compiler-rt/lib/builtins/clzsi2.c +++ b/compiler-rt/lib/builtins/clzsi2.c @@ -1,50 +1,48 @@ -/* ===-- clzsi2.c - Implement __clzsi2 -------------------------------------=== - * - * 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 __clzsi2 for the compiler_rt library. - * - * ===----------------------------------------------------------------------=== - */ +//===-- clzsi2.c - Implement __clzsi2 -------------------------------------===// +// +// 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 __clzsi2 for the compiler_rt library. +// +//===----------------------------------------------------------------------===// #include "int_lib.h" -/* Returns: the number of leading 0-bits */ +// Returns: the number of leading 0-bits -/* Precondition: a != 0 */ +// Precondition: a != 0 COMPILER_RT_ABI si_int __clzsi2(si_int a) { su_int x = (su_int)a; - si_int t = ((x & 0xFFFF0000) == 0) << 4; /* if (x is small) t = 16 else 0 */ - x >>= 16 - t; /* x = [0 - 0xFFFF] */ - su_int r = t; /* r = [0, 16] */ - /* return r + clz(x) */ + si_int t = ((x & 0xFFFF0000) == 0) << 4; // if (x is small) t = 16 else 0 + x >>= 16 - t; // x = [0 - 0xFFFF] + su_int r = t; // r = [0, 16] + // return r + clz(x) t = ((x & 0xFF00) == 0) << 3; - x >>= 8 - t; /* x = [0 - 0xFF] */ - r += t; /* r = [0, 8, 16, 24] */ - /* return r + clz(x) */ + x >>= 8 - t; // x = [0 - 0xFF] + r += t; // r = [0, 8, 16, 24] + // return r + clz(x) t = ((x & 0xF0) == 0) << 2; - x >>= 4 - t; /* x = [0 - 0xF] */ - r += t; /* r = [0, 4, 8, 12, 16, 20, 24, 28] */ - /* return r + clz(x) */ + x >>= 4 - t; // x = [0 - 0xF] + r += t; // r = [0, 4, 8, 12, 16, 20, 24, 28] + // return r + clz(x) t = ((x & 0xC) == 0) << 1; - x >>= 2 - t; /* x = [0 - 3] */ - r += t; /* r = [0 - 30] and is even */ - /* return r + clz(x) */ - /* switch (x) - * { - * case 0: - * return r + 2; - * case 1: - * return r + 1; - * case 2: - * case 3: - * return r; - * } - */ + x >>= 2 - t; // x = [0 - 3] + r += t; // r = [0 - 30] and is even + // return r + clz(x) + // switch (x) + // { + // case 0: + // return r + 2; + // case 1: + // return r + 1; + // case 2: + // case 3: + // return r; + // } return r + ((2 - x) & -((x & 2) == 0)); } |
