forked from OSchip/llvm-project
40 lines
1.4 KiB
C
40 lines
1.4 KiB
C
/* ===-- ctzdi2.c - Implement __ctzdi2 -------------------------------------===
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*
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* Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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* See https://llvm.org/LICENSE.txt for license information.
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* SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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*
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* ===----------------------------------------------------------------------===
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*
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* This file implements __ctzdi2 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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/* Returns: the number of trailing 0-bits */
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#if !defined(__clang__) && \
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((defined(__sparc__) && defined(__arch64__)) || \
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defined(__mips64) || \
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(defined(__riscv) && __SIZEOF_POINTER__ >= 8))
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/* On 64-bit architectures with neither a native clz instruction nor a native
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* ctz instruction, gcc resolves __builtin_ctz to __ctzdi2 rather than
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* __ctzsi2, leading to infinite recursion. */
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#define __builtin_ctz(a) __ctzsi2(a)
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extern si_int __ctzsi2(si_int);
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#endif
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/* Precondition: a != 0 */
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COMPILER_RT_ABI si_int
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__ctzdi2(di_int a)
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{
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dwords x;
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x.all = a;
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const si_int f = -(x.s.low == 0);
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return __builtin_ctz((x.s.high & f) | (x.s.low & ~f)) +
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(f & ((si_int)(sizeof(si_int) * CHAR_BIT)));
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}
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