Robert Clausecker
6296500a85
This new header complies with ISO/IEC 9899:2024 (C23). Contrary to glibc, we do not provide inline definitions in <stdbit.h> as we expect our system compiler to soon recognise these as builtins anyway. Relnotes: yes MFC after: 1 month Reviewed by: adrian Approved by: markj (mentor) Differential Revision: https://reviews.freebsd.org/D53657
61 lines
1.1 KiB
C
61 lines
1.1 KiB
C
/*
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* Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <assert.h>
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#include <limits.h>
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#include <stdbit.h>
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/* Offset must be greater than zero. */
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static_assert(UCHAR_WIDTH < UINT_WIDTH,
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"stdc_leading_zeros_uc needs UCHAR_WIDTH < UINT_WIDTH");
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unsigned int
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stdc_leading_zeros_uc(unsigned char x)
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{
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const int offset = UINT_WIDTH - UCHAR_WIDTH;
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return (__builtin_clz((x << offset) + (1U << (offset - 1))));
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}
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/* Offset must be greater than zero. */
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static_assert(USHRT_WIDTH < UINT_WIDTH,
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"stdc_leading_zeros_us needs USHRT_WIDTH < UINT_WIDTH");
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unsigned int
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stdc_leading_zeros_us(unsigned short x)
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{
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const int offset = UINT_WIDTH - USHRT_WIDTH;
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return (__builtin_clz((x << offset) + (1U << (offset - 1))));
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}
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unsigned int
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stdc_leading_zeros_ui(unsigned int x)
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{
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if (x == 0)
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return (UINT_WIDTH);
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return (__builtin_clz(x));
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}
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unsigned int
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stdc_leading_zeros_ul(unsigned long x)
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{
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if (x == 0)
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return (ULONG_WIDTH);
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return (__builtin_clzl(x));
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}
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unsigned int
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stdc_leading_zeros_ull(unsigned long long x)
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{
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if (x == 0)
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return (ULLONG_WIDTH);
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return (__builtin_clzll(x));
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}
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