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23ce05f906
SPDX is an international standard for documenting software license requirements. Remove the existing headers and replace with a brief SPDX preamble. See: https://spdx.dev/use/specifications/ The script used to convert the files is added to "tools", and the file header templates in headers/ are updated. Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
172 lines
3.5 KiB
C
172 lines
3.5 KiB
C
/* SPDX-License-Identifier: BSD-2-Clause */
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/* Copyright 1996-2025 The NASM Authors - All Rights Reserved */
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/*
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* ilog2_xx(x) = x ? floor(log_2(x)) : 0
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*/
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#ifndef NASM_ILOG2_H
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#define NASM_ILOG2_H
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#include "compiler.h"
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#ifdef ILOG2_C /* For generating the out-of-line functions */
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# undef extern_inline
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# define extern_inline
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# define inline_prototypes
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#endif
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#ifdef inline_prototypes
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extern unsigned int const_func ilog2_32(uint32_t v);
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extern unsigned int const_func ilog2_64(uint64_t v);
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extern int const_func alignlog2_32(uint32_t v);
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extern int const_func alignlog2_64(uint64_t v);
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#endif
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#ifdef extern_inline
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# define ROUND(v, a, w) \
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do { \
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if (v & (((UINT32_C(1) << w) - 1) << w)) { \
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a += w; \
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v >>= w; \
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} \
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} while (0)
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# define static_nz(x) (is_constant(x != 0) && (x != 0))
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# define defang_zero(x) ((x) | !static_nz(x))
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# if defined(HAVE_STDC_LEADING_ZEROS)
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extern_inline unsigned int const_func ilog2_32(uint32_t v)
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{
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return stdc_leading_zeros(defang_zero(v)) ^ 31;
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}
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extern_inline unsigned int const_func ilog2_64(uint64_t v)
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{
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return stdc_leading_zeros(defang_zero(v)) ^ 63;
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}
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# else
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# if defined(HAVE___BUILTIN_CLZ) && INT_MAX == 2147483647
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extern_inline unsigned int const_func ilog2_32(uint32_t v)
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{
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return __builtin_clz(v|1) ^ 31;
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}
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# elif defined(__GNUC__) && (defined(__x86_64__) || defined(__i386__))
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extern_inline unsigned int const_func ilog2_32(uint32_t v)
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{
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unsigned int n;
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# ifdef __x86_64__
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__asm__("bsrl %1,%0"
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: "=r" (n)
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: "rm" (v), "0" (0));
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# else
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__asm__("bsrl %1,%0"
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: "=r" (n)
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: "rm" (defang_zero(v)));
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# endif
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return n;
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}
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# elif defined(HAVE__BITSCANREVERSE)
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extern_inline unsigned int const_func ilog2_32(uint32_t v)
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{
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unsigned long ix;
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return _BitScanReverse(&ix, v) ? v : 0;
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}
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# else
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extern_inline unsigned int const_func ilog2_32(uint32_t v)
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{
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unsigned int p = 0;
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ROUND(v, p, 16);
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ROUND(v, p, 8);
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ROUND(v, p, 4);
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ROUND(v, p, 2);
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ROUND(v, p, 1);
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return p;
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}
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# endif
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# if defined(HAVE__BUILTIN_CLZLL) && LLONG_MAX == 9223372036854775807LL
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extern_inline unsigned int const_func ilog2_64(uint64_t v)
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{
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return __builtin_clzll(defang_zero(v)) ^ 63;
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}
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# elif defined(__GNUC__) && defined(__x86_64__)
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extern_inline unsigned int const_func ilog2_64(uint64_t v)
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{
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uint64_t n;
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__asm__("bsrq %1,%0"
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: "=r" (n)
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: "rm" (v), "0" (UINT64_C(0)));
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return n;
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}
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# elif defined(HAVE__BITSCANREVERSE64)
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extern_inline unsigned int const_func ilog2_64(uint64_t v)
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{
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unsigned long ix;
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return _BitScanReverse64(&ix, v) ? ix : 0;
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}
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# else
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extern_inline unsigned int const_func ilog2_64(uint64_t vv)
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{
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unsigned int p = 0;
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uint32_t v;
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v = vv >> 32;
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if (v)
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p += 32;
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else
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v = vv;
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return p + ilog2_32(v);
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}
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# endif
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# endif
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/*
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* v == 0 ? 0 : is_power2(x) ? ilog2_X(v) : -1
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*/
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extern_inline int const_func alignlog2_32(uint32_t v)
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{
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if (unlikely(v & (v-1)))
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return -1; /* invalid alignment */
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return ilog2_32(v);
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}
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extern_inline int const_func alignlog2_64(uint64_t v)
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{
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if (unlikely(v & (v-1)))
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return -1; /* invalid alignment */
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return ilog2_64(v);
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}
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#undef ROUND
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#endif /* extern_inline */
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#endif /* ILOG2_H */
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