142 lines
4.2 KiB
C
142 lines
4.2 KiB
C
#ifndef BIGDECIMAL_BITS_H
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#define BIGDECIMAL_BITS_H
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#include "feature.h"
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#include "static_assert.h"
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#if defined(__x86_64__) && defined(HAVE_X86INTRIN_H)
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# include <x86intrin.h> /* for _lzcnt_u64, etc. */
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#elif defined(_MSC_VER) && defined(HAVE_INTRIN_H)
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# include <intrin.h> /* for the following intrinsics */
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#endif
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#if defined(_MSC_VER) && defined(__AVX2__)
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# pragma intrinsic(__lzcnt)
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# pragma intrinsic(__lzcnt64)
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#endif
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#define numberof(array) ((int)(sizeof(array) / sizeof((array)[0])))
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#define roomof(x, y) (((x) + (y) - 1) / (y))
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#define type_roomof(x, y) roomof(sizeof(x), sizeof(y))
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#define MUL_OVERFLOW_SIGNED_INTEGER_P(a, b, min, max) ( \
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(a) == 0 ? 0 : \
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(a) == -1 ? (b) < -(max) : \
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(a) > 0 ? \
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((b) > 0 ? (max) / (a) < (b) : (min) / (a) > (b)) : \
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((b) > 0 ? (min) / (a) < (b) : (max) / (a) > (b)))
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#ifdef HAVE_UINT128_T
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# define bit_length(x) \
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(unsigned int) \
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(sizeof(x) <= sizeof(int32_t) ? 32 - nlz_int32((uint32_t)(x)) : \
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sizeof(x) <= sizeof(int64_t) ? 64 - nlz_int64((uint64_t)(x)) : \
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128 - nlz_int128((uint128_t)(x)))
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#else
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# define bit_length(x) \
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(unsigned int) \
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(sizeof(x) <= sizeof(int32_t) ? 32 - nlz_int32((uint32_t)(x)) : \
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64 - nlz_int64((uint64_t)(x)))
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#endif
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static inline unsigned nlz_int32(uint32_t x);
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static inline unsigned nlz_int64(uint64_t x);
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#ifdef HAVE_UINT128_T
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static inline unsigned nlz_int128(uint128_t x);
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#endif
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static inline unsigned int
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nlz_int32(uint32_t x)
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{
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#if defined(_MSC_VER) && defined(__AVX2__) && defined(HAVE___LZCNT)
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/* Note: It seems there is no such thing like __LZCNT__ predefined in MSVC.
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* AMD CPUs have had this instruction for decades (since K10) but for
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* Intel, Haswell is the oldest one. We need to use __AVX2__ for maximum
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* safety. */
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return (unsigned int)__lzcnt(x);
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#elif defined(__x86_64__) && defined(__LZCNT__) && defined(HAVE__LZCNT_U32)
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return (unsigned int)_lzcnt_u32(x);
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#elif defined(_MSC_VER) && defined(HAVE__BITSCANREVERSE)
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unsigned long r;
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return _BitScanReverse(&r, x) ? (31 - (int)r) : 32;
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#elif __has_builtin(__builtin_clz)
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STATIC_ASSERT(sizeof_int, sizeof(int) * CHAR_BIT == 32);
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return x ? (unsigned int)__builtin_clz(x) : 32;
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#else
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uint32_t y;
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unsigned n = 32;
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y = x >> 16; if (y) {n -= 16; x = y;}
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y = x >> 8; if (y) {n -= 8; x = y;}
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y = x >> 4; if (y) {n -= 4; x = y;}
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y = x >> 2; if (y) {n -= 2; x = y;}
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y = x >> 1; if (y) {return n - 2;}
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return (unsigned int)(n - x);
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#endif
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}
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static inline unsigned int
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nlz_int64(uint64_t x)
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{
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#if defined(_MSC_VER) && defined(__AVX2__) && defined(HAVE___LZCNT64)
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return (unsigned int)__lzcnt64(x);
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#elif defined(__x86_64__) && defined(__LZCNT__) && defined(HAVE__LZCNT_U64)
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return (unsigned int)_lzcnt_u64(x);
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#elif defined(_WIN64) && defined(_MSC_VER) && defined(HAVE__BITSCANREVERSE64)
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unsigned long r;
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return _BitScanReverse64(&r, x) ? (63u - (unsigned int)r) : 64;
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#elif __has_builtin(__builtin_clzl) && __has_builtin(__builtin_clzll) && !(defined(__sun) && defined(__sparc))
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if (x == 0) {
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return 64;
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}
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else if (sizeof(long) * CHAR_BIT == 64) {
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return (unsigned int)__builtin_clzl((unsigned long)x);
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}
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else if (sizeof(long long) * CHAR_BIT == 64) {
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return (unsigned int)__builtin_clzll((unsigned long long)x);
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}
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else {
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/* :FIXME: Is there a way to make this branch a compile-time error? */
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__builtin_unreachable();
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}
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#else
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uint64_t y;
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unsigned int n = 64;
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y = x >> 32; if (y) {n -= 32; x = y;}
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y = x >> 16; if (y) {n -= 16; x = y;}
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y = x >> 8; if (y) {n -= 8; x = y;}
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y = x >> 4; if (y) {n -= 4; x = y;}
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y = x >> 2; if (y) {n -= 2; x = y;}
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y = x >> 1; if (y) {return n - 2;}
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return (unsigned int)(n - x);
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#endif
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}
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#ifdef HAVE_UINT128_T
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static inline unsigned int
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nlz_int128(uint128_t x)
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{
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uint64_t y = (uint64_t)(x >> 64);
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if (x == 0) {
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return 128;
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}
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else if (y == 0) {
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return (unsigned int)nlz_int64(x) + 64;
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}
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else {
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return (unsigned int)nlz_int64(y);
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}
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}
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#endif
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#endif /* BIGDECIMAL_BITS_H */
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