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35 lines
994 B
C
35 lines
994 B
C
#ifndef COSMOPOLITAN_LIBC_TINYMATH_MAGICU_H_
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#define COSMOPOLITAN_LIBC_TINYMATH_MAGICU_H_
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#if !(__ASSEMBLER__ + __LINKER__ + 0)
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COSMOPOLITAN_C_START_
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struct magicu {
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uint32_t M;
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uint32_t s;
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};
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struct magicu __magicu_get(uint32_t);
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/**
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* Performs fast division using precomputed magic for constant divisor.
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*
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* @param x is unsigned integer that shall be divided
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* @param d should be `__magicu_get(y)` if computing `x / y`
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* @return result of unsigned integer division
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*/
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forceinline uint32_t __magicu_div(uint32_t x, struct magicu d) {
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return ((((uint64_t)x * d.M) >> 32) + ((d.s & 64) ? x : 0)) >> (d.s & 63);
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}
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/**
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* Checks if 𝑑 contains a valid initialized divisor.
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*/
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static inline bool32 __magicu_valid(struct magicu d) {
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if (!d.M && !d.s) return false; /* uninitialized */
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if (d.s & ~(64 | 63)) return false; /* corrupted */
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return true;
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}
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COSMOPOLITAN_C_END_
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#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
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#endif /* COSMOPOLITAN_LIBC_TINYMATH_MAGICU_H_ */
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