27 lines
460 B
C
27 lines
460 B
C
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#include "libc/limits.h"
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#include "libc/math/libm.h"
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int ilogb(double x)
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{
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#pragma STDC FENV_ACCESS ON
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union {double f; uint64_t i;} u = {x};
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uint64_t i = u.i;
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int e = i>>52 & 0x7ff;
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if (!e) {
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i <<= 12;
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if (i == 0) {
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FORCE_EVAL(0/0.0f);
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return FP_ILOGB0;
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}
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/* subnormal x */
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for (e = -0x3ff; i>>63 == 0; e--, i<<=1);
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return e;
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}
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if (e == 0x7ff) {
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FORCE_EVAL(0/0.0f);
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return i<<12 ? FP_ILOGBNAN : INT_MAX;
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}
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return e - 0x3ff;
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}
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