| 1 | /* s_ilogbl.c -- long double version of s_ilogb.c. |
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| 2 | */ |
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| 3 | |
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| 4 | /* |
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| 5 | * ==================================================== |
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| 6 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 7 | * |
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| 8 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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| 9 | * Permission to use, copy, modify, and distribute this |
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| 10 | * software is freely granted, provided that this notice |
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| 11 | * is preserved. |
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| 12 | * ==================================================== |
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| 13 | */ |
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| 14 | |
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| 15 | #if defined(LIBM_SCCS) && !defined(lint) |
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| 16 | static char rcsid[] = "$NetBSD: $" ; |
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| 17 | #endif |
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| 18 | |
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| 19 | /* ilogbl(long double x) |
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| 20 | * return the binary exponent of non-zero x |
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| 21 | * ilogbl(0) = FP_ILOGB0 |
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| 22 | * ilogbl(NaN) = FP_ILOGBNAN (no signal is raised) |
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| 23 | * ilogbl(+-Inf) = INT_MAX (no signal is raised) |
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| 24 | */ |
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| 25 | |
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| 26 | #include <limits.h> |
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| 27 | #include <math.h> |
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| 28 | #include <math_private.h> |
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| 29 | #include <math_ldbl_opt.h> |
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| 30 | |
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| 31 | int __ieee754_ilogbl(long double x) |
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| 32 | { |
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| 33 | int64_t hx, hxs; |
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| 34 | int ix; |
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| 35 | double xhi, xlo; |
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| 36 | |
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| 37 | ldbl_unpack (x, &xhi, &xlo); |
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| 38 | EXTRACT_WORDS64 (hx, xhi); |
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| 39 | hxs = hx; |
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| 40 | hx &= 0x7fffffffffffffffLL; |
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| 41 | if(hx <= 0x0010000000000000LL) { |
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| 42 | if(hx==0) |
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| 43 | return FP_ILOGB0; /* ilogbl(0) = FP_ILOGB0 */ |
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| 44 | else /* subnormal x */ |
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| 45 | for (ix = -1022, hx<<=11; hx>0; hx<<=1) ix -=1; |
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| 46 | return ix; |
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| 47 | } |
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| 48 | else if (hx < 0x7ff0000000000000LL) |
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| 49 | { |
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| 50 | int hexp = (hx >> 52) - 0x3ff; |
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| 51 | /* If the high part is a power of 2, and the low part is |
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| 52 | nonzero with the opposite sign, the low part affects |
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| 53 | the exponent. */ |
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| 54 | if ((hx & 0x000fffffffffffffLL) == 0) |
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| 55 | { |
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| 56 | int64_t lx; |
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| 57 | EXTRACT_WORDS64 (lx, xlo); |
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| 58 | if ((hxs ^ lx) < 0 && (lx & 0x7fffffffffffffffLL) != 0) |
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| 59 | hexp--; |
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| 60 | } |
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| 61 | return hexp; |
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| 62 | } |
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| 63 | else if (FP_ILOGBNAN != INT_MAX) { |
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| 64 | /* ISO C99 requires ilogbl(+-Inf) == INT_MAX. */ |
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| 65 | if (hx==0x7ff0000000000000LL) |
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| 66 | return INT_MAX; |
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| 67 | } |
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| 68 | return FP_ILOGBNAN; |
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| 69 | } |
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| 70 | |
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