| 1 | static double convert_to_double_core(const uint64_t* limb, int sz, int exp, bool sign) {
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| 2 | uint64_t lsbits = 0;
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| 3 | for (int i = 0; i < sz - 1; ++i)
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| 4 | lsbits |= limb[i];
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| 5 | uint64_t msw = limb[sz-1];
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| 6 | lsbits |= msw & 1;
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| 7 |
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| 8 | // Don't use uint64_t -> double conversion, because there are compilers,
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| 9 | // in particular MS VisualC++, that for some versions on some platform (I saw it on VS2013/x64/avx)
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| 10 | // does not implement this conversion well when the argument is >= 2^63, i.e. exactly in our case.
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| 11 | // On the other hand int64_t -> double conversion appears to be robust on all platforms that I tested
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| 12 |
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| 13 | int64_t m = msw >> 1;
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| 14 | if (lsbits) m |= 1;
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| 15 | if (sign) m = -m;
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| 16 | return ldexp(m, exp-62);
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| 17 | }
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