forked from OSchip/llvm-project
41 lines
1.2 KiB
C
41 lines
1.2 KiB
C
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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// long double __floatunditf(unsigned long long x);
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// This file implements the PowerPC unsigned long long -> long double conversion
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#include "DD.h"
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#include <stdint.h>
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long double __floatunditf(uint64_t a) {
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// Begins with an exact copy of the code from __floatundidf
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static const double twop52 = 0x1.0p52;
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static const double twop84 = 0x1.0p84;
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static const double twop84_plus_twop52 = 0x1.00000001p84;
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doublebits high = { .d = twop84 };
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doublebits low = { .d = twop52 };
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high.x |= a >> 32; // 0x1.0p84 + high 32 bits of a
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low.x |= a & UINT64_C(0x00000000ffffffff); // 0x1.0p52 + low 32 bits of a
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const double high_addend = high.d - twop84_plus_twop52;
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// At this point, we have two double precision numbers
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// high_addend and low.d, and we wish to return their sum
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// as a canonicalized long double:
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// This implementation sets the inexact flag spuriously.
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// This could be avoided, but at some substantial cost.
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DD result;
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result.hi = high_addend + low.d;
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result.lo = (high_addend - result.hi) + low.d;
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return result.ld;
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}
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