forked from OSchip/llvm-project
52 lines
1.2 KiB
C
52 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 __gcc_qmul(long double x, long double y);
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// This file implements the PowerPC 128-bit double-double multiply operation.
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// This implementation is shamelessly cribbed from Apple's DDRT, circa 1993(!)
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#include "DD.h"
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long double __gcc_qmul(long double x, long double y)
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{
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static const uint32_t infinityHi = UINT32_C(0x7ff00000);
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DD dst = { .ld = x }, src = { .ld = y };
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register double A = dst.hi, a = dst.lo,
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B = src.hi, b = src.lo;
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double aHi, aLo, bHi, bLo;
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double ab, tmp, tau;
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ab = A * B;
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// Detect special cases
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if (ab == 0.0) {
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dst.hi = ab;
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dst.lo = 0.0;
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return dst.ld;
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}
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const doublebits abBits = { .d = ab };
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if (((uint32_t)(abBits.x >> 32) & infinityHi) == infinityHi) {
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dst.hi = ab;
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dst.lo = 0.0;
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return dst.ld;
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}
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// Generic cases handled here.
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aHi = high26bits(A);
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bHi = high26bits(B);
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aLo = A - aHi;
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bLo = B - bHi;
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tmp = LOWORDER(ab, aHi, aLo, bHi, bLo);
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tmp += (A * b + a * B);
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tau = ab + tmp;
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dst.lo = (ab - tau) + tmp;
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dst.hi = tau;
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return dst.ld;
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}
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