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/* This file is distributed under the University of Illinois Open Source
* License. See LICENSE.TXT for details.
*/
/* long double __gcc_qmul(long double x, long double y);
* This file implements the PowerPC 128-bit double-double multiply operation.
* This implementation is shamelessly cribbed from Apple's DDRT, circa 1993(!)
*/
#include "DD.h"
long double __gcc_qmul(long double x, long double y)
{
static const uint32_t infinityHi = UINT32_C(0x7ff00000);
DD dst = { .ld = x }, src = { .ld = y };
register double A = dst.s.hi, a = dst.s.lo,
B = src.s.hi, b = src.s.lo;
double aHi, aLo, bHi, bLo;
double ab, tmp, tau;
ab = A * B;
/* Detect special cases */
if (ab == 0.0) {
dst.s.hi = ab;
dst.s.lo = 0.0;
return dst.ld;
}
const doublebits abBits = { .d = ab };
if (((uint32_t)(abBits.x >> 32) & infinityHi) == infinityHi) {
dst.s.hi = ab;
dst.s.lo = 0.0;
return dst.ld;
}
/* Generic cases handled here. */
aHi = high26bits(A);
bHi = high26bits(B);
aLo = A - aHi;
bLo = B - bHi;
tmp = LOWORDER(ab, aHi, aLo, bHi, bLo);
tmp += (A * b + a * B);
tau = ab + tmp;
dst.s.lo = (ab - tau) + tmp;
dst.s.hi = tau;
return dst.ld;
}
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