1 /* This file is distributed under the University of Illinois Open Source
2 * License. See LICENSE.TXT for details.
5 /* long double __gcc_qadd(long double x, long double y);
6 * This file implements the PowerPC 128-bit double-double add operation.
7 * This implementation is shamelessly cribbed from Apple's DDRT, circa 1993(!)
12 long double __gcc_qadd(long double x, long double y)
14 static const uint32_t infinityHi = UINT32_C(0x7ff00000);
16 DD dst = { .ld = x }, src = { .ld = y };
18 register double A = dst.s.hi, a = dst.s.lo,
19 B = src.s.hi, b = src.s.lo;
21 /* If both operands are zero: */
22 if ((A == 0.0) && (B == 0.0)) {
28 /* If either operand is NaN or infinity: */
29 const doublebits abits = { .d = A };
30 const doublebits bbits = { .d = B };
31 if ((((uint32_t)(abits.x >> 32) & infinityHi) == infinityHi) ||
32 (((uint32_t)(bbits.x >> 32) & infinityHi) == infinityHi)) {
38 /* If the computation overflows: */
39 /* This may be playing things a little bit fast and loose, but it will do for a start. */
40 const double testForOverflow = A + (B + (a + b));
41 const doublebits testbits = { .d = testForOverflow };
42 if (((uint32_t)(testbits.x >> 32) & infinityHi) == infinityHi) {
43 dst.s.hi = testForOverflow;
53 H = B + (A - (A + B));
54 T = b + (a - (a + b));
55 h = A + (B - (A + B));
56 t = a + (b - (a + b));
58 if (fabs(A) <= fabs(B))
67 if (fabs(a) <= fabs(b))
73 dst.s.lo = (W - Y) + w;