1*3cab2bb3Spatrick // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
2*3cab2bb3Spatrick // See https://llvm.org/LICENSE.txt for license information.
3*3cab2bb3Spatrick // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
4*3cab2bb3Spatrick
5*3cab2bb3Spatrick // long double __gcc_qmul(long double x, long double y);
6*3cab2bb3Spatrick // This file implements the PowerPC 128-bit double-double multiply operation.
7*3cab2bb3Spatrick // This implementation is shamelessly cribbed from Apple's DDRT, circa 1993(!)
8*3cab2bb3Spatrick
9*3cab2bb3Spatrick #include "DD.h"
10*3cab2bb3Spatrick
__gcc_qmul(long double x,long double y)11*3cab2bb3Spatrick long double __gcc_qmul(long double x, long double y) {
12*3cab2bb3Spatrick static const uint32_t infinityHi = UINT32_C(0x7ff00000);
13*3cab2bb3Spatrick DD dst = {.ld = x}, src = {.ld = y};
14*3cab2bb3Spatrick
15*3cab2bb3Spatrick register double A = dst.s.hi, a = dst.s.lo, B = src.s.hi, b = src.s.lo;
16*3cab2bb3Spatrick
17*3cab2bb3Spatrick double aHi, aLo, bHi, bLo;
18*3cab2bb3Spatrick double ab, tmp, tau;
19*3cab2bb3Spatrick
20*3cab2bb3Spatrick ab = A * B;
21*3cab2bb3Spatrick
22*3cab2bb3Spatrick // Detect special cases
23*3cab2bb3Spatrick if (ab == 0.0) {
24*3cab2bb3Spatrick dst.s.hi = ab;
25*3cab2bb3Spatrick dst.s.lo = 0.0;
26*3cab2bb3Spatrick return dst.ld;
27*3cab2bb3Spatrick }
28*3cab2bb3Spatrick
29*3cab2bb3Spatrick const doublebits abBits = {.d = ab};
30*3cab2bb3Spatrick if (((uint32_t)(abBits.x >> 32) & infinityHi) == infinityHi) {
31*3cab2bb3Spatrick dst.s.hi = ab;
32*3cab2bb3Spatrick dst.s.lo = 0.0;
33*3cab2bb3Spatrick return dst.ld;
34*3cab2bb3Spatrick }
35*3cab2bb3Spatrick
36*3cab2bb3Spatrick // Generic cases handled here.
37*3cab2bb3Spatrick aHi = high26bits(A);
38*3cab2bb3Spatrick bHi = high26bits(B);
39*3cab2bb3Spatrick aLo = A - aHi;
40*3cab2bb3Spatrick bLo = B - bHi;
41*3cab2bb3Spatrick
42*3cab2bb3Spatrick tmp = LOWORDER(ab, aHi, aLo, bHi, bLo);
43*3cab2bb3Spatrick tmp += (A * b + a * B);
44*3cab2bb3Spatrick tau = ab + tmp;
45*3cab2bb3Spatrick
46*3cab2bb3Spatrick dst.s.lo = (ab - tau) + tmp;
47*3cab2bb3Spatrick dst.s.hi = tau;
48*3cab2bb3Spatrick
49*3cab2bb3Spatrick return dst.ld;
50*3cab2bb3Spatrick }
51