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