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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-exception4 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 11long 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 cases23 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