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51 lines
1.2 KiB
51 lines
1.2 KiB
7 months ago
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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// long double __gcc_qmul(long double x, long double y);
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// This file implements the PowerPC 128-bit double-double multiply operation.
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// This implementation is shamelessly cribbed from Apple's DDRT, circa 1993(!)
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#include "DD.h"
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long double __gcc_qmul(long double x, long double y) {
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static const uint32_t infinityHi = UINT32_C(0x7ff00000);
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DD dst = {.ld = x}, src = {.ld = y};
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register double A = dst.s.hi, a = dst.s.lo, B = src.s.hi, b = src.s.lo;
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double aHi, aLo, bHi, bLo;
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double ab, tmp, tau;
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ab = A * B;
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// Detect special cases
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if (ab == 0.0) {
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dst.s.hi = ab;
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dst.s.lo = 0.0;
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return dst.ld;
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}
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const doublebits abBits = {.d = ab};
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if (((uint32_t)(abBits.x >> 32) & infinityHi) == infinityHi) {
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dst.s.hi = ab;
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dst.s.lo = 0.0;
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return dst.ld;
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}
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// Generic cases handled here.
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aHi = high26bits(A);
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bHi = high26bits(B);
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aLo = A - aHi;
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bLo = B - bHi;
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tmp = LOWORDER(ab, aHi, aLo, bHi, bLo);
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tmp += (A * b + a * B);
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tau = ab + tmp;
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dst.s.lo = (ab - tau) + tmp;
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dst.s.hi = tau;
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return dst.ld;
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}
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