llvm-project/compiler-rt/lib/ppc/gcc_qdiv.c

/* This file is distributed under the University of Illinois Open Source
 * License. See LICENSE.TXT for details.
 */

/* long double __gcc_qdiv(long double x, long double y);
 * This file implements the PowerPC 128-bit double-double division operation.
 * This implementation is shamelessly cribbed from Apple's DDRT, circa 1993(!)
 */

#include "DD.h"

long double __gcc_qdiv(long double a, long double b)
{	
	static const uint32_t infinityHi = UINT32_C(0x7ff00000);
	DD dst = { .ld = a }, src = { .ld = b };
	
	register double x = dst.s.hi, x1 = dst.s.lo,
					y = src.s.hi, y1 = src.s.lo;
	
    double yHi, yLo, qHi, qLo;
    double yq, tmp, q;
	
    q = x / y;
	
	/* Detect special cases */
	if (q == 0.0) {
		dst.s.hi = q;
		dst.s.lo = 0.0;
		return dst.ld;
	}
	
	const doublebits qBits = { .d = q };
	if (((uint32_t)(qBits.x >> 32) & infinityHi) == infinityHi) {
		dst.s.hi = q;
		dst.s.lo = 0.0;
		return dst.ld;
	}
	
    yHi = high26bits(y);
    qHi = high26bits(q);
	
    yq = y * q;
    yLo = y - yHi;
    qLo = q - qHi;
	
    tmp = LOWORDER(yq, yHi, yLo, qHi, qLo);
    tmp = (x - yq) - tmp;
    tmp = ((tmp + x1) - y1 * q) / y;
    x = q + tmp;
	
    dst.s.lo = (q - x) + tmp;
    dst.s.hi = x;
	
    return dst.ld;
}