- uint64_t myexponent, mysignificand, myexponent2, mysignificand2;
-
- if (category==fcNormal) {
- myexponent = exponent + 1023; //bias
- myexponent2 = exponent2 + 1023;
- mysignificand = significandParts()[0];
- mysignificand2 = significandParts()[1];
- if (myexponent==1 && !(mysignificand & 0x10000000000000LL))
- myexponent = 0; // denormal
- if (myexponent2==1 && !(mysignificand2 & 0x10000000000000LL))
- myexponent2 = 0; // denormal
- } else if (category==fcZero) {
- myexponent = 0;
- mysignificand = 0;
- myexponent2 = 0;
- mysignificand2 = 0;
- } else if (category==fcInfinity) {
- myexponent = 0x7ff;
- myexponent2 = 0;
- mysignificand = 0;
- mysignificand2 = 0;
+ uint64_t words[2];
+ opStatus fs;
+ bool losesInfo;
+
+ // Convert number to double. To avoid spurious underflows, we re-
+ // normalize against the "double" minExponent first, and only *then*
+ // truncate the mantissa. The result of that second conversion
+ // may be inexact, but should never underflow.
+ // Declare fltSemantics before APFloat that uses it (and
+ // saves pointer to it) to ensure correct destruction order.
+ fltSemantics extendedSemantics = *semantics;
+ extendedSemantics.minExponent = IEEEdouble.minExponent;
+ APFloat extended(*this);
+ fs = extended.convert(extendedSemantics, rmNearestTiesToEven, &losesInfo);
+ assert(fs == opOK && !losesInfo);
+ (void)fs;
+
+ APFloat u(extended);
+ fs = u.convert(IEEEdouble, rmNearestTiesToEven, &losesInfo);
+ assert(fs == opOK || fs == opInexact);
+ (void)fs;
+ words[0] = *u.convertDoubleAPFloatToAPInt().getRawData();
+
+ // If conversion was exact or resulted in a special case, we're done;
+ // just set the second double to zero. Otherwise, re-convert back to
+ // the extended format and compute the difference. This now should
+ // convert exactly to double.
+ if (u.category == fcNormal && losesInfo) {
+ fs = u.convert(extendedSemantics, rmNearestTiesToEven, &losesInfo);
+ assert(fs == opOK && !losesInfo);
+ (void)fs;
+
+ APFloat v(extended);
+ v.subtract(u, rmNearestTiesToEven);
+ fs = v.convert(IEEEdouble, rmNearestTiesToEven, &losesInfo);
+ assert(fs == opOK && !losesInfo);
+ (void)fs;
+ words[1] = *v.convertDoubleAPFloatToAPInt().getRawData();