+
+bool APFloat::getExactInverse(APFloat *inv) const {
+ // We can only guarantee the existence of an exact inverse for IEEE floats.
+ if (semantics != &IEEEhalf && semantics != &IEEEsingle &&
+ semantics != &IEEEdouble && semantics != &IEEEquad)
+ return false;
+
+ // Special floats and denormals have no exact inverse.
+ if (category != fcNormal)
+ return false;
+
+ // Check that the number is a power of two by making sure that only the
+ // integer bit is set in the significand.
+ if (significandLSB() != semantics->precision - 1)
+ return false;
+
+ // Get the inverse.
+ APFloat reciprocal(*semantics, 1ULL);
+ if (reciprocal.divide(*this, rmNearestTiesToEven) != opOK)
+ return false;
+
+ // Avoid multiplication with a denormal, it is not safe on all platforms and
+ // may be slower than a normal division.
+ if (reciprocal.significandMSB() + 1 < reciprocal.semantics->precision)
+ return false;
+
+ assert(reciprocal.category == fcNormal &&
+ reciprocal.significandLSB() == reciprocal.semantics->precision - 1);
+
+ if (inv)
+ *inv = reciprocal;
+
+ return true;
+}