1 files changed, 44 insertions, 13 deletions

diff --git a/lib/Support/APFloat.cpp b/lib/Support/APFloat.cpp
index e765ba0..c3169ac 100644
--- a/lib/Support/APFloat.cpp
+++ b/lib/Support/APFloat.cpp
@@ -726,7 +726,7 @@ APFloat::bitwiseIsEqual(const APFloat &rhs) const {
 }
 
 APFloat::APFloat(const fltSemantics &ourSemantics, integerPart value)
-{
+  : exponent2(0), sign2(0) {
   assertArithmeticOK(ourSemantics);
   initialize(&ourSemantics);
   sign = 0;
@@ -736,14 +736,15 @@ APFloat::APFloat(const fltSemantics &ourSemantics, integerPart value)
   normalize(rmNearestTiesToEven, lfExactlyZero);
 }
 
-APFloat::APFloat(const fltSemantics &ourSemantics) {
+APFloat::APFloat(const fltSemantics &ourSemantics) : exponent2(0), sign2(0) {
   assertArithmeticOK(ourSemantics);
   initialize(&ourSemantics);
   category = fcZero;
   sign = false;
 }
 
-APFloat::APFloat(const fltSemantics &ourSemantics, uninitializedTag tag) {
+APFloat::APFloat(const fltSemantics &ourSemantics, uninitializedTag tag)
+  : exponent2(0), sign2(0) {
   assertArithmeticOK(ourSemantics);
   // Allocates storage if necessary but does not initialize it.
   initialize(&ourSemantics);
@@ -751,7 +752,7 @@ APFloat::APFloat(const fltSemantics &ourSemantics, uninitializedTag tag) {
 
 APFloat::APFloat(const fltSemantics &ourSemantics,
                  fltCategory ourCategory, bool negative)
-{
+  : exponent2(0), sign2(0) {
   assertArithmeticOK(ourSemantics);
   initialize(&ourSemantics);
   category = ourCategory;
@@ -763,14 +764,13 @@ APFloat::APFloat(const fltSemantics &ourSemantics,
 }
 
 APFloat::APFloat(const fltSemantics &ourSemantics, StringRef text)
-{
+  : exponent2(0), sign2(0) {
   assertArithmeticOK(ourSemantics);
   initialize(&ourSemantics);
   convertFromString(text, rmNearestTiesToEven);
 }
 
-APFloat::APFloat(const APFloat &rhs)
-{
+APFloat::APFloat(const APFloat &rhs) : exponent2(0), sign2(0) {
   initialize(rhs.semantics);
   assign(rhs);
 }
@@ -3257,18 +3257,15 @@ APFloat APFloat::getSmallestNormalized(const fltSemantics &Sem, bool Negative) {
   return Val;
 }
 
-APFloat::APFloat(const APInt& api, bool isIEEE)
-{
+APFloat::APFloat(const APInt& api, bool isIEEE) : exponent2(0), sign2(0) {
   initFromAPInt(api, isIEEE);
 }
 
-APFloat::APFloat(float f)
-{
+APFloat::APFloat(float f) : exponent2(0), sign2(0) {
   initFromAPInt(APInt::floatToBits(f));
 }
 
-APFloat::APFloat(double d)
-{
+APFloat::APFloat(double d) : exponent2(0), sign2(0) {
   initFromAPInt(APInt::doubleToBits(d));
 }
 
@@ -3565,3 +3562,37 @@ void APFloat::toString(SmallVectorImpl<char> &Str,
   for (; I != NDigits; ++I)
     Str.push_back(buffer[NDigits-I-1]);
 }
+
+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;
+}