Vendor import of llvm trunk r162107:

http://llvm.org/svn/llvm-project/llvm/trunk@162107

1 files changed, 20 insertions, 2 deletions

diff --git a/lib/Support/APFloat.cpp b/lib/Support/APFloat.cpp
index 2139df5..ed261a4 100644
--- a/lib/Support/APFloat.cpp
+++ b/lib/Support/APFloat.cpp
@@ -1770,23 +1770,41 @@ APFloat::opStatus APFloat::roundToIntegral(roundingMode rounding_mode) {
   opStatus fs;
   assertArithmeticOK(*semantics);
 
+  // If the exponent is large enough, we know that this value is already
+  // integral, and the arithmetic below would potentially cause it to saturate
+  // to +/-Inf.  Bail out early instead.
+  if (exponent+1 >= (int)semanticsPrecision(*semantics))
+    return opOK;
+
   // The algorithm here is quite simple: we add 2^(p-1), where p is the
   // precision of our format, and then subtract it back off again.  The choice
   // of rounding modes for the addition/subtraction determines the rounding mode
   // for our integral rounding as well.
-  APInt IntegerConstant(NextPowerOf2(semanticsPrecision(*semantics)),
-                        1 << (semanticsPrecision(*semantics)-1));
+  // NOTE: When the input value is negative, we do subtraction followed by
+  // addition instead.
+  APInt IntegerConstant(NextPowerOf2(semanticsPrecision(*semantics)), 1);
+  IntegerConstant <<= semanticsPrecision(*semantics)-1;
   APFloat MagicConstant(*semantics);
   fs = MagicConstant.convertFromAPInt(IntegerConstant, false,
                                       rmNearestTiesToEven);
+  MagicConstant.copySign(*this);
+
   if (fs != opOK)
     return fs;
 
+  // Preserve the input sign so that we can handle 0.0/-0.0 cases correctly.
+  bool inputSign = isNegative();
+
   fs = add(MagicConstant, rounding_mode);
   if (fs != opOK && fs != opInexact)
     return fs;
 
   fs = subtract(MagicConstant, rounding_mode);
+
+  // Restore the input sign.
+  if (inputSign != isNegative())
+    changeSign();
+
   return fs;
 }