diff options
Diffstat (limited to 'lib/Support/APFloat.cpp')
| -rw-r--r-- | lib/Support/APFloat.cpp | 22 |
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; } |
