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Fix another roundToIntegral bug where very large values could become infinity. Problem and solution identified by Steve Canon.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161969 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2012-08-15 18:28:45 +00:00
parent c97eda2c9e
commit c82cc587a4
2 changed files with 20 additions and 1 deletions
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6
lib/Support/APFloat.cpp
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@ -1770,6 +1770,12 @@ 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

15
unittests/ADT/APFloatTest.cpp
View File

@ -649,7 +649,7 @@ TEST(APFloatTest, exactInverse) {
}
TEST(APFloatTest, roundToIntegral) {
APFloat T(-0.5), S(3.14), P(0.0);
APFloat T(-0.5), S(3.14), R(APFloat::getLargest(APFloat::IEEEdouble)), P(0.0);
P = T;
P.roundToIntegral(APFloat::rmTowardZero);
@ -676,6 +676,19 @@ TEST(APFloatTest, roundToIntegral) {
P = S;
P.roundToIntegral(APFloat::rmNearestTiesToEven);
EXPECT_EQ(3.0, P.convertToDouble());
P = R;
P.roundToIntegral(APFloat::rmTowardZero);
EXPECT_EQ(R.convertToDouble(), P.convertToDouble());
P = R;
P.roundToIntegral(APFloat::rmTowardNegative);
EXPECT_EQ(R.convertToDouble(), P.convertToDouble());
P = R;
P.roundToIntegral(APFloat::rmTowardPositive);
EXPECT_EQ(R.convertToDouble(), P.convertToDouble());
P = R;
P.roundToIntegral(APFloat::rmNearestTiesToEven);
EXPECT_EQ(R.convertToDouble(), P.convertToDouble());
}
TEST(APFloatTest, getLargest) {