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[ADT] Add the scalbn function for APFloat. 

llvm-svn: 219473
This commit is contained in:
Chandler Carruth 2014-10-10 04:54:30 +00:00
parent e16b92db2d
commit d9edd1e2ab
3 changed files with 66 additions and 2 deletions
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8
llvm/include/llvm/ADT/APFloat.h
View File

@ -507,6 +507,9 @@ public:
return Result; return Result;
} }
/// \brief Returns: X * 2^Exp for integral exponents.
friend APFloat scalbn(APFloat X, int Exp);
private: private:
/// \name Simple Queries /// \name Simple Queries
@ -628,11 +631,12 @@ private:
unsigned int sign : 1; unsigned int sign : 1;
}; };
/// See friend declaration above. /// See friend declarations above.
/// ///
/// This additional declaration is required in order to compile LLVM with IBM /// These additional declarations are required in order to compile LLVM with IBM
/// xlC compiler. /// xlC compiler.
hash_code hash_value(const APFloat &Arg); hash_code hash_value(const APFloat &Arg);
APFloat scalbn(APFloat X, int Exp);
} // namespace llvm } // namespace llvm

17
llvm/lib/Support/APFloat.cpp
View File

@ -3906,3 +3906,20 @@ APFloat::makeZero(bool Negative) {
exponent = semantics->minExponent-1; exponent = semantics->minExponent-1;
APInt::tcSet(significandParts(), 0, partCount()); APInt::tcSet(significandParts(), 0, partCount());
} }
APFloat llvm::scalbn(APFloat X, int Exp) {
if (X.isInfinity() || X.isZero() || X.isNaN())
return std::move(X);
auto MaxExp = X.getSemantics().maxExponent;
auto MinExp = X.getSemantics().minExponent;
if (Exp > (MaxExp - X.exponent))
// Overflow saturates to infinity.
return APFloat::getInf(X.getSemantics(), X.isNegative());
if (Exp < (MinExp - X.exponent))
// Underflow saturates to zero.
return APFloat::getZero(X.getSemantics(), X.isNegative());
X.exponent += Exp;
return std::move(X);
}

43
llvm/unittests/ADT/APFloatTest.cpp
View File

@ -2742,4 +2742,47 @@ TEST(APFloatTest, logb) {
EXPECT_TRUE(APFloat(APFloat::IEEEsingle, "-0x7Ep+0") EXPECT_TRUE(APFloat(APFloat::IEEEsingle, "-0x7Ep+0")
.bitwiseIsEqual(logb(MSmallestNormalized))); .bitwiseIsEqual(logb(MSmallestNormalized)));
} }
TEST(APFloatTest, scalbn) {
EXPECT_TRUE(
APFloat(APFloat::IEEEsingle, "0x1p+0")
.bitwiseIsEqual(scalbn(APFloat(APFloat::IEEEsingle, "0x1p+0"), 0)));
EXPECT_TRUE(
APFloat(APFloat::IEEEsingle, "0x1p+42")
.bitwiseIsEqual(scalbn(APFloat(APFloat::IEEEsingle, "0x1p+0"), 42)));
EXPECT_TRUE(
APFloat(APFloat::IEEEsingle, "0x1p-42")
.bitwiseIsEqual(scalbn(APFloat(APFloat::IEEEsingle, "0x1p+0"), -42)));
APFloat PInf = APFloat::getInf(APFloat::IEEEsingle, false);
APFloat MInf = APFloat::getInf(APFloat::IEEEsingle, true);
APFloat PZero = APFloat::getZero(APFloat::IEEEsingle, false);
APFloat MZero = APFloat::getZero(APFloat::IEEEsingle, true);
APFloat QPNaN = APFloat::getNaN(APFloat::IEEEsingle, false);
APFloat QMNaN = APFloat::getNaN(APFloat::IEEEsingle, true);
APFloat SNaN = APFloat::getSNaN(APFloat::IEEEsingle, false);
EXPECT_TRUE(PInf.bitwiseIsEqual(scalbn(PInf, 0)));
EXPECT_TRUE(MInf.bitwiseIsEqual(scalbn(MInf, 0)));
EXPECT_TRUE(PZero.bitwiseIsEqual(scalbn(PZero, 0)));
EXPECT_TRUE(MZero.bitwiseIsEqual(scalbn(MZero, 0)));
EXPECT_TRUE(QPNaN.bitwiseIsEqual(scalbn(QPNaN, 0)));
EXPECT_TRUE(QMNaN.bitwiseIsEqual(scalbn(QMNaN, 0)));
EXPECT_TRUE(SNaN.bitwiseIsEqual(scalbn(SNaN, 0)));
EXPECT_TRUE(
PInf.bitwiseIsEqual(scalbn(APFloat(APFloat::IEEEsingle, "0x1p+0"), 128)));
EXPECT_TRUE(MInf.bitwiseIsEqual(
scalbn(APFloat(APFloat::IEEEsingle, "-0x1p+0"), 128)));
EXPECT_TRUE(
PInf.bitwiseIsEqual(scalbn(APFloat(APFloat::IEEEsingle, "0x1p+127"), 1)));
EXPECT_TRUE(PZero.bitwiseIsEqual(
scalbn(APFloat(APFloat::IEEEsingle, "0x1p+0"), -127)));
EXPECT_TRUE(MZero.bitwiseIsEqual(
scalbn(APFloat(APFloat::IEEEsingle, "-0x1p+0"), -127)));
EXPECT_TRUE(PZero.bitwiseIsEqual(
scalbn(APFloat(APFloat::IEEEsingle, "0x1p-126"), -1)));
EXPECT_TRUE(PZero.bitwiseIsEqual(
scalbn(APFloat(APFloat::IEEEsingle, "0x1p-126"), -1)));
}
} }