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[ADT] Implement the 'logb' functionality for APFloat. This is necessary

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to implement complex division in the constant folder of Clang.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219471 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chandler Carruth 2014-10-10 04:17:04 +00:00
parent 9a97f23f2f
commit 9ea4dd2eed
2 changed files with 68 additions and 0 deletions
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17
include/llvm/ADT/APFloat.h
View File

@ -491,6 +491,22 @@ public:
/// return true.
bool getExactInverse(APFloat *inv) const;
/// \brief Returns the exponent of the internal representation of the APFloat.
///
/// Because the radix of APFloat is 2, this is equivalent to floor(log2(x)).
friend APFloat logb(const APFloat &Arg) {
if (Arg.isZero() || Arg.isNaN())
return Arg;
if (Arg.isInfinity())
return APFloat::getInf(Arg.getSemantics());
APFloat Result(Arg.getSemantics(), std::abs(Arg.exponent));
if (Arg.exponent < 0)
Result.changeSign();
return Result;
}
private:
/// \name Simple Queries
@ -617,6 +633,7 @@ private:
/// This additional declaration is required in order to compile LLVM with IBM
/// xlC compiler.
hash_code hash_value(const APFloat &Arg);
} // namespace llvm
#endif // LLVM_ADT_APFLOAT_H

51
unittests/ADT/APFloatTest.cpp
View File

@ -2691,4 +2691,55 @@ TEST(APFloatTest, operatorOverloads) {
EXPECT_TRUE(Two.bitwiseIsEqual(One * Two));
EXPECT_TRUE(One.bitwiseIsEqual(Two / Two));
}
TEST(APFloatTest, logb) {
EXPECT_TRUE(
APFloat(APFloat::IEEEsingle, "0x0p+0")
.bitwiseIsEqual(logb(APFloat(APFloat::IEEEsingle, "0x1p+0"))));
EXPECT_TRUE(
APFloat(APFloat::IEEEsingle, "0x0p+0")
.bitwiseIsEqual(logb(APFloat(APFloat::IEEEsingle, "-0x1p+0"))));
EXPECT_TRUE(
APFloat(APFloat::IEEEsingle, "0x2Ap+0")
.bitwiseIsEqual(logb(APFloat(APFloat::IEEEsingle, "0x1p+42"))));
EXPECT_TRUE(
APFloat(APFloat::IEEEsingle, "-0x2Ap+0")
.bitwiseIsEqual(logb(APFloat(APFloat::IEEEsingle, "0x1p-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 QNaN = APFloat::getNaN(APFloat::IEEEsingle, false);
APFloat SNaN = APFloat::getSNaN(APFloat::IEEEsingle, false);
EXPECT_TRUE(PInf.bitwiseIsEqual(logb(PInf)));
EXPECT_TRUE(PInf.bitwiseIsEqual(logb(MInf)));
EXPECT_TRUE(PZero.bitwiseIsEqual(logb(PZero)));
EXPECT_TRUE(MZero.bitwiseIsEqual(logb(MZero)));
EXPECT_TRUE(QNaN.bitwiseIsEqual(logb(QNaN)));
EXPECT_TRUE(SNaN.bitwiseIsEqual(logb(SNaN)));
APFloat PLargestValue = APFloat::getLargest(APFloat::IEEEsingle, false);
APFloat MLargestValue = APFloat::getLargest(APFloat::IEEEsingle, true);
APFloat PSmallestValue = APFloat::getSmallest(APFloat::IEEEsingle, false);
APFloat MSmallestValue = APFloat::getSmallest(APFloat::IEEEsingle, true);
APFloat PSmallestNormalized =
APFloat::getSmallestNormalized(APFloat::IEEEsingle, false);
APFloat MSmallestNormalized =
APFloat::getSmallestNormalized(APFloat::IEEEsingle, true);
EXPECT_TRUE(
APFloat(APFloat::IEEEsingle, "0x7Fp+0").bitwiseIsEqual(logb(PLargestValue)));
EXPECT_TRUE(
APFloat(APFloat::IEEEsingle, "0x7Fp+0").bitwiseIsEqual(logb(MLargestValue)));
EXPECT_TRUE(
APFloat(APFloat::IEEEsingle, "-0x7Ep+0").bitwiseIsEqual(logb(PSmallestValue)));
EXPECT_TRUE(
APFloat(APFloat::IEEEsingle, "-0x7Ep+0").bitwiseIsEqual(logb(MSmallestValue)));
EXPECT_TRUE(APFloat(APFloat::IEEEsingle, "-0x7Ep+0")
.bitwiseIsEqual(logb(PSmallestNormalized)));
EXPECT_TRUE(APFloat(APFloat::IEEEsingle, "-0x7Ep+0")
.bitwiseIsEqual(logb(MSmallestNormalized)));
}
}