diff options
| -rw-r--r-- | llvm/lib/Support/APFloat.cpp | 2 | ||||
| -rw-r--r-- | llvm/unittests/ADT/APFloatTest.cpp | 41 |
2 files changed, 42 insertions, 1 deletions
diff --git a/llvm/lib/Support/APFloat.cpp b/llvm/lib/Support/APFloat.cpp index 295b16c55e2..393ecf4784c 100644 --- a/llvm/lib/Support/APFloat.cpp +++ b/llvm/lib/Support/APFloat.cpp @@ -1823,7 +1823,7 @@ APFloat::fusedMultiplyAdd(const APFloat &multiplicand, /* If two numbers add (exactly) to zero, IEEE 754 decrees it is a positive zero unless rounding to minus infinity, except that adding two like-signed zeroes gives that zero. */ - if (category == fcZero && sign != addend.sign) + if (category == fcZero && !(fs & opUnderflow) && sign != addend.sign) sign = (rounding_mode == rmTowardNegative); } else { fs = multiplySpecials(multiplicand); diff --git a/llvm/unittests/ADT/APFloatTest.cpp b/llvm/unittests/ADT/APFloatTest.cpp index c7ec16ba803..8b82fb2f4ed 100644 --- a/llvm/unittests/ADT/APFloatTest.cpp +++ b/llvm/unittests/ADT/APFloatTest.cpp @@ -475,6 +475,47 @@ TEST(APFloatTest, FMA) { EXPECT_EQ(12.0f, f1.convertToFloat()); } + // Test for correct zero sign when answer is exactly zero. + // fma(1.0, -1.0, 1.0) -> +ve 0. + { + APFloat f1(1.0); + APFloat f2(-1.0); + APFloat f3(1.0); + f1.fusedMultiplyAdd(f2, f3, APFloat::rmNearestTiesToEven); + EXPECT_TRUE(!f1.isNegative() && f1.isZero()); + } + + // Test for correct zero sign when answer is exactly zero and rounding towards + // negative. + // fma(1.0, -1.0, 1.0) -> +ve 0. + { + APFloat f1(1.0); + APFloat f2(-1.0); + APFloat f3(1.0); + f1.fusedMultiplyAdd(f2, f3, APFloat::rmTowardNegative); + EXPECT_TRUE(f1.isNegative() && f1.isZero()); + } + + // Test for correct (in this case -ve) sign when adding like signed zeros. + // Test fma(0.0, -0.0, -0.0) -> -ve 0. + { + APFloat f1(0.0); + APFloat f2(-0.0); + APFloat f3(-0.0); + f1.fusedMultiplyAdd(f2, f3, APFloat::rmNearestTiesToEven); + EXPECT_TRUE(f1.isNegative() && f1.isZero()); + } + + // Test -ve sign preservation when small negative results underflow. + { + APFloat f1(APFloat::IEEEdouble, "-0x1p-1074"); + APFloat f2(APFloat::IEEEdouble, "+0x1p-1074"); + APFloat f3(0.0); + f1.fusedMultiplyAdd(f2, f3, APFloat::rmNearestTiesToEven); + EXPECT_TRUE(f1.isNegative() && f1.isZero()); + } + + // Test x87 extended precision case from http://llvm.org/PR20728. { APFloat M1(APFloat::x87DoubleExtended, 1.0); APFloat M2(APFloat::x87DoubleExtended, 1.0); |
