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| author | Benjamin Kramer <benny.kra@googlemail.com> | 2011-03-30 15:42:27 +0000 |
|---|---|---|
| committer | Benjamin Kramer <benny.kra@googlemail.com> | 2011-03-30 15:42:27 +0000 |
| commit | 2746000f4fa54e6ad00cf96910ea5772803624ed (patch) | |
| tree | bd6513967e2f459833124c1834762d983bf7b3b0 /unittests/ADT/APFloatTest.cpp | |
| parent | d01f2633b9aab6281c936da04226b46a0dde7ba9 (diff) | |
| download | llvm-2746000f4fa54e6ad00cf96910ea5772803624ed.tar.gz llvm-2746000f4fa54e6ad00cf96910ea5772803624ed.tar.bz2 llvm-2746000f4fa54e6ad00cf96910ea5772803624ed.tar.xz | |
Add APFloat::getExactInverse.
The idea is, that if an ieee 754 float is divided by a power of two, we can
turn the division into a cheaper multiplication. This function sees if we can
get an exact multiplicative inverse for a divisor and returns it if possible.
This is the hard part of PR9587.
I tested many inputs against llvm-gcc's frotend implementation of this
optimization and didn't find any difference. However, floating point is the
land of weird edge cases, so any review would be appreciated.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128545 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'unittests/ADT/APFloatTest.cpp')
| -rw-r--r-- | unittests/ADT/APFloatTest.cpp | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/unittests/ADT/APFloatTest.cpp b/unittests/ADT/APFloatTest.cpp index 964b04da47..dea4a65b88 100644 --- a/unittests/ADT/APFloatTest.cpp +++ b/unittests/ADT/APFloatTest.cpp @@ -576,4 +576,27 @@ TEST(APFloatTest, StringHexadecimalExponentDeath) { #endif #endif +TEST(APFloatTest, exactInverse) { + APFloat inv(0.0f); + + // Trivial operation. + EXPECT_TRUE(APFloat(2.0).getExactInverse(&inv)); + EXPECT_TRUE(inv.bitwiseIsEqual(APFloat(0.5))); + EXPECT_TRUE(APFloat(2.0f).getExactInverse(&inv)); + EXPECT_TRUE(inv.bitwiseIsEqual(APFloat(0.5f))); + + // FLT_MIN + EXPECT_TRUE(APFloat(1.17549435e-38f).getExactInverse(&inv)); + EXPECT_TRUE(inv.bitwiseIsEqual(APFloat(8.5070592e+37f))); + + // Large float + EXPECT_TRUE(APFloat(1.7014118e38f).getExactInverse(&inv)); + EXPECT_TRUE(inv.bitwiseIsEqual(APFloat(5.8774718e-39f))); + + // Zero + EXPECT_FALSE(APFloat(0.0).getExactInverse(0)); + // Denormalized float + EXPECT_FALSE(APFloat(1.40129846e-45f).getExactInverse(0)); +} + } |