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Support: Add BranchProbability::scale() and ::scaleByInverse()

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Add API to `BranchProbability` for scaling big integers.  Next job is to
rip the logic out of `BlockMass` and `BlockFrequency`.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207544 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan P. N. Exon Smith
2014-04-29 16:15:35 +00:00
parent f90262a09d
commit 048f520b91
3 changed files with 139 additions and 0 deletions
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68
unittests/Support/BranchProbabilityTest.cpp
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@ -87,4 +87,72 @@ TEST(BranchProbabilityTest, getCompl) {
EXPECT_EQ(BP::getOne(), BP(0, 7).getCompl());
}
TEST(BranchProbabilityTest, scale) {
// Multiply by 1.0.
EXPECT_EQ(UINT64_MAX, BP(1, 1).scale(UINT64_MAX));
EXPECT_EQ(UINT64_MAX, BP(7, 7).scale(UINT64_MAX));
EXPECT_EQ(UINT32_MAX, BP(1, 1).scale(UINT32_MAX));
EXPECT_EQ(UINT32_MAX, BP(7, 7).scale(UINT32_MAX));
EXPECT_EQ(0u, BP(1, 1).scale(0));
EXPECT_EQ(0u, BP(7, 7).scale(0));
// Multiply by 0.0.
EXPECT_EQ(0u, BP(0, 1).scale(UINT64_MAX));
EXPECT_EQ(0u, BP(0, 1).scale(UINT64_MAX));
EXPECT_EQ(0u, BP(0, 1).scale(0));
auto Two63 = UINT64_C(1) << 63;
auto Two31 = UINT64_C(1) << 31;
// Multiply by 0.5.
EXPECT_EQ(Two63 - 1, BP(1, 2).scale(UINT64_MAX));
// Big fractions.
EXPECT_EQ(1u, BP(Two31, UINT32_MAX).scale(2));
EXPECT_EQ(Two31, BP(Two31, UINT32_MAX).scale(Two31 * 2));
EXPECT_EQ(Two63 + Two31, BP(Two31, UINT32_MAX).scale(UINT64_MAX));
// High precision.
EXPECT_EQ(UINT64_C(9223372047592194055),
BP(Two31 + 1, UINT32_MAX - 2).scale(UINT64_MAX));
}
TEST(BranchProbabilityTest, scaleByInverse) {
// Divide by 1.0.
EXPECT_EQ(UINT64_MAX, BP(1, 1).scaleByInverse(UINT64_MAX));
EXPECT_EQ(UINT64_MAX, BP(7, 7).scaleByInverse(UINT64_MAX));
EXPECT_EQ(UINT32_MAX, BP(1, 1).scaleByInverse(UINT32_MAX));
EXPECT_EQ(UINT32_MAX, BP(7, 7).scaleByInverse(UINT32_MAX));
EXPECT_EQ(0u, BP(1, 1).scaleByInverse(0));
EXPECT_EQ(0u, BP(7, 7).scaleByInverse(0));
// Divide by something very small.
EXPECT_EQ(UINT64_MAX, BP(1, UINT32_MAX).scaleByInverse(UINT64_MAX));
EXPECT_EQ(uint64_t(UINT32_MAX) * UINT32_MAX,
BP(1, UINT32_MAX).scaleByInverse(UINT32_MAX));
EXPECT_EQ(UINT32_MAX, BP(1, UINT32_MAX).scaleByInverse(1));
auto Two63 = UINT64_C(1) << 63;
auto Two31 = UINT64_C(1) << 31;
// Divide by 0.5.
EXPECT_EQ(UINT64_MAX - 1, BP(1, 2).scaleByInverse(Two63 - 1));
EXPECT_EQ(UINT64_MAX, BP(1, 2).scaleByInverse(Two63));
// Big fractions.
EXPECT_EQ(1u, BP(Two31, UINT32_MAX).scaleByInverse(1));
EXPECT_EQ(2u, BP(Two31 - 1, UINT32_MAX).scaleByInverse(1));
EXPECT_EQ(Two31 * 2 - 1, BP(Two31, UINT32_MAX).scaleByInverse(Two31));
EXPECT_EQ(Two31 * 2 + 1, BP(Two31 - 1, UINT32_MAX).scaleByInverse(Two31));
EXPECT_EQ(UINT64_MAX, BP(Two31, UINT32_MAX).scaleByInverse(Two63 + Two31));
// High precision. The exact answers to these are close to the successors of
// the floor. If we were rounding, these would round up.
EXPECT_EQ(UINT64_C(18446744065119617030),
BP(Two31 + 2, UINT32_MAX - 2)
.scaleByInverse(UINT64_C(9223372047592194055)));
EXPECT_EQ(UINT64_C(18446744065119617026),
BP(Two31 + 1, UINT32_MAX).scaleByInverse(Two63 + Two31));
}
}