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[ADT] Add SparseBitVector::find_last().

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Differential Revision: https://reviews.llvm.org/D28817

llvm-svn: 292288
This commit is contained in:
Zachary Turner 2017-01-17 23:09:21 +00:00
parent 279707ab7f
commit 0a3b8732fd
2 changed files with 58 additions and 0 deletions
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19
include/llvm/ADT/SparseBitVector.h
View File

@ -132,6 +132,17 @@ public:
llvm_unreachable("Illegal empty element");
}
/// find_last - Returns the index of the last set bit.
int find_last() const {
for (unsigned I = 0; I < BITWORDS_PER_ELEMENT; ++I) {
unsigned Idx = BITWORDS_PER_ELEMENT - I - 1;
if (Bits[Idx] != 0)
return Idx * BITWORD_SIZE + BITWORD_SIZE -
countLeadingZeros(Bits[Idx]) - 1;
}
llvm_unreachable("Illegal empty element");
}
/// find_next - Returns the index of the next set bit starting from the
/// "Curr" bit. Returns -1 if the next set bit is not found.
int find_next(unsigned Curr) const {
@ -768,6 +779,14 @@ public:
return (First.index() * ElementSize) + First.find_first();
}
// Return the last set bit in the bitmap. Return -1 if no bits are set.
int find_last() const {
if (Elements.empty())
return -1;
const SparseBitVectorElement<ElementSize> &Last = *(Elements.rbegin());
return (Last.index() * ElementSize) + Last.find_last();
}
// Return true if the SparseBitVector is empty
bool empty() const {
return Elements.empty();

39
unittests/ADT/SparseBitVectorTest.cpp
View File

@ -127,4 +127,43 @@ TEST(SparseBitVectorTest, SelfAssignment) {
EXPECT_TRUE(Vec.empty());
}
TEST(SparseBitVectorTest, Find) {
SparseBitVector<> Vec;
Vec.set(1);
EXPECT_EQ(1, Vec.find_first());
EXPECT_EQ(1, Vec.find_last());
Vec.set(2);
EXPECT_EQ(1, Vec.find_first());
EXPECT_EQ(2, Vec.find_last());
Vec.set(0);
Vec.set(3);
EXPECT_EQ(0, Vec.find_first());
EXPECT_EQ(3, Vec.find_last());
Vec.reset(1);
Vec.reset(0);
Vec.reset(3);
EXPECT_EQ(2, Vec.find_first());
EXPECT_EQ(2, Vec.find_last());
// Set some large bits to ensure we are pulling bits from more than just a
// single bitword.
Vec.set(500);
Vec.set(2000);
Vec.set(3000);
Vec.set(4000);
Vec.reset(2);
EXPECT_EQ(500, Vec.find_first());
EXPECT_EQ(4000, Vec.find_last());
Vec.reset(500);
Vec.reset(3000);
Vec.reset(4000);
EXPECT_EQ(2000, Vec.find_first());
EXPECT_EQ(2000, Vec.find_last());
Vec.clear();
}
}