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[ADT] Implement llvm::bsearch() with std::partition_point()

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Summary:
Delete the begin-end form because the standard std::partition_point
can be easily used as a replacement.

The ranges-style llvm::bsearch will be renamed to llvm::partition_point
in the next clean-up patch.

The name "bsearch" doesn't meet people's expectation because in C:

> If two or more members compare equal, which member is returned is unspecified.

Reviewed By: sammccall

Differential Revision: https://reviews.llvm.org/D63718

llvm-svn: 364719
This commit is contained in:
Fangrui Song 2019-06-30 09:17:59 +00:00
parent ff0bc8f8ac
commit 9b1c36c2d7
3 changed files with 7 additions and 49 deletions
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39
include/llvm/ADT/STLExtras.h
View File

@ -1322,44 +1322,13 @@ void stable_sort(R &&Range, Compare C) {
std::stable_sort(adl_begin(Range), adl_end(Range), C);
}
/// Binary search for the first index where a predicate is true.
/// Returns the first I in [Lo, Hi) where C(I) is true, or Hi if it never is.
/// Requires that C is always false below some limit, and always true above it.
///
/// Example:
/// size_t DawnModernEra = bsearch(1776, 2050, [](size_t Year){
/// return Presidents.for(Year).twitterHandle() != None;
/// });
///
/// Note the return value differs from std::binary_search!
template <typename Predicate>
size_t bsearch(size_t Lo, size_t Hi, Predicate P) {
while (Lo != Hi) {
assert(Hi > Lo);
size_t Mid = Lo + (Hi - Lo) / 2;
if (P(Mid))
Hi = Mid;
else
Lo = Mid + 1;
}
return Hi;
}
/// Binary search for the first iterator where a predicate is true.
/// Returns the first I in [Lo, Hi) where C(*I) is true, or Hi if it never is.
/// Requires that C is always false below some limit, and always true above it.
template <typename It, typename Predicate,
typename Val = decltype(*std::declval<It>())>
It bsearch(It Lo, It Hi, Predicate P) {
return std::lower_bound(Lo, Hi, 0u,
[&](const Val &V, unsigned) { return !P(V); });
}
/// Binary search for the first iterator in a range where a predicate is true.
/// Requires that C is always false below some limit, and always true above it.
template <typename R, typename Predicate>
template <typename R, typename Predicate,
typename Val = decltype(*adl_begin(std::declval<R>()))>
auto bsearch(R &&Range, Predicate P) -> decltype(adl_begin(Range)) {
return bsearch(adl_begin(Range), adl_end(Range), P);
return std::partition_point(adl_begin(Range), adl_end(Range),
[&](const Val &V) { return !P(V); });
}
/// Wrapper function around std::equal to detect if all elements

5
include/llvm/CodeGen/SlotIndexes.h
View File

@ -492,8 +492,9 @@ class raw_ostream;
/// Move iterator to the next IdxMBBPair where the SlotIndex is greater or
/// equal to \p To.
MBBIndexIterator advanceMBBIndex(MBBIndexIterator I, SlotIndex To) const {
return llvm::bsearch(I, idx2MBBMap.end(),
[=](const IdxMBBPair &IM) { return To <= IM.first; });
return std::partition_point(
I, idx2MBBMap.end(),
[=](const IdxMBBPair &IM) { return IM.first < To; });
}
/// Get an iterator pointing to the IdxMBBPair with the biggest SlotIndex

12
unittests/ADT/STLExtrasTest.cpp
View File

@ -470,19 +470,7 @@ TEST(STLExtrasTest, to_address) {
}
TEST(STLExtrasTest, bsearch) {
// Integer version.
EXPECT_EQ(7u, bsearch(5, 10, [](unsigned X) { return X >= 7; }));
EXPECT_EQ(5u, bsearch(5, 10, [](unsigned X) { return X >= 1; }));
EXPECT_EQ(10u, bsearch(5, 10, [](unsigned X) { return X >= 50; }));
// Iterator version.
std::vector<int> V = {1, 3, 5, 7, 9};
EXPECT_EQ(V.begin() + 3,
bsearch(V.begin(), V.end(), [](unsigned X) { return X >= 7; }));
EXPECT_EQ(V.begin(),
bsearch(V.begin(), V.end(), [](unsigned X) { return X >= 1; }));
EXPECT_EQ(V.end(),
bsearch(V.begin(), V.end(), [](unsigned X) { return X >= 50; }));
// Range version.
EXPECT_EQ(V.begin() + 3, bsearch(V, [](unsigned X) { return X >= 7; }));