[PATCH] D93532: [ADT] Add resize_for_overwrite method to SmallVector.
Nathan James via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Sat Dec 19 03:00:35 PST 2020
njames93 updated this revision to Diff 312924.
njames93 added a comment.
Added test case, remove format artefact.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D93532/new/
https://reviews.llvm.org/D93532
Files:
llvm/include/llvm/ADT/SmallVector.h
llvm/unittests/ADT/SmallVectorTest.cpp
Index: llvm/unittests/ADT/SmallVectorTest.cpp
===================================================================
--- llvm/unittests/ADT/SmallVectorTest.cpp
+++ llvm/unittests/ADT/SmallVectorTest.cpp
@@ -341,6 +341,31 @@
this->assertValuesInOrder(this->theVector, 3u, 77, 77, 77);
}
+TEST(SmallVectorTest, ResizeForOverwrite) {
+ {
+ // Heap allocated storage
+ SmallVector<unsigned, 0> V;
+ V.push_back(5);
+ V.pop_back();
+ V.resize_for_overwrite(V.size() + 1);
+ EXPECT_EQ(5, V.back());
+ V.pop_back();
+ V.resize(V.size() + 1);
+ EXPECT_EQ(0, V.back());
+ }
+ {
+ // Inline storage
+ SmallVector<unsigned, 2> V;
+ V.push_back(5);
+ V.pop_back();
+ V.resize_for_overwrite(V.size() + 1);
+ EXPECT_EQ(5, V.back());
+ V.pop_back();
+ V.resize(V.size() + 1);
+ EXPECT_EQ(0, V.back());
+ }
+}
+
// Overflow past fixed size.
TYPED_TEST(SmallVectorTest, OverflowTest) {
SCOPED_TRACE("OverflowTest");
Index: llvm/include/llvm/ADT/SmallVector.h
===================================================================
--- llvm/include/llvm/ADT/SmallVector.h
+++ llvm/include/llvm/ADT/SmallVector.h
@@ -460,7 +460,8 @@
this->Size = 0;
}
- void resize(size_type N) {
+private:
+ template <bool ForOverwrite> void resizeImpl(size_type N) {
if (N < this->size()) {
this->destroy_range(this->begin()+N, this->end());
this->set_size(N);
@@ -468,11 +469,20 @@
if (this->capacity() < N)
this->grow(N);
for (auto I = this->end(), E = this->begin() + N; I != E; ++I)
- new (&*I) T();
+ if (ForOverwrite)
+ new (&*I) T;
+ else
+ new (&*I) T();
this->set_size(N);
}
}
+public:
+ void resize(size_type N) { resizeImpl<false>(N); }
+
+ /// Like resize, but \ref T is POD, the new values won't be initialized.
+ void resize_for_overwrite(size_type N) { resizeImpl<true>(N); }
+
void resize(size_type N, const T &NV) {
if (N == this->size())
return;
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