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After some discussion with djg, teach SmallVector to grow from a zero

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capacity and remove the workaround in SmallVector<T,0>.  There are some
theoretical benefits to a N->2N+1 growth policy anyway.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112870 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
John McCall 2010-09-02 21:55:03 +00:00
parent 5594560766
commit 2a9a2dba4c
2 changed files with 7 additions and 18 deletions
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23
include/llvm/ADT/SmallVector.h
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@ -206,7 +206,7 @@ template <typename T, bool isPodLike>
void SmallVectorTemplateBase<T, isPodLike>::grow(size_t MinSize) {
size_t CurCapacity = this->capacity();
size_t CurSize = this->size();
size_t NewCapacity = 2*CurCapacity;
size_t NewCapacity = 2*CurCapacity + 1; // Always grow, even from zero.
if (NewCapacity < MinSize)
NewCapacity = MinSize;
T *NewElts = static_cast<T*>(malloc(NewCapacity*sizeof(T)));
@ -712,38 +712,27 @@ public:
/// members are required.
template <typename T>
class SmallVector<T,0> : public SmallVectorImpl<T> {
// SmallVector doesn't like growing from zero capacity. As a
// temporary workaround, avoid changing the growth algorithm by
// forcing capacity to be at least 1 in the constructors.
public:
SmallVector() : SmallVectorImpl<T>(0) {
this->reserve(1); // workaround
}
SmallVector() : SmallVectorImpl<T>(0) {}
explicit SmallVector(unsigned Size, const T &Value = T())
: SmallVectorImpl<T>(0) {
this->reserve(Size ? Size : 1); // workaround
this->reserve(Size);
while (Size--)
this->push_back(Value);
}
template<typename ItTy>
SmallVector(ItTy S, ItTy E) : SmallVectorImpl<T>(0) {
if (S == E) this->reserve(1); // workaround
this->append(S, E);
}
SmallVector(const SmallVector &RHS) : SmallVectorImpl<T>(0) {
if (!RHS.empty())
SmallVectorImpl<T>::operator=(RHS);
else
this->reserve(1); // workaround
SmallVectorImpl<T>::operator=(RHS);
}
const SmallVector &operator=(const SmallVector &RHS) {
SmallVectorImpl<T>::operator=(RHS);
return *this;
SmallVector &operator=(const SmallVectorImpl<T> &RHS) {
return SmallVectorImpl<T>::operator=(RHS);
}
};

2
lib/Support/SmallVector.cpp
View File

@ -18,7 +18,7 @@ using namespace llvm;
/// on POD-like datatypes and is out of line to reduce code duplication.
void SmallVectorBase::grow_pod(size_t MinSizeInBytes, size_t TSize) {
size_t CurSizeBytes = size_in_bytes();
size_t NewCapacityInBytes = 2 * capacity_in_bytes();
size_t NewCapacityInBytes = 2 * capacity_in_bytes() + TSize; // Always grow.
if (NewCapacityInBytes < MinSizeInBytes)
NewCapacityInBytes = MinSizeInBytes;