Summary:
For our set/map types, count/find normally take const references.
This works well for non-pointer types, but can suck for pointer
types.
DenseSet<int *> foo;
const int *b = nullptr;
foo.count(b) does not work
but the equivalent reference version does work
(patch to fix DenseSet/DenseMap coming up)
For SmallPtrSet, you have no such option.
The following will not work right now:
SmallPtrSet<int *> foo;
const int *b = nullptr;
foo.count(b);
This makes const correctness hard in some cases.
Example:
SmallPtrSet<Instruction *> InstructionsToErase;
You can't make this SmallPtrSet<const Instruction *> because then you
can't erase the instruction. If I want to see if something is in the
set, I may only have a const Instruction *. Given that count and find
are non-mutating, this should just work.
The places in our code base that do this resort to const_cast :(.
This patch makes count and find able to be used with const Instruction
* in the above SmallPtrSet examples.
This is a bit annoying because of where C++ applies the const, so we
have to remove the pointer type from the passed-in-type and rebuild it
with const.
Reviewers: dblaikie
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D30608
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297180
91177308-0d34-0410-b5e6-
96231b3b80d8
#include "llvm/Config/abi-breaking.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/PointerLikeTypeTraits.h"
+#include "llvm/Support/type_traits.h"
#include <cassert>
#include <cstddef>
#include <cstring>
/// to avoid encoding a particular small size in the interface boundary.
template <typename PtrType>
class SmallPtrSetImpl : public SmallPtrSetImplBase {
+ using ConstPtrType = typename add_const_past_pointer<PtrType>::type;
typedef PointerLikeTypeTraits<PtrType> PtrTraits;
+ typedef PointerLikeTypeTraits<ConstPtrType> ConstPtrTraits;
protected:
// Constructors that forward to the base.
bool erase(PtrType Ptr) {
return erase_imp(PtrTraits::getAsVoidPointer(Ptr));
}
-
/// count - Return 1 if the specified pointer is in the set, 0 otherwise.
- size_type count(PtrType Ptr) const {
+ size_type count(ConstPtrType Ptr) const {
return find(Ptr) != endPtr() ? 1 : 0;
}
- iterator find(PtrType Ptr) const {
- auto *P = find_imp(PtrTraits::getAsVoidPointer(Ptr));
+ iterator find(ConstPtrType Ptr) const {
+ auto *P = find_imp(ConstPtrTraits::getAsVoidPointer(Ptr));
return iterator(P, EndPointer());
}