implement SmallPtrSet::erase
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@33581 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/llvm/ADT/SmallPtrSet.h b/include/llvm/ADT/SmallPtrSet.h
index d2a68ff..b9f7b1f 100644
--- a/include/llvm/ADT/SmallPtrSet.h
+++ b/include/llvm/ADT/SmallPtrSet.h
@@ -67,8 +67,6 @@
delete[] CurArray;
}
- bool isSmall() const { return CurArray == &SmallArray[0]; }
-
static void *getTombstoneMarker() { return reinterpret_cast<void*>(-2); }
static void *getEmptyMarker() {
// Note that -1 is chosen to make clear() efficiently implementable with
@@ -86,6 +84,10 @@
/// was already in the set.
bool insert(void *Ptr);
+ /// erase - If the set contains the specified pointer, remove it and return
+ /// true, otherwise return false.
+ bool erase(void *Ptr);
+
bool count(void *Ptr) const {
if (isSmall()) {
// Linear search for the item.
@@ -101,6 +103,8 @@
}
private:
+ bool isSmall() const { return CurArray == &SmallArray[0]; }
+
unsigned Hash(void *Ptr) const {
return ((uintptr_t)Ptr >> 4) & (CurArraySize-1);
}
@@ -188,7 +192,10 @@
};
-/// SmallPtrSet - This class implements
+/// SmallPtrSet - This class implements a set which is optimizer for holding
+/// SmallSize or less elements. This internally rounds up SmallSize to the next
+/// power of two if it is not already a power of two. See the comments above
+/// SmallPtrSetImpl for details of the algorithm.
template<class PtrType, unsigned SmallSize>
class SmallPtrSet : public SmallPtrSetImpl {
// Make sure that SmallSize is a power of two, round up if not.
diff --git a/lib/Support/SmallPtrSet.cpp b/lib/Support/SmallPtrSet.cpp
index 48552a5..1eea727 100644
--- a/lib/Support/SmallPtrSet.cpp
+++ b/lib/Support/SmallPtrSet.cpp
@@ -45,6 +45,33 @@
return true;
}
+bool SmallPtrSetImpl::erase(void *Ptr) {
+ if (isSmall()) {
+ // Check to see if it is in the set.
+ for (void **APtr = SmallArray, **E = SmallArray+NumElements;
+ APtr != E; ++APtr)
+ if (*APtr == Ptr) {
+ // If it is in the set, move everything over, replacing this element.
+ memmove(APtr, APtr+1, sizeof(void*)*(E-APtr-1));
+ // Clear the end element.
+ E[-1] = getEmptyMarker();
+ --NumElements;
+ return false;
+ }
+
+ return false;
+ }
+
+ // Okay, we know we have space. Find a hash bucket.
+ void **Bucket = const_cast<void**>(FindBucketFor(Ptr));
+ if (*Bucket != Ptr) return false; // Not in the set?
+
+ // Set this as a tombstone.
+ *Bucket = getTombstoneMarker();
+ --NumElements;
+ return true;
+}
+
void * const *SmallPtrSetImpl::FindBucketFor(void *Ptr) const {
unsigned Bucket = Hash(Ptr);
unsigned ArraySize = CurArraySize;