llvm-6502/lib/Support/SmallPtrSet.cpp
Benjamin Kramer 42f72e2c16 Sync the __builtin_expects for our 3 quadratically probed hash table implementations.
This assumes that
  a) finding the bucket containing the value is LIKELY
  b) finding an empty bucket is LIKELY
  c) growing the table is UNLIKELY

I also switched the a) and b) cases for SmallPtrSet as we seem to use
the set mostly more for insertion than for checking existence.

In a simple benchmark consisting of 2^21 insertions of 2^20 unique
pointers into a DenseMap or SmallPtrSet a few percent speedup on average,
but nothing statistically significant.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230232 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-23 16:41:36 +00:00

339 lines
11 KiB
C++

//===- llvm/ADT/SmallPtrSet.cpp - 'Normally small' pointer set ------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the SmallPtrSet class. See SmallPtrSet.h for an
// overview of the algorithm.
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/DenseMapInfo.h"
#include "llvm/Support/MathExtras.h"
#include <algorithm>
#include <cstdlib>
using namespace llvm;
void SmallPtrSetImplBase::shrink_and_clear() {
assert(!isSmall() && "Can't shrink a small set!");
free(CurArray);
// Reduce the number of buckets.
CurArraySize = NumElements > 16 ? 1 << (Log2_32_Ceil(NumElements) + 1) : 32;
NumElements = NumTombstones = 0;
// Install the new array. Clear all the buckets to empty.
CurArray = (const void**)malloc(sizeof(void*) * CurArraySize);
assert(CurArray && "Failed to allocate memory?");
memset(CurArray, -1, CurArraySize*sizeof(void*));
}
std::pair<const void *const *, bool>
SmallPtrSetImplBase::insert_imp(const void *Ptr) {
if (isSmall()) {
// Check to see if it is already in the set.
for (const void **APtr = SmallArray, **E = SmallArray+NumElements;
APtr != E; ++APtr)
if (*APtr == Ptr)
return std::make_pair(APtr, false);
// Nope, there isn't. If we stay small, just 'pushback' now.
if (NumElements < CurArraySize) {
SmallArray[NumElements++] = Ptr;
return std::make_pair(SmallArray + (NumElements - 1), true);
}
// Otherwise, hit the big set case, which will call grow.
}
if (LLVM_UNLIKELY(NumElements * 4 >= CurArraySize * 3)) {
// If more than 3/4 of the array is full, grow.
Grow(CurArraySize < 64 ? 128 : CurArraySize*2);
} else if (LLVM_UNLIKELY(CurArraySize - (NumElements + NumTombstones) <
CurArraySize / 8)) {
// If fewer of 1/8 of the array is empty (meaning that many are filled with
// tombstones), rehash.
Grow(CurArraySize);
}
// Okay, we know we have space. Find a hash bucket.
const void **Bucket = const_cast<const void**>(FindBucketFor(Ptr));
if (*Bucket == Ptr)
return std::make_pair(Bucket, false); // Already inserted, good.
// Otherwise, insert it!
if (*Bucket == getTombstoneMarker())
--NumTombstones;
*Bucket = Ptr;
++NumElements; // Track density.
return std::make_pair(Bucket, true);
}
bool SmallPtrSetImplBase::erase_imp(const void * Ptr) {
if (isSmall()) {
// Check to see if it is in the set.
for (const void **APtr = SmallArray, **E = SmallArray+NumElements;
APtr != E; ++APtr)
if (*APtr == Ptr) {
// If it is in the set, replace this element.
*APtr = E[-1];
E[-1] = getEmptyMarker();
--NumElements;
return true;
}
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;
++NumTombstones;
return true;
}
const void * const *SmallPtrSetImplBase::FindBucketFor(const void *Ptr) const {
unsigned Bucket = DenseMapInfo<void *>::getHashValue(Ptr) & (CurArraySize-1);
unsigned ArraySize = CurArraySize;
unsigned ProbeAmt = 1;
const void *const *Array = CurArray;
const void *const *Tombstone = nullptr;
while (1) {
// If we found an empty bucket, the pointer doesn't exist in the set.
// Return a tombstone if we've seen one so far, or the empty bucket if
// not.
if (LLVM_LIKELY(Array[Bucket] == getEmptyMarker()))
return Tombstone ? Tombstone : Array+Bucket;
// Found Ptr's bucket?
if (LLVM_LIKELY(Array[Bucket] == Ptr))
return Array+Bucket;
// If this is a tombstone, remember it. If Ptr ends up not in the set, we
// prefer to return it than something that would require more probing.
if (Array[Bucket] == getTombstoneMarker() && !Tombstone)
Tombstone = Array+Bucket; // Remember the first tombstone found.
// It's a hash collision or a tombstone. Reprobe.
Bucket = (Bucket + ProbeAmt++) & (ArraySize-1);
}
}
/// Grow - Allocate a larger backing store for the buckets and move it over.
///
void SmallPtrSetImplBase::Grow(unsigned NewSize) {
// Allocate at twice as many buckets, but at least 128.
unsigned OldSize = CurArraySize;
const void **OldBuckets = CurArray;
bool WasSmall = isSmall();
// Install the new array. Clear all the buckets to empty.
CurArray = (const void**)malloc(sizeof(void*) * NewSize);
assert(CurArray && "Failed to allocate memory?");
CurArraySize = NewSize;
memset(CurArray, -1, NewSize*sizeof(void*));
// Copy over all the elements.
if (WasSmall) {
// Small sets store their elements in order.
for (const void **BucketPtr = OldBuckets, **E = OldBuckets+NumElements;
BucketPtr != E; ++BucketPtr) {
const void *Elt = *BucketPtr;
*const_cast<void**>(FindBucketFor(Elt)) = const_cast<void*>(Elt);
}
} else {
// Copy over all valid entries.
for (const void **BucketPtr = OldBuckets, **E = OldBuckets+OldSize;
BucketPtr != E; ++BucketPtr) {
// Copy over the element if it is valid.
const void *Elt = *BucketPtr;
if (Elt != getTombstoneMarker() && Elt != getEmptyMarker())
*const_cast<void**>(FindBucketFor(Elt)) = const_cast<void*>(Elt);
}
free(OldBuckets);
NumTombstones = 0;
}
}
SmallPtrSetImplBase::SmallPtrSetImplBase(const void **SmallStorage,
const SmallPtrSetImplBase& that) {
SmallArray = SmallStorage;
// If we're becoming small, prepare to insert into our stack space
if (that.isSmall()) {
CurArray = SmallArray;
// Otherwise, allocate new heap space (unless we were the same size)
} else {
CurArray = (const void**)malloc(sizeof(void*) * that.CurArraySize);
assert(CurArray && "Failed to allocate memory?");
}
// Copy over the new array size
CurArraySize = that.CurArraySize;
// Copy over the contents from the other set
memcpy(CurArray, that.CurArray, sizeof(void*)*CurArraySize);
NumElements = that.NumElements;
NumTombstones = that.NumTombstones;
}
SmallPtrSetImplBase::SmallPtrSetImplBase(const void **SmallStorage,
unsigned SmallSize,
SmallPtrSetImplBase &&that) {
SmallArray = SmallStorage;
// Copy over the basic members.
CurArraySize = that.CurArraySize;
NumElements = that.NumElements;
NumTombstones = that.NumTombstones;
// When small, just copy into our small buffer.
if (that.isSmall()) {
CurArray = SmallArray;
memcpy(CurArray, that.CurArray, sizeof(void *) * CurArraySize);
} else {
// Otherwise, we steal the large memory allocation and no copy is needed.
CurArray = that.CurArray;
that.CurArray = that.SmallArray;
}
// Make the "that" object small and empty.
that.CurArraySize = SmallSize;
assert(that.CurArray == that.SmallArray);
that.NumElements = 0;
that.NumTombstones = 0;
}
/// CopyFrom - implement operator= from a smallptrset that has the same pointer
/// type, but may have a different small size.
void SmallPtrSetImplBase::CopyFrom(const SmallPtrSetImplBase &RHS) {
assert(&RHS != this && "Self-copy should be handled by the caller.");
if (isSmall() && RHS.isSmall())
assert(CurArraySize == RHS.CurArraySize &&
"Cannot assign sets with different small sizes");
// If we're becoming small, prepare to insert into our stack space
if (RHS.isSmall()) {
if (!isSmall())
free(CurArray);
CurArray = SmallArray;
// Otherwise, allocate new heap space (unless we were the same size)
} else if (CurArraySize != RHS.CurArraySize) {
if (isSmall())
CurArray = (const void**)malloc(sizeof(void*) * RHS.CurArraySize);
else {
const void **T = (const void**)realloc(CurArray,
sizeof(void*) * RHS.CurArraySize);
if (!T)
free(CurArray);
CurArray = T;
}
assert(CurArray && "Failed to allocate memory?");
}
// Copy over the new array size
CurArraySize = RHS.CurArraySize;
// Copy over the contents from the other set
memcpy(CurArray, RHS.CurArray, sizeof(void*)*CurArraySize);
NumElements = RHS.NumElements;
NumTombstones = RHS.NumTombstones;
}
void SmallPtrSetImplBase::MoveFrom(unsigned SmallSize,
SmallPtrSetImplBase &&RHS) {
assert(&RHS != this && "Self-move should be handled by the caller.");
if (!isSmall())
free(CurArray);
if (RHS.isSmall()) {
// Copy a small RHS rather than moving.
CurArray = SmallArray;
memcpy(CurArray, RHS.CurArray, sizeof(void*)*RHS.CurArraySize);
} else {
CurArray = RHS.CurArray;
RHS.CurArray = RHS.SmallArray;
}
// Copy the rest of the trivial members.
CurArraySize = RHS.CurArraySize;
NumElements = RHS.NumElements;
NumTombstones = RHS.NumTombstones;
// Make the RHS small and empty.
RHS.CurArraySize = SmallSize;
assert(RHS.CurArray == RHS.SmallArray);
RHS.NumElements = 0;
RHS.NumTombstones = 0;
}
void SmallPtrSetImplBase::swap(SmallPtrSetImplBase &RHS) {
if (this == &RHS) return;
// We can only avoid copying elements if neither set is small.
if (!this->isSmall() && !RHS.isSmall()) {
std::swap(this->CurArray, RHS.CurArray);
std::swap(this->CurArraySize, RHS.CurArraySize);
std::swap(this->NumElements, RHS.NumElements);
std::swap(this->NumTombstones, RHS.NumTombstones);
return;
}
// FIXME: From here on we assume that both sets have the same small size.
// If only RHS is small, copy the small elements into LHS and move the pointer
// from LHS to RHS.
if (!this->isSmall() && RHS.isSmall()) {
std::copy(RHS.SmallArray, RHS.SmallArray+RHS.CurArraySize,
this->SmallArray);
std::swap(this->NumElements, RHS.NumElements);
std::swap(this->CurArraySize, RHS.CurArraySize);
RHS.CurArray = this->CurArray;
RHS.NumTombstones = this->NumTombstones;
this->CurArray = this->SmallArray;
this->NumTombstones = 0;
return;
}
// If only LHS is small, copy the small elements into RHS and move the pointer
// from RHS to LHS.
if (this->isSmall() && !RHS.isSmall()) {
std::copy(this->SmallArray, this->SmallArray+this->CurArraySize,
RHS.SmallArray);
std::swap(RHS.NumElements, this->NumElements);
std::swap(RHS.CurArraySize, this->CurArraySize);
this->CurArray = RHS.CurArray;
this->NumTombstones = RHS.NumTombstones;
RHS.CurArray = RHS.SmallArray;
RHS.NumTombstones = 0;
return;
}
// Both a small, just swap the small elements.
assert(this->isSmall() && RHS.isSmall());
assert(this->CurArraySize == RHS.CurArraySize);
std::swap_ranges(this->SmallArray, this->SmallArray+this->CurArraySize,
RHS.SmallArray);
std::swap(this->NumElements, RHS.NumElements);
}
SmallPtrSetImplBase::~SmallPtrSetImplBase() {
if (!isSmall())
free(CurArray);
}