llvm-6502/lib/Support/FoldingSet.cpp
Chris Lattner 0de4439ad1 improve comments, add an assertion
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@33750 91177308-0d34-0410-b5e6-96231b3b80d8
2007-02-01 05:33:21 +00:00

309 lines
10 KiB
C++

//===-- Support/FoldingSet.cpp - Uniquing Hash Set --------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by James M. Laskey and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements a hash set that can be used to remove duplication of
// nodes in a graph. This code was originally created by Chris Lattner for use
// with SelectionDAGCSEMap, but was isolated to provide use across the llvm code
// set.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "foldingset"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Debug.h"
#include <cassert>
using namespace llvm;
//===----------------------------------------------------------------------===//
// FoldingSetImpl::NodeID Implementation
/// Add* - Add various data types to Bit data.
///
void FoldingSetImpl::NodeID::AddPointer(const void *Ptr) {
// Note: this adds pointers to the hash using sizes and endianness that
// depend on the host. It doesn't matter however, because hashing on
// pointer values in inherently unstable. Nothing should depend on the
// ordering of nodes in the folding set.
intptr_t PtrI = (intptr_t)Ptr;
Bits.push_back(unsigned(PtrI));
if (sizeof(intptr_t) > sizeof(unsigned))
Bits.push_back(unsigned(uint64_t(PtrI) >> 32));
}
void FoldingSetImpl::NodeID::AddInteger(signed I) {
Bits.push_back(I);
}
void FoldingSetImpl::NodeID::AddInteger(unsigned I) {
Bits.push_back(I);
}
void FoldingSetImpl::NodeID::AddInteger(uint64_t I) {
Bits.push_back(unsigned(I));
Bits.push_back(unsigned(I >> 32));
}
void FoldingSetImpl::NodeID::AddFloat(float F) {
Bits.push_back(FloatToBits(F));
}
void FoldingSetImpl::NodeID::AddDouble(double D) {
AddInteger(DoubleToBits(D));
}
void FoldingSetImpl::NodeID::AddString(const std::string &String) {
unsigned Size = String.size();
Bits.push_back(Size);
if (!Size) return;
unsigned Units = Size / 4;
unsigned Pos = 0;
const unsigned *Base = (const unsigned *)String.data();
// If the string is aligned do a bulk transfer.
if (!((intptr_t)Base & 3)) {
Bits.append(Base, Base + Units);
Pos = (Units + 1) * 4;
} else {
// Otherwise do it the hard way.
for ( Pos += 4; Pos <= Size; Pos += 4) {
unsigned V = ((unsigned char)String[Pos - 4] << 24) |
((unsigned char)String[Pos - 3] << 16) |
((unsigned char)String[Pos - 2] << 8) |
(unsigned char)String[Pos - 1];
Bits.push_back(V);
}
}
// With the leftover bits.
unsigned V = 0;
// Pos will have overshot size by 4 - #bytes left over.
switch (Pos - Size) {
case 1: V = (V << 8) | (unsigned char)String[Size - 3]; // Fall thru.
case 2: V = (V << 8) | (unsigned char)String[Size - 2]; // Fall thru.
case 3: V = (V << 8) | (unsigned char)String[Size - 1]; break;
default: return; // Nothing left.
}
Bits.push_back(V);
}
/// ComputeHash - Compute a strong hash value for this NodeID, used to
/// lookup the node in the FoldingSetImpl.
unsigned FoldingSetImpl::NodeID::ComputeHash() const {
// This is adapted from SuperFastHash by Paul Hsieh.
unsigned Hash = Bits.size();
for (const unsigned *BP = &Bits[0], *E = BP+Bits.size(); BP != E; ++BP) {
unsigned Data = *BP;
Hash += Data & 0xFFFF;
unsigned Tmp = ((Data >> 16) << 11) ^ Hash;
Hash = (Hash << 16) ^ Tmp;
Hash += Hash >> 11;
}
// Force "avalanching" of final 127 bits.
Hash ^= Hash << 3;
Hash += Hash >> 5;
Hash ^= Hash << 4;
Hash += Hash >> 17;
Hash ^= Hash << 25;
Hash += Hash >> 6;
return Hash;
}
/// operator== - Used to compare two nodes to each other.
///
bool FoldingSetImpl::NodeID::operator==(const FoldingSetImpl::NodeID &RHS)const{
if (Bits.size() != RHS.Bits.size()) return false;
return memcmp(&Bits[0], &RHS.Bits[0], Bits.size()*sizeof(Bits[0])) == 0;
}
//===----------------------------------------------------------------------===//
/// Helper functions for FoldingSetImpl.
/// GetNextPtr - In order to save space, each bucket is a
/// singly-linked-list. In order to make deletion more efficient, we make
/// the list circular, so we can delete a node without computing its hash.
/// The problem with this is that the start of the hash buckets are not
/// Nodes. If NextInBucketPtr is a bucket pointer, this method returns null:
/// use GetBucketPtr when this happens.
static FoldingSetImpl::Node *GetNextPtr(void *NextInBucketPtr,
void **Buckets, unsigned NumBuckets) {
if (NextInBucketPtr >= Buckets && NextInBucketPtr < Buckets + NumBuckets)
return 0;
return static_cast<FoldingSetImpl::Node*>(NextInBucketPtr);
}
/// GetBucketPtr - Provides a casting of a bucket pointer for isNode
/// testing.
static void **GetBucketPtr(void *NextInBucketPtr) {
return static_cast<void**>(NextInBucketPtr);
}
/// GetBucketFor - Hash the specified node ID and return the hash bucket for
/// the specified ID.
static void **GetBucketFor(const FoldingSetImpl::NodeID &ID,
void **Buckets, unsigned NumBuckets) {
// NumBuckets is always a power of 2.
unsigned BucketNum = ID.ComputeHash() & (NumBuckets-1);
return Buckets + BucketNum;
}
//===----------------------------------------------------------------------===//
// FoldingSetImpl Implementation
FoldingSetImpl::FoldingSetImpl(unsigned Log2InitSize) : NumNodes(0) {
assert(5 < Log2InitSize && Log2InitSize < 32 &&
"Initial hash table size out of range");
NumBuckets = 1 << Log2InitSize;
Buckets = new void*[NumBuckets];
memset(Buckets, 0, NumBuckets*sizeof(void*));
}
FoldingSetImpl::~FoldingSetImpl() {
delete [] Buckets;
}
/// GrowHashTable - Double the size of the hash table and rehash everything.
///
void FoldingSetImpl::GrowHashTable() {
void **OldBuckets = Buckets;
unsigned OldNumBuckets = NumBuckets;
NumBuckets <<= 1;
// Reset the node count to zero: we're going to reinsert everything.
NumNodes = 0;
// Clear out new buckets.
Buckets = new void*[NumBuckets];
memset(Buckets, 0, NumBuckets*sizeof(void*));
// Walk the old buckets, rehashing nodes into their new place.
for (unsigned i = 0; i != OldNumBuckets; ++i) {
void *Probe = OldBuckets[i];
if (!Probe) continue;
while (Node *NodeInBucket = GetNextPtr(Probe, OldBuckets, OldNumBuckets)) {
// Figure out the next link, remove NodeInBucket from the old link.
Probe = NodeInBucket->getNextInBucket();
NodeInBucket->SetNextInBucket(0);
// Insert the node into the new bucket, after recomputing the hash.
NodeID ID;
GetNodeProfile(ID, NodeInBucket);
InsertNode(NodeInBucket, GetBucketFor(ID, Buckets, NumBuckets));
}
}
delete[] OldBuckets;
}
/// FindNodeOrInsertPos - Look up the node specified by ID. If it exists,
/// return it. If not, return the insertion token that will make insertion
/// faster.
FoldingSetImpl::Node *FoldingSetImpl::FindNodeOrInsertPos(const NodeID &ID,
void *&InsertPos) {
void **Bucket = GetBucketFor(ID, Buckets, NumBuckets);
void *Probe = *Bucket;
InsertPos = 0;
while (Node *NodeInBucket = GetNextPtr(Probe, Buckets, NumBuckets)) {
NodeID OtherID;
GetNodeProfile(OtherID, NodeInBucket);
if (OtherID == ID)
return NodeInBucket;
Probe = NodeInBucket->getNextInBucket();
}
// Didn't find the node, return null with the bucket as the InsertPos.
InsertPos = Bucket;
return 0;
}
/// InsertNode - Insert the specified node into the folding set, knowing that it
/// is not already in the map. InsertPos must be obtained from
/// FindNodeOrInsertPos.
void FoldingSetImpl::InsertNode(Node *N, void *InsertPos) {
assert(N->getNextInBucket() == 0);
// Do we need to grow the hashtable?
DEBUG(DOUT << "INSERT: " << N << '\n');
if (NumNodes+1 > NumBuckets*2) {
GrowHashTable();
NodeID ID;
GetNodeProfile(ID, N);
InsertPos = GetBucketFor(ID, Buckets, NumBuckets);
}
++NumNodes;
/// The insert position is actually a bucket pointer.
void **Bucket = static_cast<void**>(InsertPos);
void *Next = *Bucket;
// If this is the first insertion into this bucket, its next pointer will be
// null. Pretend as if it pointed to itself.
if (Next == 0)
Next = Bucket;
// Set the node's next pointer, and make the bucket point to the node.
N->SetNextInBucket(Next);
*Bucket = N;
}
/// RemoveNode - Remove a node from the folding set, returning true if one was
/// removed or false if the node was not in the folding set.
bool FoldingSetImpl::RemoveNode(Node *N) {
// Because each bucket is a circular list, we don't need to compute N's hash
// to remove it.
DEBUG(DOUT << "REMOVE: " << N << '\n');
void *Ptr = N->getNextInBucket();
if (Ptr == 0) return false; // Not in folding set.
--NumNodes;
N->SetNextInBucket(0);
// Remember what N originally pointed to, either a bucket or another node.
void *NodeNextPtr = Ptr;
// Chase around the list until we find the node (or bucket) which points to N.
while (true) {
if (Node *NodeInBucket = GetNextPtr(Ptr, Buckets, NumBuckets)) {
// Advance pointer.
Ptr = NodeInBucket->getNextInBucket();
// We found a node that points to N, change it to point to N's next node,
// removing N from the list.
if (Ptr == N) {
NodeInBucket->SetNextInBucket(NodeNextPtr);
return true;
}
} else {
void **Bucket = GetBucketPtr(Ptr);
Ptr = *Bucket;
// If we found that the bucket points to N, update the bucket to point to
// whatever is next.
if (Ptr == N) {
*Bucket = NodeNextPtr;
return true;
}
}
}
}
/// GetOrInsertNode - If there is an existing simple Node exactly
/// equal to the specified node, return it. Otherwise, insert 'N' and it
/// instead.
FoldingSetImpl::Node *FoldingSetImpl::GetOrInsertNode(FoldingSetImpl::Node *N) {
NodeID ID;
GetNodeProfile(ID, N);
void *IP;
if (Node *E = FindNodeOrInsertPos(ID, IP))
return E;
InsertNode(N, IP);
return N;
}