//==- llvm/CodeGen/MachineDominators.h - Machine Dom Calculation -*- C++ -*-==//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines classes mirroring those in llvm/Analysis/Dominators.h,
// but for target-specific code rather than target-independent IR.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_MACHINEDOMINATORS_H
#define LLVM_CODEGEN_MACHINEDOMINATORS_H
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBundleIterator.h"
#include "llvm/Support/GenericDomTree.h"
#include "llvm/Support/GenericDomTreeConstruction.h"
#include <cassert>
#include <memory>
namespace llvm {
class AnalysisUsage;
class MachineFunction;
class Module;
class raw_ostream;
template <>
inline void DominatorTreeBase<MachineBasicBlock, false>::addRoot(
MachineBasicBlock *MBB) {
this->Roots.push_back(MBB);
}
extern template class DomTreeNodeBase<MachineBasicBlock>;
extern template class DominatorTreeBase<MachineBasicBlock, false>; // DomTree
extern template class DominatorTreeBase<MachineBasicBlock, true>; // PostDomTree
using MachineDomTree = DomTreeBase<MachineBasicBlock>;
using MachineDomTreeNode = DomTreeNodeBase<MachineBasicBlock>;
//===-------------------------------------
/// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to
/// compute a normal dominator tree.
///
class MachineDominatorTree : public MachineFunctionPass {
/// Helper structure used to hold all the basic blocks
/// involved in the split of a critical edge.
struct CriticalEdge {
MachineBasicBlock *FromBB;
MachineBasicBlock *ToBB;
MachineBasicBlock *NewBB;
};
/// Pile up all the critical edges to be split.
/// The splitting of a critical edge is local and thus, it is possible
/// to apply several of those changes at the same time.
mutable SmallVector<CriticalEdge, 32> CriticalEdgesToSplit;
/// Remember all the basic blocks that are inserted during
/// edge splitting.
/// Invariant: NewBBs == all the basic blocks contained in the NewBB
/// field of all the elements of CriticalEdgesToSplit.
/// I.e., forall elt in CriticalEdgesToSplit, it exists BB in NewBBs
/// such as BB == elt.NewBB.
mutable SmallSet<MachineBasicBlock *, 32> NewBBs;
/// The DominatorTreeBase that is used to compute a normal dominator tree.
std::unique_ptr<MachineDomTree> DT;
/// Apply all the recorded critical edges to the DT.
/// This updates the underlying DT information in a way that uses
/// the fast query path of DT as much as possible.
///
/// \post CriticalEdgesToSplit.empty().
void applySplitCriticalEdges() const;
public:
static char ID; // Pass ID, replacement for typeid
MachineDominatorTree();
explicit MachineDominatorTree(MachineFunction &MF) : MachineFunctionPass(ID) {
calculate(MF);
}
MachineDomTree &getBase() {
if (!DT)
DT.reset(new MachineDomTree());
applySplitCriticalEdges();
return *DT;
}
void getAnalysisUsage(AnalysisUsage &AU) const override;
MachineBasicBlock *getRoot() const {
applySplitCriticalEdges();
return DT->getRoot();
}
MachineDomTreeNode *getRootNode() const {
applySplitCriticalEdges();
return DT->getRootNode();
}
bool runOnMachineFunction(MachineFunction &F) override;
void calculate(MachineFunction &F);
bool dominates(const MachineDomTreeNode *A,
const MachineDomTreeNode *B) const {
applySplitCriticalEdges();
return DT->dominates(A, B);
}
void getDescendants(MachineBasicBlock *A,
SmallVectorImpl<MachineBasicBlock *> &Result) {
applySplitCriticalEdges();
DT->getDescendants(A, Result);
}
bool dominates(const MachineBasicBlock *A, const MachineBasicBlock *B) const {
applySplitCriticalEdges();
return DT->dominates(A, B);
}
// dominates - Return true if A dominates B. This performs the
// special checks necessary if A and B are in the same basic block.
bool dominates(const MachineInstr *A, const MachineInstr *B) const {
applySplitCriticalEdges();
const MachineBasicBlock *BBA = A->getParent(), *BBB = B->getParent();
if (BBA != BBB) return DT->dominates(BBA, BBB);
// Loop through the basic block until we find A or B.
MachineBasicBlock::const_iterator I = BBA->begin();
for (; &*I != A && &*I != B; ++I)
/*empty*/ ;
return &*I == A;
}
bool properlyDominates(const MachineDomTreeNode *A,
const MachineDomTreeNode *B) const {
applySplitCriticalEdges();
return DT->properlyDominates(A, B);
}
bool properlyDominates(const MachineBasicBlock *A,
const MachineBasicBlock *B) const {
applySplitCriticalEdges();
return DT->properlyDominates(A, B);
}
/// findNearestCommonDominator - Find nearest common dominator basic block
/// for basic block A and B. If there is no such block then return NULL.
MachineBasicBlock *findNearestCommonDominator(MachineBasicBlock *A,
MachineBasicBlock *B) {
applySplitCriticalEdges();
return DT->findNearestCommonDominator(A, B);
}
MachineDomTreeNode *operator[](MachineBasicBlock *BB) const {
applySplitCriticalEdges();
return DT->getNode(BB);
}
/// getNode - return the (Post)DominatorTree node for the specified basic
/// block. This is the same as using operator[] on this class.
///
MachineDomTreeNode *getNode(MachineBasicBlock *BB) const {
applySplitCriticalEdges();
return DT->getNode(BB);
}
/// addNewBlock - Add a new node to the dominator tree information. This
/// creates a new node as a child of DomBB dominator node,linking it into
/// the children list of the immediate dominator.
MachineDomTreeNode *addNewBlock(MachineBasicBlock *BB,
MachineBasicBlock *DomBB) {
applySplitCriticalEdges();
return DT->addNewBlock(BB, DomBB);
}
/// changeImmediateDominator - This method is used to update the dominator
/// tree information when a node's immediate dominator changes.
///
void changeImmediateDominator(MachineBasicBlock *N,
MachineBasicBlock *NewIDom) {
applySplitCriticalEdges();
DT->changeImmediateDominator(N, NewIDom);
}
void changeImmediateDominator(MachineDomTreeNode *N,
MachineDomTreeNode *NewIDom) {
applySplitCriticalEdges();
DT->changeImmediateDominator(N, NewIDom);
}
/// eraseNode - Removes a node from the dominator tree. Block must not
/// dominate any other blocks. Removes node from its immediate dominator's
/// children list. Deletes dominator node associated with basic block BB.
void eraseNode(MachineBasicBlock *BB) {
applySplitCriticalEdges();
DT->eraseNode(BB);
}
/// splitBlock - BB is split and now it has one successor. Update dominator
/// tree to reflect this change.
void splitBlock(MachineBasicBlock* NewBB) {
applySplitCriticalEdges();
DT->splitBlock(NewBB);
}
/// isReachableFromEntry - Return true if A is dominated by the entry
/// block of the function containing it.
bool isReachableFromEntry(const MachineBasicBlock *A) {
applySplitCriticalEdges();
return DT->isReachableFromEntry(A);
}
void releaseMemory() override;
void verifyAnalysis() const override;
void print(raw_ostream &OS, const Module*) const override;
/// Record that the critical edge (FromBB, ToBB) has been
/// split with NewBB.
/// This is best to use this method instead of directly update the
/// underlying information, because this helps mitigating the
/// number of time the DT information is invalidated.
///
/// \note Do not use this method with regular edges.
///
/// \note To benefit from the compile time improvement incurred by this
/// method, the users of this method have to limit the queries to the DT
/// interface between two edges splitting. In other words, they have to
/// pack the splitting of critical edges as much as possible.
void recordSplitCriticalEdge(MachineBasicBlock *FromBB,
MachineBasicBlock *ToBB,
MachineBasicBlock *NewBB) {
bool Inserted = NewBBs.insert(NewBB).second;
(void)Inserted;
assert(Inserted &&
"A basic block inserted via edge splitting cannot appear twice");
CriticalEdgesToSplit.push_back({FromBB, ToBB, NewBB});
}
};
//===-------------------------------------
/// DominatorTree GraphTraits specialization so the DominatorTree can be
/// iterable by generic graph iterators.
///
template <class Node, class ChildIterator>
struct MachineDomTreeGraphTraitsBase {
using NodeRef = Node *;
using ChildIteratorType = ChildIterator;
static NodeRef getEntryNode(NodeRef N) { return N; }
static ChildIteratorType child_begin(NodeRef N) { return N->begin(); }
static ChildIteratorType child_end(NodeRef N) { return N->end(); }
};
template <class T> struct GraphTraits;
template <>
struct GraphTraits<MachineDomTreeNode *>
: public MachineDomTreeGraphTraitsBase<MachineDomTreeNode,
MachineDomTreeNode::const_iterator> {
};
template <>
struct GraphTraits<const MachineDomTreeNode *>
: public MachineDomTreeGraphTraitsBase<const MachineDomTreeNode,
MachineDomTreeNode::const_iterator> {
};
template <> struct GraphTraits<MachineDominatorTree*>
: public GraphTraits<MachineDomTreeNode *> {
static NodeRef getEntryNode(MachineDominatorTree *DT) {
return DT->getRootNode();
}
};
} // end namespace llvm
#endif // LLVM_CODEGEN_MACHINEDOMINATORS_H