llvm-6502/lib/VMCore/Dominators.cpp
Chris Lattner 2fbfdcffd3 Change references to the Method class to be references to the Function
class.  The Method class is obsolete (renamed) and all references to it
are being converted over to Function.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@2144 91177308-0d34-0410-b5e6-96231b3b80d8
2002-04-07 20:49:59 +00:00

398 lines
15 KiB
C++

//===- DominatorSet.cpp - Dominator Set Calculation --------------*- C++ -*--=//
//
// This file provides a simple class to calculate the dominator set of a
// function.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/Dominators.h"
#include "llvm/Transforms/UnifyMethodExitNodes.h"
#include "llvm/Function.h"
#include "llvm/Support/CFG.h"
#include "Support/DepthFirstIterator.h"
#include "Support/STLExtras.h"
#include "Support/SetOperations.h"
#include <algorithm>
using std::set;
//===----------------------------------------------------------------------===//
// DominatorSet Implementation
//===----------------------------------------------------------------------===//
AnalysisID cfg::DominatorSet::ID(AnalysisID::create<cfg::DominatorSet>());
AnalysisID cfg::DominatorSet::PostDomID(AnalysisID::create<cfg::DominatorSet>());
bool cfg::DominatorSet::runOnMethod(Function *F) {
Doms.clear(); // Reset from the last time we were run...
if (isPostDominator())
calcPostDominatorSet(F);
else
calcForwardDominatorSet(F);
return false;
}
// calcForwardDominatorSet - This method calculates the forward dominator sets
// for the specified function.
//
void cfg::DominatorSet::calcForwardDominatorSet(Function *M) {
Root = M->getEntryNode();
assert(pred_begin(Root) == pred_end(Root) &&
"Root node has predecessors in function!");
bool Changed;
do {
Changed = false;
DomSetType WorkingSet;
df_iterator<Function*> It = df_begin(M), End = df_end(M);
for ( ; It != End; ++It) {
const BasicBlock *BB = *It;
pred_const_iterator PI = pred_begin(BB), PEnd = pred_end(BB);
if (PI != PEnd) { // Is there SOME predecessor?
// Loop until we get to a predecessor that has had it's dom set filled
// in at least once. We are guaranteed to have this because we are
// traversing the graph in DFO and have handled start nodes specially.
//
while (Doms[*PI].size() == 0) ++PI;
WorkingSet = Doms[*PI];
for (++PI; PI != PEnd; ++PI) { // Intersect all of the predecessor sets
DomSetType &PredSet = Doms[*PI];
if (PredSet.size())
set_intersect(WorkingSet, PredSet);
}
}
WorkingSet.insert(BB); // A block always dominates itself
DomSetType &BBSet = Doms[BB];
if (BBSet != WorkingSet) {
BBSet.swap(WorkingSet); // Constant time operation!
Changed = true; // The sets changed.
}
WorkingSet.clear(); // Clear out the set for next iteration
}
} while (Changed);
}
// Postdominator set constructor. This ctor converts the specified function to
// only have a single exit node (return stmt), then calculates the post
// dominance sets for the function.
//
void cfg::DominatorSet::calcPostDominatorSet(Function *M) {
// Since we require that the unify all exit nodes pass has been run, we know
// that there can be at most one return instruction in the function left.
// Get it.
//
Root = getAnalysis<UnifyMethodExitNodes>().getExitNode();
if (Root == 0) { // No exit node for the function? Postdomsets are all empty
for (Function::const_iterator MI = M->begin(), ME = M->end(); MI!=ME; ++MI)
Doms[*MI] = DomSetType();
return;
}
bool Changed;
do {
Changed = false;
set<const BasicBlock*> Visited;
DomSetType WorkingSet;
idf_iterator<BasicBlock*> It = idf_begin(Root), End = idf_end(Root);
for ( ; It != End; ++It) {
const BasicBlock *BB = *It;
succ_const_iterator PI = succ_begin(BB), PEnd = succ_end(BB);
if (PI != PEnd) { // Is there SOME predecessor?
// Loop until we get to a successor that has had it's dom set filled
// in at least once. We are guaranteed to have this because we are
// traversing the graph in DFO and have handled start nodes specially.
//
while (Doms[*PI].size() == 0) ++PI;
WorkingSet = Doms[*PI];
for (++PI; PI != PEnd; ++PI) { // Intersect all of the successor sets
DomSetType &PredSet = Doms[*PI];
if (PredSet.size())
set_intersect(WorkingSet, PredSet);
}
}
WorkingSet.insert(BB); // A block always dominates itself
DomSetType &BBSet = Doms[BB];
if (BBSet != WorkingSet) {
BBSet.swap(WorkingSet); // Constant time operation!
Changed = true; // The sets changed.
}
WorkingSet.clear(); // Clear out the set for next iteration
}
} while (Changed);
}
// getAnalysisUsageInfo - This obviously provides a dominator set, but it also
// uses the UnifyMethodExitNodes pass if building post-dominators
//
void cfg::DominatorSet::getAnalysisUsageInfo(Pass::AnalysisSet &Requires,
Pass::AnalysisSet &Destroyed,
Pass::AnalysisSet &Provided) {
if (isPostDominator()) {
Provided.push_back(PostDomID);
Requires.push_back(UnifyMethodExitNodes::ID);
} else {
Provided.push_back(ID);
}
}
//===----------------------------------------------------------------------===//
// ImmediateDominators Implementation
//===----------------------------------------------------------------------===//
AnalysisID cfg::ImmediateDominators::ID(AnalysisID::create<cfg::ImmediateDominators>());
AnalysisID cfg::ImmediateDominators::PostDomID(AnalysisID::create<cfg::ImmediateDominators>());
// calcIDoms - Calculate the immediate dominator mapping, given a set of
// dominators for every basic block.
void cfg::ImmediateDominators::calcIDoms(const DominatorSet &DS) {
// Loop over all of the nodes that have dominators... figuring out the IDOM
// for each node...
//
for (DominatorSet::const_iterator DI = DS.begin(), DEnd = DS.end();
DI != DEnd; ++DI) {
const BasicBlock *BB = DI->first;
const DominatorSet::DomSetType &Dominators = DI->second;
unsigned DomSetSize = Dominators.size();
if (DomSetSize == 1) continue; // Root node... IDom = null
// Loop over all dominators of this node. This corresponds to looping over
// nodes in the dominator chain, looking for a node whose dominator set is
// equal to the current nodes, except that the current node does not exist
// in it. This means that it is one level higher in the dom chain than the
// current node, and it is our idom!
//
DominatorSet::DomSetType::const_iterator I = Dominators.begin();
DominatorSet::DomSetType::const_iterator End = Dominators.end();
for (; I != End; ++I) { // Iterate over dominators...
// All of our dominators should form a chain, where the number of elements
// in the dominator set indicates what level the node is at in the chain.
// We want the node immediately above us, so it will have an identical
// dominator set, except that BB will not dominate it... therefore it's
// dominator set size will be one less than BB's...
//
if (DS.getDominators(*I).size() == DomSetSize - 1) {
IDoms[BB] = *I;
break;
}
}
}
}
//===----------------------------------------------------------------------===//
// DominatorTree Implementation
//===----------------------------------------------------------------------===//
AnalysisID cfg::DominatorTree::ID(AnalysisID::create<cfg::DominatorTree>());
AnalysisID cfg::DominatorTree::PostDomID(AnalysisID::create<cfg::DominatorTree>());
// DominatorTree::reset - Free all of the tree node memory.
//
void cfg::DominatorTree::reset() {
for (NodeMapType::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I)
delete I->second;
Nodes.clear();
}
#if 0
// Given immediate dominators, we can also calculate the dominator tree
cfg::DominatorTree::DominatorTree(const ImmediateDominators &IDoms)
: DominatorBase(IDoms.getRoot()) {
const Function *M = Root->getParent();
Nodes[Root] = new Node(Root, 0); // Add a node for the root...
// Iterate over all nodes in depth first order...
for (df_iterator<const Function*> I = df_begin(M), E = df_end(M); I!=E; ++I) {
const BasicBlock *BB = *I, *IDom = IDoms[*I];
if (IDom != 0) { // Ignore the root node and other nasty nodes
// We know that the immediate dominator should already have a node,
// because we are traversing the CFG in depth first order!
//
assert(Nodes[IDom] && "No node for IDOM?");
Node *IDomNode = Nodes[IDom];
// Add a new tree node for this BasicBlock, and link it as a child of
// IDomNode
Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
}
}
}
#endif
void cfg::DominatorTree::calculate(const DominatorSet &DS) {
Nodes[Root] = new Node(Root, 0); // Add a node for the root...
if (!isPostDominator()) {
// Iterate over all nodes in depth first order...
for (df_iterator<BasicBlock*> I = df_begin(Root), E = df_end(Root);
I != E; ++I) {
const BasicBlock *BB = *I;
const DominatorSet::DomSetType &Dominators = DS.getDominators(BB);
unsigned DomSetSize = Dominators.size();
if (DomSetSize == 1) continue; // Root node... IDom = null
// Loop over all dominators of this node. This corresponds to looping over
// nodes in the dominator chain, looking for a node whose dominator set is
// equal to the current nodes, except that the current node does not exist
// in it. This means that it is one level higher in the dom chain than the
// current node, and it is our idom! We know that we have already added
// a DominatorTree node for our idom, because the idom must be a
// predecessor in the depth first order that we are iterating through the
// function.
//
DominatorSet::DomSetType::const_iterator I = Dominators.begin();
DominatorSet::DomSetType::const_iterator End = Dominators.end();
for (; I != End; ++I) { // Iterate over dominators...
// All of our dominators should form a chain, where the number of
// elements in the dominator set indicates what level the node is at in
// the chain. We want the node immediately above us, so it will have
// an identical dominator set, except that BB will not dominate it...
// therefore it's dominator set size will be one less than BB's...
//
if (DS.getDominators(*I).size() == DomSetSize - 1) {
// We know that the immediate dominator should already have a node,
// because we are traversing the CFG in depth first order!
//
Node *IDomNode = Nodes[*I];
assert(IDomNode && "No node for IDOM?");
// Add a new tree node for this BasicBlock, and link it as a child of
// IDomNode
Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
break;
}
}
}
} else if (Root) {
// Iterate over all nodes in depth first order...
for (idf_iterator<BasicBlock*> I = idf_begin(Root), E = idf_end(Root);
I != E; ++I) {
const BasicBlock *BB = *I;
const DominatorSet::DomSetType &Dominators = DS.getDominators(BB);
unsigned DomSetSize = Dominators.size();
if (DomSetSize == 1) continue; // Root node... IDom = null
// Loop over all dominators of this node. This corresponds to looping
// over nodes in the dominator chain, looking for a node whose dominator
// set is equal to the current nodes, except that the current node does
// not exist in it. This means that it is one level higher in the dom
// chain than the current node, and it is our idom! We know that we have
// already added a DominatorTree node for our idom, because the idom must
// be a predecessor in the depth first order that we are iterating through
// the function.
//
DominatorSet::DomSetType::const_iterator I = Dominators.begin();
DominatorSet::DomSetType::const_iterator End = Dominators.end();
for (; I != End; ++I) { // Iterate over dominators...
// All of our dominators should form a chain, where the number
// of elements in the dominator set indicates what level the
// node is at in the chain. We want the node immediately
// above us, so it will have an identical dominator set,
// except that BB will not dominate it... therefore it's
// dominator set size will be one less than BB's...
//
if (DS.getDominators(*I).size() == DomSetSize - 1) {
// We know that the immediate dominator should already have a node,
// because we are traversing the CFG in depth first order!
//
Node *IDomNode = Nodes[*I];
assert(IDomNode && "No node for IDOM?");
// Add a new tree node for this BasicBlock, and link it as a child of
// IDomNode
Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
break;
}
}
}
}
}
//===----------------------------------------------------------------------===//
// DominanceFrontier Implementation
//===----------------------------------------------------------------------===//
AnalysisID cfg::DominanceFrontier::ID(AnalysisID::create<cfg::DominanceFrontier>());
AnalysisID cfg::DominanceFrontier::PostDomID(AnalysisID::create<cfg::DominanceFrontier>());
const cfg::DominanceFrontier::DomSetType &
cfg::DominanceFrontier::calcDomFrontier(const DominatorTree &DT,
const DominatorTree::Node *Node) {
// Loop over CFG successors to calculate DFlocal[Node]
const BasicBlock *BB = Node->getNode();
DomSetType &S = Frontiers[BB]; // The new set to fill in...
for (succ_const_iterator SI = succ_begin(BB), SE = succ_end(BB);
SI != SE; ++SI) {
// Does Node immediately dominate this successor?
if (DT[*SI]->getIDom() != Node)
S.insert(*SI);
}
// At this point, S is DFlocal. Now we union in DFup's of our children...
// Loop through and visit the nodes that Node immediately dominates (Node's
// children in the IDomTree)
//
for (DominatorTree::Node::const_iterator NI = Node->begin(), NE = Node->end();
NI != NE; ++NI) {
DominatorTree::Node *IDominee = *NI;
const DomSetType &ChildDF = calcDomFrontier(DT, IDominee);
DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
for (; CDFI != CDFE; ++CDFI) {
if (!Node->dominates(DT[*CDFI]))
S.insert(*CDFI);
}
}
return S;
}
const cfg::DominanceFrontier::DomSetType &
cfg::DominanceFrontier::calcPostDomFrontier(const DominatorTree &DT,
const DominatorTree::Node *Node) {
// Loop over CFG successors to calculate DFlocal[Node]
const BasicBlock *BB = Node->getNode();
DomSetType &S = Frontiers[BB]; // The new set to fill in...
if (!Root) return S;
for (pred_const_iterator SI = pred_begin(BB), SE = pred_end(BB);
SI != SE; ++SI) {
// Does Node immediately dominate this predeccessor?
if (DT[*SI]->getIDom() != Node)
S.insert(*SI);
}
// At this point, S is DFlocal. Now we union in DFup's of our children...
// Loop through and visit the nodes that Node immediately dominates (Node's
// children in the IDomTree)
//
for (DominatorTree::Node::const_iterator NI = Node->begin(), NE = Node->end();
NI != NE; ++NI) {
DominatorTree::Node *IDominee = *NI;
const DomSetType &ChildDF = calcPostDomFrontier(DT, IDominee);
DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
for (; CDFI != CDFE; ++CDFI) {
if (!Node->dominates(DT[*CDFI]))
S.insert(*CDFI);
}
}
return S;
}