mirror of
https://github.com/RPCS3/llvm.git
synced 2024-12-11 13:44:28 +00:00
Rework post dominator information so that we do not have to
unify all exit nodes of a function to compute post-dominance information. This does not work with functions that have both unwind and return nodes, because we cannot unify these blocks. The new implementation is better anyway. :) git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@8460 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
parent
420a8bf2b2
commit
706e61ead9
@ -5,7 +5,7 @@
|
||||
//===----------------------------------------------------------------------===//
|
||||
|
||||
#include "llvm/Analysis/PostDominators.h"
|
||||
#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
|
||||
#include "llvm/iTerminators.h"
|
||||
#include "llvm/Support/CFG.h"
|
||||
#include "Support/DepthFirstIterator.h"
|
||||
#include "Support/SetOperations.h"
|
||||
@ -23,75 +23,77 @@ B("postdomset", "Post-Dominator Set Construction", true);
|
||||
//
|
||||
bool PostDominatorSet::runOnFunction(Function &F) {
|
||||
Doms.clear(); // Reset from the last time we were run...
|
||||
// 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<UnifyFunctionExitNodes>().getExitNode();
|
||||
|
||||
if (Root == 0) { // No exit node for the function? Postdomsets are all empty
|
||||
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI)
|
||||
Doms[FI] = DomSetType();
|
||||
return false;
|
||||
// Scan the function looking for the root nodes of the post-dominance
|
||||
// relationships. These blocks end with return and unwind instructions.
|
||||
// While we are iterating over the function, we also initialize all of the
|
||||
// domsets to empty.
|
||||
Roots.clear();
|
||||
for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) {
|
||||
Doms[I]; // Initialize to empty
|
||||
|
||||
if (isa<ReturnInst>(I->getTerminator()) ||
|
||||
isa<UnwindInst>(I->getTerminator()))
|
||||
Roots.push_back(I);
|
||||
}
|
||||
|
||||
// If there are no exit nodes for the function, postdomsets are all empty.
|
||||
// This can happen if the function just contains an infinite loop, for
|
||||
// example.
|
||||
if (Roots.empty()) return false;
|
||||
|
||||
// If we have more than one root, we insert an artificial "null" exit, which
|
||||
// has "virtual edges" to each of the real exit nodes.
|
||||
if (Roots.size() > 1)
|
||||
Doms[0].insert(0);
|
||||
|
||||
bool Changed;
|
||||
do {
|
||||
Changed = false;
|
||||
|
||||
std::set<const BasicBlock*> Visited;
|
||||
DomSetType WorkingSet;
|
||||
idf_iterator<BasicBlock*> It = idf_begin(Root), End = idf_end(Root);
|
||||
for ( ; It != End; ++It) {
|
||||
BasicBlock *BB = *It;
|
||||
succ_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);
|
||||
}
|
||||
} else if (BB != Root) {
|
||||
// If this isn't the root basic block and it has no successors, it must
|
||||
// be an non-returning block. Fib a bit by saying that the root node
|
||||
// postdominates this unreachable node. This isn't exactly true,
|
||||
// because there is no path from this node to the root node, but it is
|
||||
// sorta true because any paths to the exit node would have to go
|
||||
// through this node.
|
||||
//
|
||||
// This allows for postdominator properties to be built for code that
|
||||
// doesn't return in a reasonable manner.
|
||||
//
|
||||
WorkingSet = Doms[Root];
|
||||
}
|
||||
for (unsigned i = 0, e = Roots.size(); i != e; ++i)
|
||||
for (idf_iterator<BasicBlock*> It = idf_begin(Roots[i]),
|
||||
E = idf_end(Roots[i]); It != E; ++It) {
|
||||
BasicBlock *BB = *It;
|
||||
succ_iterator SI = succ_begin(BB), SE = succ_end(BB);
|
||||
if (SI != SE) { // Is there SOME successor?
|
||||
// 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[*SI].size() == 0) ++SI;
|
||||
WorkingSet = Doms[*SI];
|
||||
|
||||
for (++SI; SI != SE; ++SI) { // Intersect all of the successor sets
|
||||
DomSetType &SuccSet = Doms[*SI];
|
||||
if (SuccSet.size())
|
||||
set_intersect(WorkingSet, SuccSet);
|
||||
}
|
||||
} else {
|
||||
// If this node has no successors, it must be one of the root nodes.
|
||||
// We will already take care of the notion that the node
|
||||
// post-dominates itself. The only thing we have to add is that if
|
||||
// there are multiple root nodes, we want to insert a special "null"
|
||||
// exit node which dominates the roots as well.
|
||||
if (Roots.size() > 1)
|
||||
WorkingSet.insert(0);
|
||||
}
|
||||
|
||||
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.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
|
||||
}
|
||||
WorkingSet.clear(); // Clear out the set for next iteration
|
||||
}
|
||||
} while (Changed);
|
||||
return false;
|
||||
}
|
||||
|
||||
// getAnalysisUsage - This obviously provides a post-dominator set, but it also
|
||||
// requires the UnifyFunctionExitNodes pass.
|
||||
//
|
||||
void PostDominatorSet::getAnalysisUsage(AnalysisUsage &AU) const {
|
||||
AU.setPreservesAll();
|
||||
AU.addRequired<UnifyFunctionExitNodes>();
|
||||
}
|
||||
|
||||
//===----------------------------------------------------------------------===//
|
||||
// ImmediatePostDominators Implementation
|
||||
//===----------------------------------------------------------------------===//
|
||||
@ -107,17 +109,25 @@ static RegisterAnalysis<PostDominatorTree>
|
||||
F("postdomtree", "Post-Dominator Tree Construction", true);
|
||||
|
||||
void PostDominatorTree::calculate(const PostDominatorSet &DS) {
|
||||
Nodes[Root] = new Node(Root, 0); // Add a node for the root...
|
||||
if (Roots.empty()) return;
|
||||
BasicBlock *Root = Roots.size() == 1 ? Roots[0] : 0;
|
||||
|
||||
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) {
|
||||
Nodes[Root] = RootNode = new Node(Root, 0); // Add a node for the root...
|
||||
|
||||
// Iterate over all nodes in depth first order...
|
||||
for (unsigned i = 0, e = Roots.size(); i != e; ++i)
|
||||
for (idf_iterator<BasicBlock*> I = idf_begin(Roots[i]),
|
||||
E = idf_end(Roots[i]); I != E; ++I) {
|
||||
BasicBlock *BB = *I;
|
||||
const DominatorSet::DomSetType &Dominators = DS.getDominators(BB);
|
||||
unsigned DomSetSize = Dominators.size();
|
||||
if (DomSetSize == 1) continue; // Root node... IDom = null
|
||||
|
||||
|
||||
// If we have already computed the immediate dominator for this node,
|
||||
// don't revisit. This can happen due to nodes reachable from multiple
|
||||
// roots, but which the idf_iterator doesn't know about.
|
||||
if (Nodes.find(BB) != Nodes.end()) continue;
|
||||
|
||||
// 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
|
||||
@ -130,28 +140,27 @@ void PostDominatorTree::calculate(const PostDominatorSet &DS) {
|
||||
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?");
|
||||
// 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;
|
||||
}
|
||||
// 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;
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
//===----------------------------------------------------------------------===//
|
||||
@ -167,14 +176,14 @@ PostDominanceFrontier::calculate(const PostDominatorTree &DT,
|
||||
// Loop over CFG successors to calculate DFlocal[Node]
|
||||
BasicBlock *BB = Node->getNode();
|
||||
DomSetType &S = Frontiers[BB]; // The new set to fill in...
|
||||
if (!Root) return S;
|
||||
if (getRoots().empty()) return S;
|
||||
|
||||
for (pred_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);
|
||||
}
|
||||
if (BB)
|
||||
for (pred_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
|
||||
|
Loading…
Reference in New Issue
Block a user