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[LCG] Rather than removing nodes from the SCC entry set when we process

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them, just skip over any DFS-numbered nodes when finding the next root
of a DFS. This allows the entry set to just be a vector as we populate
it from a uniqued source. It also removes the possibility for a linear
scan of the entry set to actually do the removal which can make things
go quadratic if we get unlucky.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207312 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chandler Carruth 2014-04-26 09:45:55 +00:00
parent 797bbced53
commit 9a1fab37c7
2 changed files with 8 additions and 7 deletions
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2
include/llvm/Analysis/LazyCallGraph.h
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@ -384,7 +384,7 @@ private:
SmallVector<std::pair<Node *, iterator>, 4> DFSStack;
/// \brief Set of entry nodes not-yet-processed into SCCs.
SmallSetVector<Function *, 4> SCCEntryNodes;
SmallVector<Function *, 4> SCCEntryNodes;
/// \brief Stack of nodes the DFS has walked but not yet put into a SCC.
SmallVector<Node *, 4> PendingSCCStack;

13
lib/Analysis/LazyCallGraph.cpp
View File

@ -100,9 +100,9 @@ LazyCallGraph::LazyCallGraph(Module &M) : NextDFSNumber(0) {
for (auto &Entry : EntryNodes)
if (Function *F = Entry.dyn_cast<Function *>())
SCCEntryNodes.insert(F);
SCCEntryNodes.push_back(F);
else
SCCEntryNodes.insert(&Entry.get<Node *>()->getFunction());
SCCEntryNodes.push_back(&Entry.get<Node *>()->getFunction());
}
LazyCallGraph::LazyCallGraph(LazyCallGraph &&G)
@ -437,10 +437,12 @@ LazyCallGraph::SCC *LazyCallGraph::getNextSCCInPostOrder() {
DFSStack.pop_back();
} else {
// If we've handled all candidate entry nodes to the SCC forest, we're done.
if (SCCEntryNodes.empty())
return nullptr;
do {
if (SCCEntryNodes.empty())
return nullptr;
N = &get(*SCCEntryNodes.pop_back_val());
N = &get(*SCCEntryNodes.pop_back_val());
} while (N->DFSNumber != 0);
I = N->begin();
N->LowLink = N->DFSNumber = 1;
NextDFSNumber = 2;
@ -463,7 +465,6 @@ LazyCallGraph::SCC *LazyCallGraph::getNextSCCInPostOrder() {
assert(!SCCMap.count(&ChildN) &&
"Found a node with 0 DFS number but already in an SCC!");
ChildN.LowLink = ChildN.DFSNumber = NextDFSNumber++;
SCCEntryNodes.remove(&ChildN.getFunction());
N = &ChildN;
I = ChildN.begin();
E = ChildN.end();