[llvm-commits] [llvm] r160366 - in /llvm/trunk/include/llvm: ADT/PostOrderIterator.h Analysis/LoopIterator.h
Jakob Stoklund Olesen
stoklund at 2pi.dk
Tue Jul 17 08:35:40 PDT 2012
Author: stoklund
Date: Tue Jul 17 10:35:40 2012
New Revision: 160366
URL: http://llvm.org/viewvc/llvm-project?rev=160366&view=rev
Log:
Allow for customized graph edge pruning in PostOrderIterator.h
Make it possible to prune individual graph edges from a post-order
traversal by specializing the po_iterator_storage template. Previously,
it was only possible to prune full graph nodes. Edge pruning makes it
possible to remove loop back-edges, for example.
Also replace the existing DFSetTraits customization hook with a
po_iterator_storage method for observing the post-order. DFSetTraits was
only used by LoopIterator.h which now provides a po_iterator_storage
specialization.
Thanks to Sean and Chandler for reviewing.
Modified:
llvm/trunk/include/llvm/ADT/PostOrderIterator.h
llvm/trunk/include/llvm/Analysis/LoopIterator.h
Modified: llvm/trunk/include/llvm/ADT/PostOrderIterator.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/PostOrderIterator.h?rev=160366&r1=160365&r2=160366&view=diff
==============================================================================
--- llvm/trunk/include/llvm/ADT/PostOrderIterator.h (original)
+++ llvm/trunk/include/llvm/ADT/PostOrderIterator.h Tue Jul 17 10:35:40 2012
@@ -23,26 +23,65 @@
namespace llvm {
-template<class SetType, bool External> // Non-external set
+// The po_iterator_storage template provides access to the set of already
+// visited nodes during the po_iterator's depth-first traversal.
+//
+// The default implementation simply contains a set of visited nodes, while
+// the Extended=true version uses a reference to an external set.
+//
+// It is possible to prune the depth-first traversal in several ways:
+//
+// - When providing an external set that already contains some graph nodes,
+// those nodes won't be visited again. This is useful for restarting a
+// post-order traversal on a graph with nodes that aren't dominated by a
+// single node.
+//
+// - By providing a custom SetType class, unwanted graph nodes can be excluded
+// by having the insert() function return false. This could for example
+// confine a CFG traversal to blocks in a specific loop.
+//
+// - Finally, by specializing the po_iterator_storage template itself, graph
+// edges can be pruned by returning false in the insertEdge() function. This
+// could be used to remove loop back-edges from the CFG seen by po_iterator.
+//
+// A specialized po_iterator_storage class can observe both the pre-order and
+// the post-order. The insertEdge() function is called in a pre-order, while
+// the finishPostorder() function is called just before the po_iterator moves
+// on to the next node.
+
+/// Default po_iterator_storage implementation with an internal set object.
+template<class SetType, bool External>
class po_iterator_storage {
-public:
SetType Visited;
-};
+public:
+ // Return true if edge destination should be visited.
+ template<typename NodeType>
+ bool insertEdge(NodeType *From, NodeType *To) {
+ return Visited.insert(To);
+ }
-/// DFSetTraits - Allow the SetType used to record depth-first search results to
-/// optionally record node postorder.
-template<class SetType>
-struct DFSetTraits {
- static void finishPostorder(
- typename SetType::iterator::value_type, SetType &) {}
+ // Called after all children of BB have been visited.
+ template<typename NodeType>
+ void finishPostorder(NodeType *BB) {}
};
+/// Specialization of po_iterator_storage that references an external set.
template<class SetType>
class po_iterator_storage<SetType, true> {
+ SetType &Visited;
public:
po_iterator_storage(SetType &VSet) : Visited(VSet) {}
po_iterator_storage(const po_iterator_storage &S) : Visited(S.Visited) {}
- SetType &Visited;
+
+ // Return true if edge destination should be visited, called with From = 0 for
+ // the root node.
+ // Graph edges can be pruned by specializing this function.
+ template<class NodeType>
+ bool insertEdge(NodeType *From, NodeType *To) { return Visited.insert(To); }
+
+ // Called after all children of BB have been visited.
+ template<class NodeType>
+ void finishPostorder(NodeType *BB) {}
};
template<class GraphT,
@@ -64,14 +103,15 @@
void traverseChild() {
while (VisitStack.back().second != GT::child_end(VisitStack.back().first)) {
NodeType *BB = *VisitStack.back().second++;
- if (this->Visited.insert(BB)) { // If the block is not visited...
+ if (this->insertEdge(VisitStack.back().first, BB)) {
+ // If the block is not visited...
VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
}
}
}
inline po_iterator(NodeType *BB) {
- this->Visited.insert(BB);
+ this->insertEdge((NodeType*)0, BB);
VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
traverseChild();
}
@@ -79,7 +119,7 @@
inline po_iterator(NodeType *BB, SetType &S) :
po_iterator_storage<SetType, ExtStorage>(S) {
- if (this->Visited.insert(BB)) {
+ if (this->insertEdge((NodeType*)0, BB)) {
VisitStack.push_back(std::make_pair(BB, GT::child_begin(BB)));
traverseChild();
}
@@ -117,8 +157,7 @@
inline NodeType *operator->() const { return operator*(); }
inline _Self& operator++() { // Preincrement
- DFSetTraits<SetType>::finishPostorder(VisitStack.back().first,
- this->Visited);
+ this->finishPostorder(VisitStack.back().first);
VisitStack.pop_back();
if (!VisitStack.empty())
traverseChild();
Modified: llvm/trunk/include/llvm/Analysis/LoopIterator.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/LoopIterator.h?rev=160366&r1=160365&r2=160366&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Analysis/LoopIterator.h (original)
+++ llvm/trunk/include/llvm/Analysis/LoopIterator.h Tue Jul 17 10:35:40 2012
@@ -109,6 +109,16 @@
}
};
+/// Specialize po_iterator_storage to record postorder numbers.
+template<> class po_iterator_storage<LoopBlocksTraversal, true> {
+ LoopBlocksTraversal &LBT;
+public:
+ po_iterator_storage(LoopBlocksTraversal &lbs) : LBT(lbs) {}
+ // These functions are defined below.
+ bool insertEdge(BasicBlock *From, BasicBlock *To);
+ void finishPostorder(BasicBlock *BB);
+};
+
/// Traverse the blocks in a loop using a depth-first search.
class LoopBlocksTraversal {
public:
@@ -155,31 +165,17 @@
DFS.PostBlocks.push_back(BB);
DFS.PostNumbers[BB] = DFS.PostBlocks.size();
}
-
- //===----------------------------------------------------------------------
- // Implement part of the std::set interface for the purpose of driving the
- // generic po_iterator.
-
- /// Return true if the block is outside the loop or has already been visited.
- /// Sorry if this is counterintuitive.
- bool count(BasicBlock *BB) const {
- return !DFS.L->contains(LI->getLoopFor(BB)) || DFS.PostNumbers.count(BB);
- }
-
- /// If this block is contained in the loop and has not been visited, return
- /// true and assign a preorder number. This is a proxy for visitPreorder
- /// called by POIterator.
- bool insert(BasicBlock *BB) {
- return visitPreorder(BB);
- }
};
-/// Specialize DFSetTraits to record postorder numbers.
-template<> struct DFSetTraits<LoopBlocksTraversal> {
- static void finishPostorder(BasicBlock *BB, LoopBlocksTraversal& LBT) {
- LBT.finishPostorder(BB);
- }
-};
+inline bool po_iterator_storage<LoopBlocksTraversal, true>::
+insertEdge(BasicBlock *From, BasicBlock *To) {
+ return LBT.visitPreorder(To);
+}
+
+inline void po_iterator_storage<LoopBlocksTraversal, true>::
+finishPostorder(BasicBlock *BB) {
+ LBT.finishPostorder(BB);
+}
} // End namespace llvm
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