[llvm-commits] [llvm] r123273 - in /llvm/trunk/include/llvm/Analysis: DominatorInternals.h Dominators.h
Jakob Stoklund Olesen
stoklund at 2pi.dk
Tue Jan 11 13:23:09 PST 2011
Author: stoklund
Date: Tue Jan 11 15:23:09 2011
New Revision: 123273
URL: http://llvm.org/viewvc/llvm-project?rev=123273&view=rev
Log:
Put the Dominator improvements back in. They were not the cause of bootstrap miscomparisons.
Modified:
llvm/trunk/include/llvm/Analysis/DominatorInternals.h
llvm/trunk/include/llvm/Analysis/Dominators.h
Modified: llvm/trunk/include/llvm/Analysis/DominatorInternals.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/DominatorInternals.h?rev=123273&r1=123272&r2=123273&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Analysis/DominatorInternals.h (original)
+++ llvm/trunk/include/llvm/Analysis/DominatorInternals.h Tue Jan 11 15:23:09 2011
@@ -22,13 +22,9 @@
// A Fast Algorithm for Finding Dominators in a Flowgraph
// T. Lengauer & R. Tarjan, ACM TOPLAS July 1979, pgs 121-141.
//
-// This implements both the O(n*ack(n)) and the O(n*log(n)) versions of EVAL and
-// LINK, but it turns out that the theoretically slower O(n*log(n))
-// implementation is actually faster than the "efficient" algorithm (even for
-// large CFGs) because the constant overheads are substantially smaller. The
-// lower-complexity version can be enabled with the following #define:
-//
-#define BALANCE_IDOM_TREE 0
+// This implements the O(n*log(n)) versions of EVAL and LINK, because it turns
+// out that the theoretically slower O(n*log(n)) implementation is actually
+// faster than the almost-linear O(n*alpha(n)) version, even for large CFGs.
//
//===----------------------------------------------------------------------===//
@@ -58,7 +54,7 @@
}
}
#else
- bool IsChilOfArtificialExit = (N != 0);
+ bool IsChildOfArtificialExit = (N != 0);
std::vector<std::pair<typename GraphT::NodeType*,
typename GraphT::ChildIteratorType> > Worklist;
@@ -80,10 +76,10 @@
//BBInfo[V].Child = 0; // Child[v] = 0
BBInfo.Size = 1; // Size[v] = 1
- if (IsChilOfArtificialExit)
+ if (IsChildOfArtificialExit)
BBInfo.Parent = 1;
- IsChilOfArtificialExit = false;
+ IsChildOfArtificialExit = false;
}
// store the DFS number of the current BB - the reference to BBInfo might
@@ -157,75 +153,17 @@
typename GraphT::NodeType *V) {
typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &VInfo =
DT.Info[V];
-#if !BALANCE_IDOM_TREE
- // Higher-complexity but faster implementation
if (VInfo.Ancestor == 0)
return V;
Compress<GraphT>(DT, V);
return VInfo.Label;
-#else
- // Lower-complexity but slower implementation
- if (VInfo.Ancestor == 0)
- return VInfo.Label;
- Compress<GraphT>(DT, V);
- GraphT::NodeType* VLabel = VInfo.Label;
-
- GraphT::NodeType* VAncestorLabel = DT.Info[VInfo.Ancestor].Label;
- if (DT.Info[VAncestorLabel].Semi >= DT.Info[VLabel].Semi)
- return VLabel;
- else
- return VAncestorLabel;
-#endif
}
template<class GraphT>
void Link(DominatorTreeBase<typename GraphT::NodeType>& DT,
unsigned DFSNumV, typename GraphT::NodeType* W,
typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &WInfo) {
-#if !BALANCE_IDOM_TREE
- // Higher-complexity but faster implementation
WInfo.Ancestor = DFSNumV;
-#else
- // Lower-complexity but slower implementation
- GraphT::NodeType* WLabel = WInfo.Label;
- unsigned WLabelSemi = DT.Info[WLabel].Semi;
- GraphT::NodeType* S = W;
- InfoRec *SInfo = &DT.Info[S];
-
- GraphT::NodeType* SChild = SInfo->Child;
- InfoRec *SChildInfo = &DT.Info[SChild];
-
- while (WLabelSemi < DT.Info[SChildInfo->Label].Semi) {
- GraphT::NodeType* SChildChild = SChildInfo->Child;
- if (SInfo->Size+DT.Info[SChildChild].Size >= 2*SChildInfo->Size) {
- SChildInfo->Ancestor = S;
- SInfo->Child = SChild = SChildChild;
- SChildInfo = &DT.Info[SChild];
- } else {
- SChildInfo->Size = SInfo->Size;
- S = SInfo->Ancestor = SChild;
- SInfo = SChildInfo;
- SChild = SChildChild;
- SChildInfo = &DT.Info[SChild];
- }
- }
-
- DominatorTreeBase::InfoRec &VInfo = DT.Info[V];
- SInfo->Label = WLabel;
-
- assert(V != W && "The optimization here will not work in this case!");
- unsigned WSize = WInfo.Size;
- unsigned VSize = (VInfo.Size += WSize);
-
- if (VSize < 2*WSize)
- std::swap(S, VInfo.Child);
-
- while (S) {
- SInfo = &DT.Info[S];
- SInfo->Ancestor = V;
- S = SInfo->Child;
- }
-#endif
}
template<class FuncT, class NodeT>
@@ -257,12 +195,34 @@
// infinite loops). In these cases an artificial exit node is required.
MultipleRoots |= (DT.isPostDominator() && N != F.size());
+ // When naively implemented, the Lengauer-Tarjan algorithm requires a separate
+ // bucket for each vertex. However, this is unnecessary, because each vertex
+ // is only placed into a single bucket (that of its semidominator), and each
+ // vertex's bucket is processed before it is added to any bucket itself.
+ //
+ // Instead of using a bucket per vertex, we use a single array Buckets that
+ // has two purposes. Before the vertex V with preorder number i is processed,
+ // Buckets[i] stores the index of the first element in V's bucket. After V's
+ // bucket is processed, Buckets[i] stores the index of the next element in the
+ // bucket containing V, if any.
+ std::vector<unsigned> Buckets;
+ Buckets.resize(N + 1);
+ for (unsigned i = 1; i <= N; ++i)
+ Buckets[i] = i;
+
for (unsigned i = N; i >= 2; --i) {
typename GraphT::NodeType* W = DT.Vertex[i];
typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &WInfo =
DT.Info[W];
- // Step #2: Calculate the semidominators of all vertices
+ // Step #2: Implicitly define the immediate dominator of vertices
+ for (unsigned j = i; Buckets[j] != i; j = Buckets[j]) {
+ typename GraphT::NodeType* V = DT.Vertex[Buckets[j]];
+ typename GraphT::NodeType* U = Eval<GraphT>(DT, V);
+ DT.IDoms[V] = DT.Info[U].Semi < i ? U : W;
+ }
+
+ // Step #3: Calculate the semidominators of all vertices
// initialize the semi dominator to point to the parent node
WInfo.Semi = WInfo.Parent;
@@ -278,26 +238,24 @@
}
}
- typename GraphT::NodeType* WParent = DT.Vertex[WInfo.Parent];
-
// If V is a non-root vertex and sdom(V) = parent(V), then idom(V) is
// necessarily parent(V). In this case, set idom(V) here and avoid placing
// V into a bucket.
- if (WInfo.Semi == WInfo.Parent)
- DT.IDoms[W] = WParent;
- else
- DT.Info[DT.Vertex[WInfo.Semi]].Bucket.push_back(W);
+ if (WInfo.Semi == WInfo.Parent) {
+ DT.IDoms[W] = DT.Vertex[WInfo.Parent];
+ } else {
+ Buckets[i] = Buckets[WInfo.Semi];
+ Buckets[WInfo.Semi] = i;
+ }
Link<GraphT>(DT, WInfo.Parent, W, WInfo);
+ }
- // Step #3: Implicitly define the immediate dominator of vertices
- std::vector<typename GraphT::NodeType*> &WParentBucket =
- DT.Info[WParent].Bucket;
- while (!WParentBucket.empty()) {
- typename GraphT::NodeType* V = WParentBucket.back();
- WParentBucket.pop_back();
- typename GraphT::NodeType* U = Eval<GraphT>(DT, V);
- DT.IDoms[V] = DT.Info[U].Semi < DT.Info[V].Semi ? U : WParent;
+ if (N >= 1) {
+ typename GraphT::NodeType* Root = DT.Vertex[1];
+ for (unsigned j = 1; Buckets[j] != 1; j = Buckets[j]) {
+ typename GraphT::NodeType* V = DT.Vertex[Buckets[j]];
+ DT.IDoms[V] = Root;
}
}
Modified: llvm/trunk/include/llvm/Analysis/Dominators.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/Dominators.h?rev=123273&r1=123272&r2=123273&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Analysis/Dominators.h (original)
+++ llvm/trunk/include/llvm/Analysis/Dominators.h Tue Jan 11 15:23:09 2011
@@ -200,8 +200,6 @@
NodeT *Label, *Child;
unsigned Parent, Ancestor;
- std::vector<NodeT*> Bucket;
-
InfoRec() : DFSNum(0), Semi(0), Size(0), Label(0), Child(0), Parent(0),
Ancestor(0) {}
};
@@ -293,9 +291,6 @@
: DominatorBase<NodeT>(isPostDom), DFSInfoValid(false), SlowQueries(0) {}
virtual ~DominatorTreeBase() { reset(); }
- // FIXME: Should remove this
- virtual bool runOnFunction(Function &F) { return false; }
-
/// compare - Return false if the other dominator tree base matches this
/// dominator tree base. Otherwise return true.
bool compare(DominatorTreeBase &Other) const {
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