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Put the Dominator improvements back in. They were not the cause of bootstrap miscomparisons.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123273 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2011-01-11 21:23:09 +00:00
parent e641863cd2
commit 113328db1b
2 changed files with 41 additions and 88 deletions
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124
include/llvm/Analysis/DominatorInternals.h
View File

@ -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 @@ unsigned DFSPass(DominatorTreeBase<typename GraphT::NodeType>& DT,
}
}
#else
bool IsChilOfArtificialExit = (N != 0);
bool IsChildOfArtificialExit = (N != 0);
std::vector<std::pair<typename GraphT::NodeType*,
typename GraphT::ChildIteratorType> > Worklist;
@ -80,10 +76,10 @@ unsigned DFSPass(DominatorTreeBase<typename GraphT::NodeType>& DT,
//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 @@ Eval(DominatorTreeBase<typename GraphT::NodeType>& DT,
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 @@ void Calculate(DominatorTreeBase<typename GraphTraits<NodeT>::NodeType>& DT,
// 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 @@ void Calculate(DominatorTreeBase<typename GraphTraits<NodeT>::NodeType>& DT,
}
}
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;
}
}

5
include/llvm/Analysis/Dominators.h
View File

@ -200,8 +200,6 @@ protected:
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 @@ public:
: 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 {