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Fix bug: LoopPreheaders/2003-04-25-AssertFail.ll

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5959 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2003-04-26 19:34:18 +00:00
parent aa709d065a
commit 99224aec78
1 changed files with 24 additions and 3 deletions
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27
lib/Analysis/LoopInfo.cpp
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@ -128,12 +128,12 @@ Loop *LoopInfo::ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS) {
std::vector<BasicBlock *> TodoStack;
// Scan the predecessors of BB, checking to see if BB dominates any of
// them.
// them. This identifies backedges which target this node...
for (pred_iterator I = pred_begin(BB), E = pred_end(BB); I != E; ++I)
if (DS.dominates(BB, *I)) // If BB dominates it's predecessor...
TodoStack.push_back(*I);
if (TodoStack.empty()) return 0; // Doesn't dominate any predecessors...
if (TodoStack.empty()) return 0; // No backedges to this block...
// Create a new loop to represent this basic block...
Loop *L = new Loop(BB);
@ -144,8 +144,29 @@ Loop *LoopInfo::ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS) {
TodoStack.pop_back();
if (!L->contains(X)) { // As of yet unprocessed??
// Check to see if this block already belongs to a loop. If this occurs
// then we have a case where a loop that is supposed to be a child of the
// current loop was processed before the current loop. When this occurs,
// this child loop gets added to a part of the current loop, making it a
// sibling to the current loop. We have to reparent this loop.
if (Loop *SubLoop = const_cast<Loop*>(getLoopFor(X)))
if (SubLoop->getHeader() == X && X != BB) {
// Remove the subloop from it's current parent...
assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L);
Loop *SLP = SubLoop->ParentLoop; // SubLoopParent
std::vector<Loop*>::iterator I =
std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop);
assert(I != SLP->SubLoops.end() && "SubLoop not a child of parent?");
SLP->SubLoops.erase(I); // Remove from parent...
// Add the subloop to THIS loop...
SubLoop->ParentLoop = L;
L->SubLoops.push_back(SubLoop);
}
// Normal case, add the block to our loop...
L->Blocks.push_back(X);
// Add all of the predecessors of X to the end of the work stack...
TodoStack.insert(TodoStack.end(), pred_begin(X), pred_end(X));
}