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Fix bug: SimplifyCFG/2003-03-07-DominateProblem.ll

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5722 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2003-03-07 18:13:41 +00:00
parent 5db057fbb0
commit 3a43837d85
1 changed files with 19 additions and 2 deletions
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21
lib/Transforms/Utils/SimplifyCFG.cpp
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@ -141,9 +141,11 @@ bool SimplifyCFG(BasicBlock *BB) {
//
if (!PropagatePredecessorsForPHIs(BB, Succ)) {
//cerr << "Killing Trivial BB: \n" << BB;
BB->replaceAllUsesWith(Succ);
std::string OldName = BB->getName();
std::vector<BasicBlock*>
OldSuccPreds(pred_begin(Succ), pred_end(Succ));
// Move all PHI nodes in BB to Succ if they are alive, otherwise
// delete them.
while (PHINode *PN = dyn_cast<PHINode>(&BB->front()))
@ -152,11 +154,26 @@ bool SimplifyCFG(BasicBlock *BB) {
else {
// The instruction is alive, so this means that Succ must have
// *ONLY* had BB as a predecessor, and the PHI node is still valid
// now. Simply move it into Succ.
// now. Simply move it into Succ, because we know that BB
// strictly dominated Succ.
BB->getInstList().remove(BB->begin());
Succ->getInstList().push_front(PN);
// We need to add new entries for the PHI node to account for
// predecessors of Succ that the PHI node does not take into
// account. At this point, since we know that BB dominated succ,
// this means that we should any newly added incoming edges should
// use the PHI node as the value for these edges, because they are
// loop back edges.
for (unsigned i = 0, e = OldSuccPreds.size(); i != e; ++i)
if (OldSuccPreds[i] != BB)
PN->addIncoming(PN, OldSuccPreds[i]);
}
// Everything that jumped to BB now goes to Succ...
BB->replaceAllUsesWith(Succ);
// Delete the old basic block...
M->getBasicBlockList().erase(BB);