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Factor some code out of SimplifyCFG, forming a new

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DeleteBlockIfDead method.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60463 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2008-12-03 06:37:44 +00:00
parent 62c939d7d5
commit 2b1ba24fb7
3 changed files with 39 additions and 21 deletions
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22
lib/Transforms/Utils/SimplifyCFG.cpp
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@@ -1681,27 +1681,7 @@ bool llvm::SimplifyCFG(BasicBlock *BB) {
// as a predecessor. These are unreachable.
if (pred_begin(BB) == pred_end(BB) || BB->getSinglePredecessor() == BB) {
DOUT << "Removing BB: \n" << *BB;
// Loop through all of our successors and make sure they know that one
// of their predecessors is going away.
for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
SI->removePredecessor(BB);
while (!BB->empty()) {
Instruction &I = BB->back();
// If this instruction is used, replace uses with an arbitrary
// value. Because control flow can't get here, we don't care
// what we replace the value with. Note that since this block is
// unreachable, and all values contained within it must dominate their
// uses, that all uses will eventually be removed.
if (!I.use_empty())
// Make all users of this instruction use undef instead
I.replaceAllUsesWith(UndefValue::get(I.getType()));
// Remove the instruction from the basic block
BB->getInstList().pop_back();
}
BB->eraseFromParent();
DeleteBlockIfDead(BB);
return true;
}