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Implement SCCP/ipsccp-conditional.ll, by totally deleting dead blocks.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@18781 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-12-10 22:29:08 +00:00
parent 9b07c66501
commit 5f9e8b4c3f
1 changed files with 29 additions and 2 deletions
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31
lib/Transforms/Scalar/SCCP.cpp
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@ -1109,17 +1109,20 @@ bool IPSCCP::runOnModule(Module &M) {
}
}
std::vector<BasicBlock*> BlocksToErase;
for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
if (!ExecutableBBs.count(BB)) {
DEBUG(std::cerr << " BasicBlock Dead:" << *BB);
++IPNumDeadBlocks;
BlocksToErase.push_back(BB);
// Delete the instructions backwards, as it has a reduced likelihood of
// having to update as many def-use and use-def chains.
std::vector<Instruction*> Insts;
for (BasicBlock::iterator I = BB->begin(), E = BB->getTerminator();
I != E; ++I)
TerminatorInst *TI = BB->getTerminator();
for (BasicBlock::iterator I = BB->begin(), E = TI; I != E; ++I)
Insts.push_back(I);
while (!Insts.empty()) {
Instruction *I = Insts.back();
Insts.pop_back();
@ -1129,6 +1132,14 @@ bool IPSCCP::runOnModule(Module &M) {
MadeChanges = true;
++IPNumInstRemoved;
}
for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) {
BasicBlock *Succ = TI->getSuccessor(i);
if (Succ->begin() != Succ->end() && isa<PHINode>(Succ->begin()))
TI->getSuccessor(i)->removePredecessor(BB);
}
BB->getInstList().erase(TI);
} else {
for (BasicBlock::iterator BI = BB->begin(), E = BB->end(); BI != E; ) {
Instruction *Inst = BI++;
@ -1155,6 +1166,22 @@ bool IPSCCP::runOnModule(Module &M) {
}
}
}
// Now that all instructions in the function are constant folded, erase dead
// blocks, because we can now use ConstantFoldTerminator to get rid of
// in-edges.
for (unsigned i = 0, e = BlocksToErase.size(); i != e; ++i) {
// If there are any PHI nodes in this successor, drop entries for BB now.
BasicBlock *DeadBB = BlocksToErase[i];
while (!DeadBB->use_empty()) {
Instruction *I = cast<Instruction>(DeadBB->use_back());
bool Folded = ConstantFoldTerminator(I->getParent());
assert(Folded && "Didn't fold away reference to block!");
}
// Finally, delete the basic block.
F->getBasicBlockList().erase(DeadBB);
}
}
return MadeChanges;
}