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clean up and modernize this pass.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21776 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-05-08 18:45:26 +00:00
parent 120347e8d1
commit 928128281f
1 changed files with 18 additions and 24 deletions
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42
lib/Transforms/Scalar/DCE.cpp
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@ -77,20 +77,19 @@ namespace {
bool DCE::runOnFunction(Function &F) {
// Start out with all of the instructions in the worklist...
std::vector<Instruction*> WorkList;
for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i) {
WorkList.push_back(&*i);
}
std::set<Instruction*> DeadInsts;
for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)
WorkList.push_back(&*i);
// Loop over the worklist finding instructions that are dead. If they are
// dead make them drop all of their uses, making other instructions
// potentially dead, and work until the worklist is empty.
//
bool MadeChange = false;
while (!WorkList.empty()) {
Instruction *I = WorkList.back();
WorkList.pop_back();
if (isInstructionTriviallyDead(I)) { // If the instruction is dead...
if (isInstructionTriviallyDead(I)) { // If the instruction is dead.
// Loop over all of the values that the instruction uses, if there are
// instructions being used, add them to the worklist, because they might
// go dead after this one is removed.
@ -99,28 +98,23 @@ bool DCE::runOnFunction(Function &F) {
if (Instruction *Used = dyn_cast<Instruction>(*OI))
WorkList.push_back(Used);
// Tell the instruction to let go of all of the values it uses...
I->dropAllReferences();
// Remove the instruction.
I->eraseFromParent();
// Keep track of this instruction, because we are going to delete it later
DeadInsts.insert(I);
// Remove the instruction from the worklist if it still exists in it.
for (std::vector<Instruction*>::iterator WI = WorkList.begin(),
E = WorkList.end(); WI != E; ++WI)
if (*WI == I) {
WorkList.erase(WI);
--E;
--WI;
}
MadeChange = true;
++DCEEliminated;
}
}
// If we found no dead instructions, we haven't changed the function...
if (DeadInsts.empty()) return false;
// Otherwise, loop over the program, removing and deleting the instructions...
for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
for (BasicBlock::iterator BI = I->begin(); BI != I->end(); )
if (DeadInsts.count(BI)) { // Is this instruction dead?
BI = I->getInstList().erase(BI); // Yup, remove and delete inst
++DCEEliminated;
} else { // This instruction is not dead
++BI; // Continue on to the next one...
}
return true;
return MadeChange;
}
FunctionPass *llvm::createDeadCodeEliminationPass() {