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At Chris' suggestion, move the liveness and worklist datastructures into 

instance variables so they can be allocated just once, and reuse the worklist
as the dead list as well.

llvm-svn: 52618
This commit is contained in:
Owen Anderson 2008-06-23 06:13:12 +00:00
parent 5ca5e02480
commit 00fdbd01e5
1 changed files with 11 additions and 7 deletions
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18
llvm/lib/Transforms/Scalar/ADCE.cpp
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@ -22,6 +22,7 @@
#include "llvm/Support/InstIterator.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
using namespace llvm;
@ -32,6 +33,9 @@ namespace {
static char ID; // Pass identification, replacement for typeid
ADCE() : FunctionPass((intptr_t)&ID) {}
SmallPtrSet<Instruction*, 1024> alive;
SmallVector<Instruction*, 1024> worklist;
virtual bool runOnFunction(Function& F);
virtual void getAnalysisUsage(AnalysisUsage& AU) const {
@ -45,8 +49,8 @@ char ADCE::ID = 0;
static RegisterPass<ADCE> X("adce", "Aggressive Dead Code Elimination");
bool ADCE::runOnFunction(Function& F) {
SmallPtrSet<Instruction*, 32> alive;
std::vector<Instruction*> worklist;
alive.clear();
worklist.clear();
// Collect the set of "root" instructions that are known live.
for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
@ -71,20 +75,20 @@ bool ADCE::runOnFunction(Function& F) {
// The inverse of the live set is the dead set. These are those instructions
// which have no side effects and do not influence the control flow or return
// value of the function, and may therefore be deleted safely.
SmallPtrSet<Instruction*, 32> dead;
// NOTE: We reuse the worklist vector here for memory efficiency.
for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
if (!alive.count(I.getInstructionIterator())) {
dead.insert(I.getInstructionIterator());
worklist.push_back(I.getInstructionIterator());
I->dropAllReferences();
}
for (SmallPtrSet<Instruction*, 32>::iterator I = dead.begin(),
E = dead.end(); I != E; ++I) {
for (SmallVector<Instruction*, 1024>::iterator I = worklist.begin(),
E = worklist.end(); I != E; ++I) {
NumRemoved++;
(*I)->eraseFromParent();
}
return !dead.empty();
return !worklist.empty();
}
FunctionPass *llvm::createAggressiveDCEPass() {