//
// This file implements the Aggressive Dead Code Elimination pass. This pass
// optimistically assumes that all instructions are dead until proven otherwise,
-// allowing it to eliminate dead computations that other DCE passes do not
+// allowing it to eliminate dead computations that other DCE passes do not
// catch, particularly involving loop computations.
//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "adce"
#include "llvm/Transforms/Scalar.h"
-#include "llvm/BasicBlock.h"
-#include "llvm/Instructions.h"
-#include "llvm/Pass.h"
-#include "llvm/Support/CFG.h"
-#include "llvm/Support/Compiler.h"
-#include "llvm/Support/InstIterator.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
-
+#include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/CFG.h"
+#include "llvm/IR/InstIterator.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/Pass.h"
using namespace llvm;
+#define DEBUG_TYPE "adce"
+
STATISTIC(NumRemoved, "Number of instructions removed");
namespace {
- struct VISIBILITY_HIDDEN ADCE : public FunctionPass {
+ struct ADCE : public FunctionPass {
static char ID; // Pass identification, replacement for typeid
- ADCE() : FunctionPass(&ID) {}
-
- virtual bool runOnFunction(Function& F);
-
- virtual void getAnalysisUsage(AnalysisUsage& AU) const {
+ ADCE() : FunctionPass(ID) {
+ initializeADCEPass(*PassRegistry::getPassRegistry());
+ }
+
+ bool runOnFunction(Function& F) override;
+
+ void getAnalysisUsage(AnalysisUsage& AU) const override {
AU.setPreservesCFG();
}
-
+
};
}
char ADCE::ID = 0;
-static RegisterPass<ADCE> X("adce", "Aggressive Dead Code Elimination");
+INITIALIZE_PASS(ADCE, "adce", "Aggressive Dead Code Elimination", false, false)
bool ADCE::runOnFunction(Function& F) {
+ if (skipOptnoneFunction(F))
+ return false;
+
SmallPtrSet<Instruction*, 128> alive;
SmallVector<Instruction*, 128> worklist;
-
+
// Collect the set of "root" instructions that are known live.
for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
if (isa<TerminatorInst>(I.getInstructionIterator()) ||
- I->mayWriteToMemory()) {
+ isa<DbgInfoIntrinsic>(I.getInstructionIterator()) ||
+ isa<LandingPadInst>(I.getInstructionIterator()) ||
+ I->mayHaveSideEffects()) {
alive.insert(I.getInstructionIterator());
worklist.push_back(I.getInstructionIterator());
}
-
+
// Propagate liveness backwards to operands.
while (!worklist.empty()) {
- Instruction* curr = worklist.back();
- worklist.pop_back();
-
+ Instruction* curr = worklist.pop_back_val();
for (Instruction::op_iterator OI = curr->op_begin(), OE = curr->op_end();
OI != OE; ++OI)
if (Instruction* Inst = dyn_cast<Instruction>(OI))
if (alive.insert(Inst))
worklist.push_back(Inst);
}
-
+
// 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.
worklist.push_back(I.getInstructionIterator());
I->dropAllReferences();
}
-
- for (SmallVector<Instruction*, 1024>::iterator I = worklist.begin(),
+
+ for (SmallVectorImpl<Instruction *>::iterator I = worklist.begin(),
E = worklist.end(); I != E; ++I) {
- NumRemoved++;
+ ++NumRemoved;
(*I)->eraseFromParent();
}