#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/Hashing.h"
#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/InstructionSimplify.h"
return false;
}
+static bool
+simplifyAndDCEInstruction(Instruction *I,
+ SmallSetVector<Instruction *, 16> &WorkList,
+ const DataLayout &DL,
+ const TargetLibraryInfo *TLI) {
+ if (isInstructionTriviallyDead(I, TLI)) {
+ // Null out all of the instruction's operands to see if any operand becomes
+ // dead as we go.
+ for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
+ Value *OpV = I->getOperand(i);
+ I->setOperand(i, nullptr);
+
+ if (!OpV->use_empty() || I == OpV)
+ continue;
+
+ // If the operand is an instruction that became dead as we nulled out the
+ // operand, and if it is 'trivially' dead, delete it in a future loop
+ // iteration.
+ if (Instruction *OpI = dyn_cast<Instruction>(OpV))
+ if (isInstructionTriviallyDead(OpI, TLI))
+ WorkList.insert(OpI);
+ }
+
+ I->eraseFromParent();
+
+ return true;
+ }
+
+ if (Value *SimpleV = SimplifyInstruction(I, DL)) {
+ // Add the users to the worklist. CAREFUL: an instruction can use itself,
+ // in the case of a phi node.
+ for (User *U : I->users())
+ if (U != I)
+ WorkList.insert(cast<Instruction>(U));
+
+ // Replace the instruction with its simplified value.
+ I->replaceAllUsesWith(SimpleV);
+ I->eraseFromParent();
+ return true;
+ }
+ return false;
+}
+
/// SimplifyInstructionsInBlock - Scan the specified basic block and try to
/// simplify any instructions in it and recursively delete dead instructions.
///
bool llvm::SimplifyInstructionsInBlock(BasicBlock *BB,
const TargetLibraryInfo *TLI) {
bool MadeChange = false;
+ const DataLayout &DL = BB->getModule()->getDataLayout();
#ifndef NDEBUG
// In debug builds, ensure that the terminator of the block is never replaced
AssertingVH<Instruction> TerminatorVH(--BB->end());
#endif
- for (BasicBlock::iterator BI = BB->begin(), E = --BB->end(); BI != E; ) {
+ SmallSetVector<Instruction *, 16> WorkList;
+ // Iterate over the original function, only adding insts to the worklist
+ // if they actually need to be revisited. This avoids having to pre-init
+ // the worklist with the entire function's worth of instructions.
+ for (BasicBlock::iterator BI = BB->begin(), E = std::prev(BB->end()); BI != E;) {
assert(!BI->isTerminator());
- Instruction *Inst = BI++;
+ Instruction *I = &*BI;
+ ++BI;
- WeakVH BIHandle(BI);
- if (recursivelySimplifyInstruction(Inst, TLI)) {
- MadeChange = true;
- if (BIHandle != BI)
- BI = BB->begin();
- continue;
- }
+ // We're visiting this instruction now, so make sure it's not in the
+ // worklist from an earlier visit.
+ if (!WorkList.count(I))
+ MadeChange |= simplifyAndDCEInstruction(I, WorkList, DL, TLI);
+ }
- MadeChange |= RecursivelyDeleteTriviallyDeadInstructions(Inst, TLI);
- if (BIHandle != BI)
- BI = BB->begin();
+ while (!WorkList.empty()) {
+ Instruction *I = WorkList.pop_back_val();
+ MadeChange |= simplifyAndDCEInstruction(I, WorkList, DL, TLI);
}
return MadeChange;
}