/// getConstant - Determine whether the specified value is known to be a
/// constant at the end of the specified block. Return null if not.
Constant *getConstant(Value *V, BasicBlock *BB);
+
+ /// getConstantOnEdge - Determine whether the specified value is known to be a
+ /// constant on the specified edge. Return null if not.
+ Constant *getConstantOnEdge(Value *V, BasicBlock *FromBB, BasicBlock *ToBB);
// Implementation boilerplate.
return 0;
}
+/// getConstantOnEdge - Determine whether the specified value is known to be a
+/// constant on the specified edge. Return null if not.
+Constant *LazyValueInfo::getConstantOnEdge(Value *V, BasicBlock *FromBB,
+ BasicBlock *ToBB) {
+ // If already a constant, return it.
+ if (Constant *VC = dyn_cast<Constant>(V))
+ return VC;
+
+ DenseMap<BasicBlock*, LVILatticeVal> BlockValues;
+
+ DEBUG(errs() << "Getting value " << *V << " on edge from '"
+ << FromBB->getName() << "' to '" << ToBB->getName() << "'\n");
+ LVILatticeVal Result = GetValueOnEdge(V, FromBB, ToBB, BlockValues);
+
+ DEBUG(errs() << " Result = " << Result << "\n");
+
+ if (Result.isConstant())
+ return Result.getConstant();
+ return 0;
+}
+
/// isEqual - Determine whether the specified value is known to be equal or
/// not-equal to the specified constant at the end of the specified block.
LazyValueInfo::Tristate
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
// If the value is known by LazyValueInfo to be a constant in a
// predecessor, use that information to try to thread this block.
- Constant *PredCst = LVI->getConstant(V, *PI);
+ Constant *PredCst = LVI->getConstantOnEdge(V, *PI, BB);
if (PredCst == 0 ||
(!isa<ConstantInt>(PredCst) && !isa<UndefValue>(PredCst)))
continue;
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
// If the value is known by LazyValueInfo to be a constant in a
// predecessor, use that information to try to thread this block.
- Constant *PredCst = LVI->getConstant(Cmp->getOperand(0), *PI);
+ Constant *PredCst = LVI->getConstantOnEdge(Cmp->getOperand(0), *PI, BB);
if (PredCst == 0)
continue;