-//===-- GCSE.cpp - SSA based Global Common Subexpr Elimination ------------===//
+//===-- GCSE.cpp - SSA-based Global Common Subexpression Elimination ------===//
//
// The LLVM Compiler Infrastructure
//
Statistic<> NumCallRemoved("gcse", "Number of calls removed");
Statistic<> NumNonInsts ("gcse", "Number of instructions removed due "
"to non-instruction values");
+ Statistic<> NumArgsRepl ("gcse", "Number of function arguments replaced "
+ "with constant values");
struct GCSE : public FunctionPass {
virtual bool runOnFunction(Function &F);
std::vector<Value*> EqualValues;
+ // Check for value numbers of arguments. If the value numbering
+ // implementation can prove that an incoming argument is a constant or global
+ // value address, substitute it, making the argument dead.
+ for (Function::aiterator AI = F.abegin(), E = F.aend(); AI != E; ++AI)
+ if (!AI->use_empty()) {
+ VN.getEqualNumberNodes(AI, EqualValues);
+ if (!EqualValues.empty()) {
+ for (unsigned i = 0, e = EqualValues.size(); i != e; ++i)
+ if (isa<Constant>(EqualValues[i]) ||
+ isa<GlobalValue>(EqualValues[i])) {
+ AI->replaceAllUsesWith(EqualValues[i]);
+ ++NumArgsRepl;
+ Changed = true;
+ break;
+ }
+ EqualValues.clear();
+ }
+ }
+
// Traverse the CFG of the function in dominator order, so that we see each
// instruction after we see its operands.
for (df_iterator<DominatorTree::Node*> DI = df_begin(DT.getRootNode()),
++NumInstRemoved; // Keep track of number of insts eliminated
// Update value numbering
- getAnalysis<ValueNumbering>().deleteInstruction(I);
+ getAnalysis<ValueNumbering>().deleteValue(I);
// If we are not replacing the instruction with a constant, we cannot do
// anything special.