bool CallAnalyzer::visitSwitchInst(SwitchInst &SI) {
// We model unconditional switches as free, see the comments on handling
// branches.
if (isa<ConstantInt>(SI.getCondition()))
return true;
if (Value *V = SimplifiedValues.lookup(SI.getCondition()))
if (isa<ConstantInt>(V))
return true;
// Otherwise, we need to accumulate a cost proportional to the number of
// distinct successor blocks. This fan-out in the CFG cannot be represented
// for free even if we can represent the core switch as a jumptable that
// takes a single instruction.
//
// NB: We convert large switches which are just used to initialize large phi
// nodes to lookup tables instead in simplify-cfg, so this shouldn't prevent
// inlining those. It will prevent inlining in cases where the optimization
// does not (yet) fire.
SmallPtrSet<BasicBlock *, 8> SuccessorBlocks;
SuccessorBlocks.insert(SI.getDefaultDest());
for (auto I = SI.case_begin(), E = SI.case_end(); I != E; ++I)
SuccessorBlocks.insert(I.getCaseSuccessor());
// Add cost corresponding to the number of distinct destinations. The first
// we model as free because of fallthrough.
Cost += (SuccessorBlocks.size() - 1) * InlineConstants::InstrCost;
return false;
}
void Interpreter::visitSwitchInst(SwitchInst &I) {
ExecutionContext &SF = ECStack.back();
GenericValue CondVal = getOperandValue(I.getOperand(0), SF);
const Type *ElTy = I.getOperand(0)->getType();
// Check to see if any of the cases match...
BasicBlock *Dest = 0;
for (unsigned i = 2, e = I.getNumOperands(); i != e; i += 2)
if (executeSetEQInst(CondVal,
getOperandValue(I.getOperand(i), SF), ElTy).BoolVal) {
Dest = cast<BasicBlock>(I.getOperand(i+1));
break;
}
if (!Dest) Dest = I.getDefaultDest(); // No cases matched: use default
SwitchToNewBasicBlock(Dest, SF);
}