// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
bool Peephole::DoOneIteration(Function* function) {
bool changed = false;
int position = 0;
while(position < worklist_.Count()) {
// Get the instruction at the current position and try to simplify it.
Instruction* instr = worklist_[position++];
// Branching instructions don't have any resulting operand,
// and report a simplification by returning 'true'.
if(instr->IsBranching()) {
changed |= ProcessBranching(instr);
continue;
}
// For all other kinds of instructions.
// If the result is 'nullptr' nothing could be simplified.
auto result = Simplify(instr);
if(result == nullptr) continue;
if(result->IsUndefinedConstant()) {
if(HandleUndefinedResult(instr)) {
// The instruction should not be considered below.
continue;
}
}
// Replace the previous result operand with the new one
// in all instructions that use it as a source operand.
instr->GetDestinationOp()->ReplaceWith(result);
InstructionSimplified(instr, result);
HandleSpecialCases(instr, result);
changed = true;
#if 1
IRPrinter(function).Dump();
#endif
}
// Some instructions may be dead now; delete them here, so that
// the next iteration doesn't consider them anymore. Note that
// this is necessary, else we would enter an infinite loop simplifying
// the same instructions again and again...
if(changed) DeleteDeadInstructions(function);
return changed;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
void AggregateCopyPropagation::ReplaceWithOriginal(LoadInstr* instr,
TOperandToIdDict& availableCopies,
BitVector& killSet) {
if(availableCopies.Count() == 0) {
return;
}
// Try to replace each operand with the original one
// (the one from which the copy was made).
Instruction* lastInstr = nullptr;
auto candidateOp = GetBaseOperand(instr->SourceOp(), &lastInstr);
// Give up if we couldn't find a candidate,
// or if the candidate is an instruction whose result
// is used in more than one place.
if((candidateOp == nullptr) || (lastInstr == nullptr) ||
(lastInstr->GetDestinationOp()->HasSingleUser() == false)) {
return;
}
// We can replace the operand if it's a copy
// (found in 'availableCopies') and the source or copy
// was not killed until this point.
CopySetInfo info;
if(GetOldestAvailable(candidateOp, availableCopies, killSet, info)) {
if(info.IsCopy) {
// Replace the operand with the original.
auto originalOp = info.Source;
lastInstr->ReplaceSourceOp(0, originalOp);
info.Replacements++;
CopyPropagated(instr);
}
else if(instr->HasDestinationOp()) {
// The load itself is replaced by the value
// to which the record/array was set.
auto requiredType = instr->GetDestinationOp()->GetType();
auto constantOp = CreateConstant(requiredType, info);
instr->GetDestinationOp()->ReplaceWith(constantOp);
info.Replacements++;
CopyPropagated(instr);
}
}
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
void AggregateCopyPropagation::ReplaceWithOriginal(CallInstr* instr,
TOperandToIdDict& availableCopies,
BitVector& killSet) {
// Check if any of the arguments can be replaced
// with the original operand.
for(int i = 0; i < instr->ArgumentCount(); i++) {
auto argument = instr->GetArgument(i);
Instruction* lastInstr = nullptr;
auto candidateOp = GetBaseOperand(argument, &lastInstr);
// Give up if we couldn't find a candidate,
// or if the candidate is used by an instruction
// whose result is used in more than one place.
if((candidateOp == nullptr) ||
(lastInstr && (lastInstr->GetDestinationOp()->HasSingleUser() == false))) {
return;
}
// Check if this is a copy.
CopySetInfo info;
if(GetOldestAvailable(candidateOp, availableCopies, killSet, info)) {
if(info.IsCopy) {
// Replace the operand with the original.
auto originalOp = info.Source;
info.Replacements++;
CopyPropagated(instr);
// If the copy is used by an instruction, we modify
// that instruction, else we replace the call argument.
if(lastInstr) {
lastInstr->ReplaceSourceOp(0, originalOp);
}
else instr->ReplaceArgument(i, originalOp);
}
}
}
}