//
// This can help use eliminate writes to %block that are not used since this is
// a special local-variable, not programmer-defined local-variable
public void computeScopeFlags() {
if (flagsComputed) {
return;
}
// init
canModifyCode = true;
canCaptureCallersBinding = false;
usesZSuper = false;
usesEval = false;
usesBackrefOrLastline = false;
// NOTE: bindingHasEscaped is the crucial flag and it effectively is
// unconditionally true whenever it has a call that receives a closure.
// See CallInstr.computeRequiresCallersBindingFlag
bindingHasEscaped =
(this instanceof IREvalScript); // for eval scopes, bindings are considered escaped ...
hasBreakInstrs = false;
hasNonlocalReturns = false;
canReceiveBreaks = false;
canReceiveNonlocalReturns = false;
// recompute flags -- we could be calling this method different times
// definitely once after ir generation and local optimizations propagates constants locally
// but potentially at a later time after doing ssa generation and constant propagation
if (cfg == null) {
computeScopeFlags(false, getInstrs());
} else {
boolean receivesClosureArg = false;
for (BasicBlock b : cfg.getBasicBlocks()) {
receivesClosureArg = computeScopeFlags(receivesClosureArg, b.getInstrs());
}
}
// Compute flags for nested closures (recursively) and set derived flags.
for (IRClosure cl : getClosures()) {
cl.computeScopeFlags();
if (cl.hasBreakInstrs || cl.canReceiveBreaks) {
canReceiveBreaks = true;
}
if (cl.hasNonlocalReturns || cl.canReceiveNonlocalReturns) {
canReceiveNonlocalReturns = true;
}
if (cl.usesZSuper()) {
usesZSuper = true;
}
}
flagsComputed = true;
}
@Override
public Object execute(IRScope scope, Object... data) {
// IRScriptBody do not get explicit call protocol instructions right now.
// They dont push/pop a frame and do other special things like run begin/end blocks.
// So, for now, they go through the runtime stub in IRScriptBody.
//
// Add explicit frame and binding push/pop instrs ONLY for methods -- we cannot handle this in
// closures and evals yet
// If the scope uses $_ or $~ family of vars, has local load/stores, or if its binding has
// escaped, we have
// to allocate a dynamic scope for it and add binding push/pop instructions.
if (explicitCallProtocolSupported(scope)) {
StoreLocalVarPlacementProblem slvpp =
(StoreLocalVarPlacementProblem)
scope.getDataFlowSolution(StoreLocalVarPlacementProblem.NAME);
boolean scopeHasLocalVarStores = false;
boolean bindingHasEscaped = scope.bindingHasEscaped();
CFG cfg = scope.cfg();
if (slvpp != null && bindingHasEscaped) {
scopeHasLocalVarStores = slvpp.scopeHasLocalVarStores();
} else {
// We dont require local-var load/stores to have been run.
// If it is not run, we go conservative and add push/pop binding instrs. everywhere
scopeHasLocalVarStores = bindingHasEscaped;
}
boolean requireFrame = doesItRequireFrame(scope, bindingHasEscaped);
boolean requireBinding = !scope.getFlags().contains(IRFlags.DYNSCOPE_ELIMINATED);
if (requireBinding || requireFrame) {
BasicBlock entryBB = cfg.getEntryBB();
// Push
if (requireFrame) entryBB.addInstr(new PushFrameInstr(scope.getName()));
if (requireBinding) entryBB.addInstr(new PushBindingInstr());
// SSS FIXME: We are doing this conservatively.
// Only scopes that have unrescued exceptions need a GEB.
//
// Allocate GEB if necessary for popping
BasicBlock geb = cfg.getGlobalEnsureBB();
if (geb == null) {
Variable exc = scope.createTemporaryVariable();
geb = new BasicBlock(cfg, Label.getGlobalEnsureBlockLabel());
geb.addInstr(
new ReceiveJRubyExceptionInstr(exc)); // JRuby Implementation exception handling
geb.addInstr(new ThrowExceptionInstr(exc));
cfg.addGlobalEnsureBB(geb);
}
// Pop on all scope-exit paths
for (BasicBlock bb : cfg.getBasicBlocks()) {
Instr i = null;
ListIterator<Instr> instrs = bb.getInstrs().listIterator();
while (instrs.hasNext()) {
i = instrs.next();
// Right now, we only support explicit call protocol on methods.
// So, non-local returns and breaks don't get here.
// Non-local-returns and breaks are tricky since they almost always
// throw an exception and we don't multiple pops (once before the
// return/break, and once when the exception is caught).
if (!bb.isExitBB() && i instanceof ReturnBase) {
// Add before the break/return
instrs.previous();
if (requireBinding) instrs.add(new PopBindingInstr());
if (requireFrame) instrs.add(new PopFrameInstr());
break;
}
}
if (bb.isExitBB() && !bb.isEmpty()) {
// Last instr could be a return -- so, move iterator one position back
if (i != null && i instanceof ReturnBase) instrs.previous();
if (requireBinding) instrs.add(new PopBindingInstr());
if (requireFrame) instrs.add(new PopFrameInstr());
}
if (bb == geb) {
// Add before throw-exception-instr which would be the last instr
if (i != null) {
// Assumption: Last instr should always be a control-transfer instruction
assert i.getOperation().transfersControl()
: "Last instruction of GEB in scope: "
+ scope
+ " is "
+ i
+ ", not a control-xfer instruction";
instrs.previous();
}
if (requireBinding) instrs.add(new PopBindingInstr());
if (requireFrame) instrs.add(new PopFrameInstr());
}
}
}
// This scope has an explicit call protocol flag now
scope.setExplicitCallProtocolFlag();
}
// FIXME: Useless for now
// Run on all nested closures.
for (IRClosure c : scope.getClosures()) run(c, false, true);
// LVA information is no longer valid after the pass
// FIXME: Grrr ... this seems broken to have to create a new object to invalidate
(new LiveVariableAnalysis()).invalidate(scope);
return null;
}