package org.jruby.ir.dataflow.analyses;
import org.jruby.ir.IRClosure;
import org.jruby.ir.IRScope;
import org.jruby.ir.Operation;
import org.jruby.ir.dataflow.DataFlowConstants;
import org.jruby.ir.dataflow.FlowGraphNode;
import org.jruby.ir.instructions.*;
import org.jruby.ir.operands.*;
import org.jruby.ir.representations.BasicBlock;
import org.jruby.ir.util.Edge;
import java.util.HashSet;
import java.util.ListIterator;
import java.util.Map;
import java.util.Set;
public class StoreLocalVarPlacementNode extends FlowGraphNode<StoreLocalVarPlacementProblem, StoreLocalVarPlacementNode> {
public StoreLocalVarPlacementNode(StoreLocalVarPlacementProblem prob, BasicBlock n) {
super(prob, n);
}
@Override
public void init() {
outDirtyVars = new HashSet<LocalVariable>();
// For rescue entries, we allocate <in> once and never clear it on each pass.
if (getBB().isRescueEntry()) inDirtyVars = new HashSet<LocalVariable>();
}
@Override
public void buildDataFlowVars(Instr i) {
// Nothing to do -- because we are going to simply use non-closure, non-self, non-block LocalVariables as our data flow variables
// rather than build a new data flow type for it
}
@Override
public void applyPreMeetHandler() {
// For rescue entries, <in> is handled specially
if (!getBB().isRescueEntry()) inDirtyVars = new HashSet<LocalVariable>();
}
@Override
public void compute_MEET(Edge e, StoreLocalVarPlacementNode pred) {
// Ignore rescue entries -- dirty vars are handled specially for these
if (!pred.basicBlock.isRescueEntry()) inDirtyVars.addAll(pred.outDirtyVars);
}
@Override
public void initSolution() {
dirtyVars = new HashSet<LocalVariable>(inDirtyVars);
}
@Override
public void applyTransferFunction(Instr i) {
IRScope scope = problem.getScope();
boolean scopeBindingHasEscaped = scope.bindingHasEscaped();
// Process closure accepting instrs specially -- these are the sites of binding stores!
if (i instanceof ClosureAcceptingInstr) {
Operand o = ((ClosureAcceptingInstr)i).getClosureArg();
// At this site, a binding will get allocated if it has not been already!
if (o != null && o instanceof WrappedIRClosure) {
// In this first pass, the current scope and the call's closure are considered
// independent of each other which means any variable that is used by the variable
// will get spilled into the binding. This is clearly conservative, but simplifies
// the analysis.
IRClosure cl = ((WrappedIRClosure) o).getClosure();
// If the call is a dataflow barrier, we have to spill everything here
boolean spillAllVars = scopeBindingHasEscaped;
// - If all variables have to be spilled, then those variables will no longer be dirty after the call site
// - If a variable is used in the closure (FIXME: Strictly only those vars that are live at the call site --
// but we dont have this info!), it has to be spilt. So, these variables are no longer dirty after the call site.
// - If a variable is (re)defined in the closure, it will always be loaded after the call. So, we have to always
// spill it before the call in the scenario that the closure never gets executed! So, it won't be dirty after
// the call site.
Set<LocalVariable> newDirtyVars = new HashSet<LocalVariable>(dirtyVars);
for (LocalVariable v : dirtyVars) {
if (spillAllVars || cl.usesLocalVariable(v) || cl.definesLocalVariable(v)) {
newDirtyVars.remove(v);
}
}
dirtyVars = newDirtyVars;
} else if (scopeBindingHasEscaped) { // Call has no closure && it requires stores
dirtyVars.clear();
} else {
// All variables not local to the current scope have to be always spilled because of
// multi-threading scenarios where some other scope could load this variable concurrently.
//
// Allocate a new hash-set and modify it to get around ConcurrentModificationException on dirtyVars
Set<LocalVariable> newDirtyVars = new HashSet<LocalVariable>(dirtyVars);
for (LocalVariable v : dirtyVars) {
if ((v instanceof ClosureLocalVariable) && ((ClosureLocalVariable)v).definingScope != scope) {
newDirtyVars.remove(v);
}
}
dirtyVars = newDirtyVars;
}
}
if (scopeBindingHasEscaped && (i.getOperation() == Operation.PUT_GLOBAL_VAR)) {
// global-var tracing can execute closures set up in previous trace-var calls
// in which case we would have the 'scopeBindingHasEscaped' flag set to true
dirtyVars.clear();
}
// If this instruction can raise an exception and we are going to be rescued,
// spill all dirty vars before the instruction!
if (i.canRaiseException() && hasExceptionsRescued()) {
dirtyVars.clear();
}
if (i instanceof ResultInstr) {
Variable v = ((ResultInstr) i).getResult();
// %self is local to every scope and never crosses scope boundaries and need not be spilled/refilled
if (v instanceof LocalVariable && !v.isSelf()) dirtyVars.add((LocalVariable) v);
}
if (i.getOperation().isReturn()) dirtyVars.clear();
}
@Override
public boolean solutionChanged() {
return !outDirtyVars.equals(dirtyVars);
}
@Override
public void finalizeSolution() {
outDirtyVars = dirtyVars;
}
@Override
public String toString() {
return "";
}
public boolean addStores(Map<Operand, Operand> varRenameMap, Set<LocalVariable> excTargetDirtyVars) {
IRScope scope = problem.getScope();
boolean addedStores = false;
boolean isClosure = scope instanceof IRClosure;
boolean scopeBindingHasEscaped = scope.bindingHasEscaped();
ListIterator<Instr> instrs = basicBlock.getInstrs().listIterator();
initSolution();
// If this is the exit BB, we need a binding store on exit only for vars that are both:
//
// (a) dirty,
// (b) live on exit from the closure
// condition reqd. because the variable could be dirty but not used outside.
// Ex: s=0; a.each { |i| j = i+1; sum += j; }; puts sum
// i,j are dirty inside the block, but not used outside
if (basicBlock.isExitBB()) {
LiveVariablesProblem lvp = (LiveVariablesProblem)scope.getDataFlowSolution(DataFlowConstants.LVP_NAME);
java.util.Collection<LocalVariable> liveVars = lvp.getVarsLiveOnScopeExit();
if (liveVars != null) {
dirtyVars.retainAll(liveVars); // Intersection with variables live on exit from the scope
} else {
dirtyVars.clear();
}
}
while (instrs.hasNext()) {
Instr i = instrs.next();
// Process closure accepting instrs specially -- these are the sites of binding stores!
if (i instanceof ClosureAcceptingInstr) {
Operand o = ((ClosureAcceptingInstr)i).getClosureArg();
if (o != null && o instanceof WrappedIRClosure) {
IRClosure cl = ((WrappedIRClosure) o).getClosure();
// Add before call -- hence instrs.previous & instrs.next
instrs.previous();
// If the call is a dataflow barrier, we have to spill everything here
boolean spillAllVars = scopeBindingHasEscaped;
// Unless we have to spill everything, spill only those dirty variables that are:
// - used in the closure (FIXME: Strictly only those vars that are live at the call site -- but we dont have this info!)
Set<LocalVariable> newDirtyVars = new HashSet<LocalVariable>(dirtyVars);
for (LocalVariable v : dirtyVars) {
// We have to spill the var that is defined in the closure as well because the load var pass
// will attempt to load the var always. So, if the call doesn't actually call the closure,
// we'll be in trouble in that scenario!
if (spillAllVars || cl.usesLocalVariable(v) || cl.definesLocalVariable(v)) {
addedStores = true;
instrs.add(new StoreLocalVarInstr(problem.getLocalVarReplacement(v, varRenameMap), scope, v));
newDirtyVars.remove(v);
}
}
dirtyVars = newDirtyVars;
instrs.next();
} else if (scopeBindingHasEscaped) { // Call has no closure && it requires stores
// Add before call -- hence instrs.previous & instrs.next
instrs.previous();
for (LocalVariable v : dirtyVars) {
addedStores = true;
instrs.add(new StoreLocalVarInstr(problem.getLocalVarReplacement(v, varRenameMap), scope, v));
}
instrs.next();
dirtyVars.clear();
} else {
instrs.previous();
// All variables not local to the current scope have to be always spilled because of
// multi-threading scenarios where some other scope could load this variable concurrently.
//
// Allocate a new hash-set and modify it to get around ConcurrentModificationException on dirtyVars
Set<LocalVariable> newDirtyVars = new HashSet<LocalVariable>(dirtyVars);
for (LocalVariable v : dirtyVars) {
// SSS FIXME: I guess we cannot use v.getScopeDepth() > 0 because the variable could be a cloned
// instance from a different depth and that could mislead us. See if there is a way to fix this.
// If we introduced 'definingScope' in all local variables, we could simply check for scope match
// without the instanceof check here.
if ( (v instanceof ClosureLocalVariable && ((ClosureLocalVariable)v).definingScope != scope)
|| (!(v instanceof ClosureLocalVariable) && scope.getScopeType().isClosureType()))
{
addedStores = true;
instrs.add(new StoreLocalVarInstr(problem.getLocalVarReplacement(v, varRenameMap), scope, v));
newDirtyVars.remove(v);
}
}
dirtyVars = newDirtyVars;
instrs.next();
}
} else if ((isClosure && (i instanceof ReturnInstr)) || (i instanceof BreakInstr)) {
// At closure return and break instructions (both of which are exits from the closure),
// we need a binding store on exit only for vars that are both:
//
// (a) dirty,
// (b) live on exit from the closure
// condition reqd. because the variable could be dirty but not used outside.
// Ex: s=0; a.each { |i| j = i+1; sum += j; return if j < 5; sum += 1; }; puts sum
// i,j are dirty inside the block, but not used outside
//
// If this also happens to be exit BB, we would have intersected already earlier -- so no need to do it again!
if (!basicBlock.isExitBB()) {
LiveVariablesProblem lvp = (LiveVariablesProblem)scope.getDataFlowSolution(DataFlowConstants.LVP_NAME);
if (lvp == null) {
System.out.println("LVP missing for " + scope);
}
java.util.Collection<LocalVariable> liveVars = lvp.getVarsLiveOnScopeExit();
if (liveVars != null) {
dirtyVars.retainAll(liveVars); // Intersection with variables live on exit from the scope
} else {
dirtyVars.clear();
}
}
// Add before call
instrs.previous();
boolean f = problem.addClosureExitStoreLocalVars(instrs, dirtyVars, varRenameMap);
addedStores = addedStores || f;
instrs.next();
// Nothing is dirty anymore -- everything that needs spilling has been spilt
dirtyVars.clear();
}
if (scopeBindingHasEscaped && (i.getOperation() == Operation.PUT_GLOBAL_VAR)) {
// global-var tracing can execute closures set up in previous trace-var calls
// in which case we would have the 'scopeBindingHasEscaped' flag set to true
instrs.previous();
for (LocalVariable v : dirtyVars) {
addedStores = true;
instrs.add(new StoreLocalVarInstr(problem.getLocalVarReplacement(v, varRenameMap), scope, v));
}
instrs.next();
dirtyVars.clear();
}
if (i.canRaiseException()) {
if (hasExceptionsRescued()) {
// If exceptions will be rescued, spill every dirty var here
// Add before excepting instr -- hence instrs.previous & instrs.next
instrs.previous();
for (LocalVariable v : dirtyVars) {
addedStores = true;
instrs.add(new StoreLocalVarInstr(problem.getLocalVarReplacement(v, varRenameMap), scope, v));
}
instrs.next();
dirtyVars.clear();
} else if (excTargetDirtyVars != null) {
// If exceptions won't be rescued, pass them back to be spilled in the global ensure block
excTargetDirtyVars.addAll(dirtyVars);
}
}
if (i instanceof ResultInstr) {
Variable v = ((ResultInstr) i).getResult();
// %self is local to every scope and never crosses scope boundaries and need not be spilled/refilled
if (v instanceof LocalVariable && !v.isSelf()) {
LocalVariable lv = (LocalVariable) v;
dirtyVars.add(lv);
// Make sure there is a replacement tmp-var allocated for lv
problem.getLocalVarReplacement(lv, varRenameMap);
}
}
}
// If this is the exit BB, add binding stores for all vars that are still dirty
if (basicBlock.isExitBB()) {
// Last instr could be a return -- so, move iterator one position back
if (instrs.hasPrevious()) instrs.previous();
boolean f = problem.addClosureExitStoreLocalVars(instrs, dirtyVars, varRenameMap);
addedStores = addedStores || f;
}
return addedStores;
}
Set<LocalVariable> inDirtyVars; // On entry to flow graph node: Variables that need to be stored to the heap binding
Set<LocalVariable> outDirtyVars; // On exit from flow graph node: Variables that need to be stored to the heap binding
Set<LocalVariable> dirtyVars; // Temporary state while applying transfer function
}