package org.jruby.ir.passes;
import org.jruby.ir.IRClosure;
import org.jruby.ir.IRScope;
import org.jruby.ir.Operation;
import org.jruby.ir.instructions.CopyInstr;
import org.jruby.ir.instructions.Instr;
import org.jruby.ir.instructions.ResultInstr;
import org.jruby.ir.operands.Operand;
import org.jruby.ir.operands.Variable;
import org.jruby.ir.representations.BasicBlock;
import org.jruby.ir.representations.CFG;
import java.util.*;
public class LocalOptimizationPass extends CompilerPass {
public static List<Class<? extends CompilerPass>> DEPENDENCIES = Arrays.<Class<? extends CompilerPass>>asList(CFGBuilder.class);
@Override
public String getLabel() {
return "Local Optimizations";
}
@Override
public List<Class<? extends CompilerPass>> getDependencies() {
return DEPENDENCIES;
}
@Override
public Object execute(IRScope s, Object... data) {
// This let us compute execute scope flags for a method based on what all nested closures do
for (IRClosure c: s.getClosures()) {
run(c, false, true);
}
for (BasicBlock b: ((CFG) data[0]).getBasicBlocks()) {
runLocalOptsOnInstrList(s, b.getInstrs().listIterator(), false);
}
// SSS FIXME: What is this about?
// Why 'Only after running local opts'? Figure out and document.
//
// Only after running local opts, compute various execution scope flags.
s.computeScopeFlags();
// LVA information is no longer valid after this pass
// Currently, we don't run this after LVA, but just in case ...
//
// FIXME: Grrr ... this seems broken to have to create a new object to invalidate
(new LiveVariableAnalysis()).invalidate(s);
return null;
}
private static void recordSimplification(Variable res, Operand val, Map<Operand, Operand> valueMap, Map<Variable, List<Variable>> simplificationMap) {
valueMap.put(res, val);
// For all variables used by val, record a reverse mapping to let us track
// Read-After-Write scenarios when any of these variables are modified.
List<Variable> valVars = new ArrayList<Variable>();
val.addUsedVariables(valVars);
for (Variable v: valVars) {
List<Variable> x = simplificationMap.get(v);
if (x == null) {
x = new ArrayList<Variable>();
simplificationMap.put(v, x);
}
x.add(res);
}
}
public static void runLocalOptsOnInstrList(IRScope s, ListIterator<Instr> instrs, boolean preCFG) {
// Reset value map if this instruction is the start/end of a basic block
Map<Operand,Operand> valueMap = new HashMap<Operand,Operand>();
Map<Variable,List<Variable>> simplificationMap = new HashMap<Variable,List<Variable>>();
while (instrs.hasNext()) {
Instr i = instrs.next();
Operation iop = i.getOperation();
if (preCFG && iop.startsBasicBlock()) {
valueMap = new HashMap<Operand,Operand>();
simplificationMap = new HashMap<Variable,List<Variable>>();
}
// Simplify instruction and record mapping between target variable and simplified value
// System.out.println("BEFORE: " + i);
Operand val = i.simplifyAndGetResult(s, valueMap);
// FIXME: This logic can be simplified based on the number of res != null checks only done if doesn't
Variable res = i instanceof ResultInstr ? ((ResultInstr) i).getResult() : null;
// System.out.println("AFTER: " + i + "; dst = " + res + "; val = " + val);
if (res != null && val != null) {
if (!res.equals(val)) {
recordSimplification(res, val, valueMap, simplificationMap);
}
if (!i.hasSideEffects()) {
if (i instanceof CopyInstr) {
if (res.equals(val) && i.canBeDeleted(s)) {
i.markDead();
instrs.remove();
}
} else {
instrs.set(new CopyInstr(res, val));
}
}
} else if (res != null && val == null) {
// If we didn't get a simplified value, remove any existing simplifications for the result
// to get rid of RAW hazards!
valueMap.remove(res);
}
// Purge all entries in valueMap that have 'res' as their simplified value to take care of RAW scenarios (because we aren't in SSA form yet!)
if (res != null && !res.equals(val)) {
List<Variable> simplifiedVars = simplificationMap.get(res);
if (simplifiedVars != null) {
for (Variable v: simplifiedVars) {
valueMap.remove(v);
}
simplificationMap.remove(res);
}
}
// If the call has been optimized away in the previous step, it is no longer a hard boundary for opts!
//
// Right now, calls are considered hard boundaries for optimization and
// information cannot be propagated across them!
//
// SSS FIXME: Rather than treat all calls with a broad brush, what we need
// is to capture different attributes about a call :
// - uses closures
// - known call target
// - can modify scope,
// - etc.
//
// This information is present in instruction flags on CallBase. Use it!
if ((preCFG && iop.endsBasicBlock()) || (iop.isCall() && !i.isDead())) {
valueMap = new HashMap<Operand,Operand>();
simplificationMap = new HashMap<Variable,List<Variable>>();
}
}
}
}