Emit less garbage without opts, if it has no side effects (#1141)

Author: Frotty

de.peeeq.wurstscript/src/main/java/de/peeeq/wurstio/WurstCompilerJassImpl.java

@@ -563,6 +563,11 @@ public JassProg transformProgToJass() {
         // translate flattened intermediate lang to jass:
 
         beginPhase(14, "translate to jass");
+        optimizer.removeGarbage();
+        imProg.flatten(imTranslator);
+        imTranslator.removeEmptyPackageInits();
+        optimizer.removeGarbage();
+        imProg.flatten(imTranslator);
         getImTranslator().calculateCallRelationsAndReadVariables();
         ImToJassTranslator translator =
             new ImToJassTranslator(getImProg(), getImTranslator().getCalledFunctions(), getImTranslator().getMainFunc(), getImTranslator().getConfFunc());

de.peeeq.wurstscript/src/main/java/de/peeeq/wurstscript/intermediatelang/optimizer/SideEffectAnalyzer.java

@@ -8,8 +8,11 @@
 import de.peeeq.wurstscript.translation.imtranslation.ImHelper;
 
 import java.util.Collection;
+import java.util.HashMap;
 import java.util.LinkedHashSet;
+import java.util.Map;
 import java.util.Set;
+import java.util.function.Predicate;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
@@ -455,4 +458,123 @@ public boolean hasSideEffects(Element elem) {
         Set<ImVar> imVars = directlySetVariables(elem);
         return natives.size() + directFuncs.size() + imVars.size() > 0;
     }
+
+    /**
+     * Checks if the given element has observable side effects.
+     * Pure natives can be configured via the predicate.
+     */
+    public boolean hasObservableSideEffects(Element elem, Predicate<ImFunction> isNativeWithoutSideEffects) {
+        return new ObservableSideEffectChecker(isNativeWithoutSideEffects).hasSideEffects(elem);
+    }
+
+    private final class ObservableSideEffectChecker {
+        private final Predicate<ImFunction> isNativeWithoutSideEffects;
+        private final Map<ImFunction, Boolean> cache = new HashMap<>();
+        private final Set<ImFunction> inProgress = new LinkedHashSet<>();
+
+        private ObservableSideEffectChecker(Predicate<ImFunction> isNativeWithoutSideEffects) {
+            this.isNativeWithoutSideEffects = isNativeWithoutSideEffects;
+        }
+
+        private boolean hasSideEffects(Element elem) {
+            if (!directlySetVariables(elem).isEmpty()) {
+                return true;
+            }
+            for (ImFunction nativeFunc : calledNatives(elem)) {
+                if (!isNativeWithoutSideEffects.test(nativeFunc)) {
+                    return true;
+                }
+            }
+            for (ImFunction called : calledFunctions(elem)) {
+                if (functionHasSideEffects(called)) {
+                    return true;
+                }
+            }
+            return false;
+        }
+
+        private boolean functionHasSideEffects(ImFunction func) {
+            Boolean cached = cache.get(func);
+            if (cached != null) {
+                return cached;
+            }
+            if (func.isNative()) {
+                boolean sideEffect = !isNativeWithoutSideEffects.test(func);
+                cache.put(func, sideEffect);
+                return sideEffect;
+            }
+            if (func.isExtern()) {
+                // Extern implementations are not represented in IM and may have runtime effects.
+                cache.put(func, true);
+                return true;
+            }
+            if (!inProgress.add(func)) {
+                return true;
+            }
+            boolean sideEffect = hasGlobalSideEffects(func.getBody());
+            inProgress.remove(func);
+            cache.put(func, sideEffect);
+            return sideEffect;
+        }
+
+        private boolean hasGlobalSideEffects(Element elem) {
+            if (hasMemberWrites(elem)) {
+                return true;
+            }
+            for (ImVar var : directlySetVariables(elem)) {
+                // Some optimization passes temporarily detach vars; in that state isGlobal() throws.
+                if (isAttachedGlobal(var)) {
+                    return true;
+                }
+            }
+            for (ImFunction nativeFunc : calledNatives(elem)) {
+                if (!isNativeWithoutSideEffects.test(nativeFunc)) {
+                    return true;
+                }
+            }
+            for (ImFunction called : calledFunctions(elem)) {
+                if (functionHasSideEffects(called)) {
+                    return true;
+                }
+            }
+            return false;
+        }
+
+        private boolean hasMemberWrites(Element elem) {
+            final boolean[] foundMemberWrite = {false};
+            elem.accept(new ImStmt.DefaultVisitor() {
+                @Override
+                public void visit(ImSet set) {
+                    super.visit(set);
+                    if (isMemberWrite(set.getLeft())) {
+                        foundMemberWrite[0] = true;
+                    }
+                }
+
+                private boolean isMemberWrite(ImLExpr left) {
+                    if (left instanceof ImMemberAccess) {
+                        return true;
+                    }
+                    if (left instanceof ImTupleSelection) {
+                        ImExpr tupleExpr = ((ImTupleSelection) left).getTupleExpr();
+                        return tupleExpr instanceof ImLExpr && isMemberWrite((ImLExpr) tupleExpr);
+                    }
+                    if (left instanceof ImTupleExpr) {
+                        for (ImExpr expr : ((ImTupleExpr) left).getExprs()) {
+                            if (expr instanceof ImLExpr && isMemberWrite((ImLExpr) expr)) {
+                                return true;
+                            }
+                        }
+                    }
+                    return false;
+                }
+            });
+            return foundMemberWrite[0];
+        }
+
+        private boolean isAttachedGlobal(ImVar var) {
+            Element parent = var.getParent();
+            return parent != null && parent.getParent() instanceof ImProg;
+        }
+    }
 }

de.peeeq.wurstscript/src/main/java/de/peeeq/wurstscript/translation/imoptimizer/ImOptimizer.java

@@ -2,10 +2,12 @@
 
 import com.google.common.collect.Lists;
 import de.peeeq.wurstio.TimeTaker;
+import de.peeeq.wurstscript.WurstOperator;
 import de.peeeq.wurstscript.WLogger;
 import de.peeeq.wurstscript.intermediatelang.optimizer.BranchMerger;
 import de.peeeq.wurstscript.intermediatelang.optimizer.ConstantAndCopyPropagation;
 import de.peeeq.wurstscript.intermediatelang.optimizer.LocalMerger;
+import de.peeeq.wurstscript.intermediatelang.optimizer.SideEffectAnalyzer;
 import de.peeeq.wurstscript.intermediatelang.optimizer.SimpleRewrites;
 import de.peeeq.wurstscript.jassIm.*;
 import de.peeeq.wurstscript.translation.imtranslation.ImHelper;
@@ -102,6 +104,7 @@ public boolean removeGarbage() {
             trans.calculateCallRelationsAndReadVariables();
             final Set<ImVar> readVars = trans.getReadVariables();
             final Set<ImFunction> usedFuncs = trans.getUsedFunctions();
+            SideEffectAnalyzer sideEffectAnalyzer = new SideEffectAnalyzer(prog);
 
             // keep only used variables
             int globalsBefore = prog.getGlobals().size();
@@ -142,25 +145,30 @@ public void visit(ImSet e) {
                         if (e.getLeft() instanceof ImVarAccess) {
                             ImVarAccess va = (ImVarAccess) e.getLeft();
                             if (!readVars.contains(va.getVar()) && !TRVEHelper.protectedVariables.contains(va.getVar().getName())) {
-                                replacements.add(Pair.create(e, Collections.singletonList(e.getRight())));
+                                List<ImExpr> sideEffects = collectSideEffects(e.getRight(), sideEffectAnalyzer);
+                                replacements.add(Pair.create(e, sideEffects));
                             }
                         } else if (e.getLeft() instanceof ImVarArrayAccess) {
                             ImVarArrayAccess va = (ImVarArrayAccess) e.getLeft();
                             if (!readVars.contains(va.getVar()) && !TRVEHelper.protectedVariables.contains(va.getVar().getName())) {
-                                // IMPORTANT: removeAll() clears parent references
-                                List<ImExpr> exprs = va.getIndexes().removeAll();
-                                exprs.add(e.getRight());
+                                List<ImExpr> exprs = new ArrayList<>();
+                                for (ImExpr index : va.getIndexes()) {
+                                    exprs.addAll(collectSideEffects(index, sideEffectAnalyzer));
+                                }
+                                exprs.addAll(collectSideEffects(e.getRight(), sideEffectAnalyzer));
                                 replacements.add(Pair.create(e, exprs));
                             }
                         } else if (e.getLeft() instanceof ImTupleSelection) {
                             ImVar var = TypesHelper.getTupleVar((ImTupleSelection) e.getLeft());
                             if(var != null && !readVars.contains(var) && !TRVEHelper.protectedVariables.contains(var.getName())) {
-                                replacements.add(Pair.create(e, Collections.singletonList(e.getRight())));
+                                List<ImExpr> sideEffects = collectSideEffects(e.getRight(), sideEffectAnalyzer);
+                                replacements.add(Pair.create(e, sideEffects));
                             }
                         } else if(e.getLeft() instanceof ImMemberAccess) {
                             ImMemberAccess va = ((ImMemberAccess) e.getLeft());
                             if (!readVars.contains(va.getVar()) && !TRVEHelper.protectedVariables.contains(va.getVar().getName())) {
-                                replacements.add(Pair.create(e, Collections.singletonList(e.getRight())));
+                                List<ImExpr> sideEffects = collectSideEffects(e.getRight(), sideEffectAnalyzer);
+                                replacements.add(Pair.create(e, sideEffects));
                             }
                         }
                     }
@@ -170,7 +178,9 @@ public void visit(ImSet e) {
                 for (Pair<ImStmt, List<ImExpr>> pair : replacements) {
                     changes = true;
                     ImExpr r;
-                    if (pair.getB().size() == 1) {
+                    if (pair.getB().isEmpty()) {
+                        r = ImHelper.statementExprVoid(JassIm.ImStmts());
+                    } else if (pair.getB().size() == 1) {
                         r = pair.getB().get(0);
                         // CRITICAL: Clear parent before reusing the node
                         r.setParent(null);
@@ -194,4 +204,76 @@ public void visit(ImSet e) {
         }
         return anyChanges;
     }
+
+    private List<ImExpr> collectSideEffects(ImExpr expr, SideEffectAnalyzer analyzer) {
+        if (expr == null) {
+            return Collections.emptyList();
+        }
+        if (mayTrapAtRuntime(expr)) {
+            return Collections.singletonList(expr);
+        }
+        if (analyzer.hasObservableSideEffects(expr, func -> func.isNative()
+            && UselessFunctionCallsRemover.isFunctionWithoutSideEffect(func.getName()))) {
+            return Collections.singletonList(expr);
+        }
+        return Collections.emptyList();
+    }
+
+    private boolean mayTrapAtRuntime(Element elem) {
+        return mayTrapAtRuntime(elem, new HashMap<>(), new LinkedHashSet<>());
+    }
+
+    private boolean mayTrapAtRuntime(Element elem, Map<ImFunction, Boolean> functionCache, Set<ImFunction> inProgress) {
+        if (elem instanceof ImFunctionCall) {
+            ImFunction calledFunc = ((ImFunctionCall) elem).getFunc();
+            if (functionMayTrapAtRuntime(calledFunc, functionCache, inProgress)) {
+                return true;
+            }
+        } else if (elem instanceof ImMethodCall) {
+            ImFunction calledFunc = ((ImMethodCall) elem).getMethod().getImplementation();
+            if (calledFunc == null || functionMayTrapAtRuntime(calledFunc, functionCache, inProgress)) {
+                return true;
+            }
+        }
+
+        if (elem instanceof ImOperatorCall) {
+            ImOperatorCall opCall = (ImOperatorCall) elem;
+            WurstOperator op = opCall.getOp();
+            if ((op == WurstOperator.DIV_INT || op == WurstOperator.MOD_INT) && opCall.getArguments().size() >= 2) {
+                ImExpr denominator = opCall.getArguments().get(1);
+                // Preserve integer div/mod unless denominator is provably non-zero.
+                if (!(denominator instanceof ImIntVal) || ((ImIntVal) denominator).getValI() == 0) {
+                    return true;
+                }
+            }
+        }
+        for (int i = 0; i < elem.size(); i++) {
+            Element child = elem.get(i);
+            if (mayTrapAtRuntime(child, functionCache, inProgress)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private boolean functionMayTrapAtRuntime(ImFunction function, Map<ImFunction, Boolean> functionCache, Set<ImFunction> inProgress) {
+        if (function.isNative()) {
+            return false;
+        }
+
+        Boolean cachedResult = functionCache.get(function);
+        if (cachedResult != null) {
+            return cachedResult;
+        }
+
+        if (!inProgress.add(function)) {
+            // Recursive cycles are conservatively treated as potentially trapping.
+            return true;
+        }
+
+        boolean mayTrap = mayTrapAtRuntime(function.getBody(), functionCache, inProgress);
+        inProgress.remove(function);
+        functionCache.put(function, mayTrap);
+        return mayTrap;
+    }
 }

de.peeeq.wurstscript/src/main/java/de/peeeq/wurstscript/translation/imtranslation/EliminateTuples.java

@@ -455,6 +455,29 @@ private static ImStatementExpr inSet(ImSet imSet, ImFunction f) {
                 + "\nLHS=" + left + "\nRHS=" + right);
         }
 
+        boolean allLiteral = true;
+        for (ImExpr r : rhsLeaves) {
+            if (!isSimpleLiteral(r)) {
+                allLiteral = false;
+                break;
+            }
+        }
+
+        if (allLiteral) {
+            for (int i = 0; i < lhsLeaves.size(); i++) {
+                ImLExpr l = lhsLeaves.get(i);
+                ImType targetT = l.attrTyp();
+                ImExpr r = rhsLeaves.get(i);
+                if (r instanceof ImNull) {
+                    r = ImHelper.defaultValueForComplexType(targetT);
+                }
+                l.setParent(null);
+                r.setParent(null);
+                stmts.add(JassIm.ImSet(imSet.getTrace(), l, r));
+            }
+            return ImHelper.statementExprVoid(stmts);
+        }
+
         // 4) Evaluate RHS leaves first into temps (preserve side-effect order & alias safety)
         List<ImVar> temps = new ArrayList<>(rhsLeaves.size());
         for (int i = 0; i < rhsLeaves.size(); i++) {
@@ -485,6 +508,14 @@ private static ImStatementExpr inSet(ImSet imSet, ImFunction f) {
         return ImHelper.statementExprVoid(stmts);
     }
 
+    private static boolean isSimpleLiteral(ImExpr expr) {
+        return expr instanceof ImBoolVal
+            || expr instanceof ImIntVal
+            || expr instanceof ImRealVal
+            || expr instanceof ImStringVal
+            || expr instanceof ImNull;
+    }
+
     /** Flatten LHS recursively into addressable leaves (ImLExpr), hoisting side-effects */
     private static void flattenLhsTuple(ImExpr e, List<ImLExpr> out, ImStmts sideStmts) {
         ImExpr x = extractSideEffect(e, sideStmts);