dart2js cps: Refactor tracking of side effects.

pkg/compiler/lib/src/cps_ir/loop_effects.dart

 library dart2js.cps_ir.loop_effects;
 
 import 'cps_ir_nodes.dart';
 import 'loop_hierarchy.dart';
-import '../universe/side_effects.dart';
-import '../elements/elements.dart';
 import '../world.dart';
+import 'effects.dart';
 
-/// Determines which the [SideEffects] that may occur during each loop in
-/// a given function, in addition to whether the loop may change the length
-/// of an indexable object.
-///
-/// TODO(asgerf): Make length a flag on [SideEffects] for better precision and
-/// so we don't need to special case the length in this class.
+/// Determines the side effects that may occur in each loop.
 class LoopSideEffects extends TrampolineRecursiveVisitor {
   LoopHierarchy loopHierarchy;
   final World world;
   final Map<Continuation, List<Continuation>> exitContinuations = {};
-  final Map<Continuation, SideEffects> loopSideEffects = {};
-  final Set<Continuation> loopsChangingLength = new Set<Continuation>();
+  final Map<Continuation, int> loopSideEffects = {};
   Continuation currentLoopHeader;
-  SideEffects currentLoopSideEffects = new SideEffects.empty();
-  bool currentLoopChangesLength = false;
 
   LoopSideEffects(FunctionDefinition node, this.world, {this.loopHierarchy}) {
     if (loopHierarchy == null) {
       loopHierarchy = new LoopHierarchy(node);
     }
     visit(node);
   }
 
   /// Returns the accumulated effects and dependencies on all paths from the
   /// loop entry to any recursive invocation of the loop.
-  SideEffects getSideEffectsInLoop(Continuation loop) {
+  int getSideEffectsInLoop(Continuation loop) {
     return loopSideEffects[loop];
   }
 
   /// True if the length of an indexable object may change between the loop
   /// entry and a recursive invocation of the loop.
-  bool loopChangesLength(Continuation loop) {
-    return loopsChangingLength.contains(loop);
+  bool changesIndexableLength(Continuation loop) {
+    return loopSideEffects[loop] & Effects.changesIndexableLength != 0;
   }
 
   @override
   Expression traverseContinuation(Continuation cont) {
     if (cont.isRecursive) {
-      SideEffects oldEffects = currentLoopSideEffects;
-      bool oldChangesLength = currentLoopChangesLength;
-      loopSideEffects[cont] = currentLoopSideEffects = new SideEffects.empty();
+      loopSideEffects[cont] = Effects.none;
       exitContinuations[cont] = <Continuation>[];
       pushAction(() {
-        oldEffects.add(currentLoopSideEffects);
-        if (currentLoopChangesLength) {
-          loopsChangingLength.add(cont);
+        if (currentLoopHeader != null) {
+          loopSideEffects[currentLoopHeader] |= loopSideEffects[cont];
         }
-        currentLoopChangesLength = currentLoopChangesLength || oldChangesLength;
-        currentLoopSideEffects = oldEffects;
         exitContinuations[cont].forEach(push);
       });
     }
     Continuation oldLoopHeader = currentLoopHeader;
     currentLoopHeader = loopHierarchy.getLoopHeader(cont);
     pushAction(() {
       currentLoopHeader = oldLoopHeader;
     });
     return cont.body;
   }
 
   @override
   Expression traverseLetHandler(LetHandler node) {
     enqueueContinuation(node.handler);
     return node.body;
   }
 
   @override
   Expression traverseLetCont(LetCont node) {
     node.continuations.forEach(enqueueContinuation);
     return node.body;
   }
 
+  @override
+  Expression traverseLetPrim(LetPrim node) {
+    if (currentLoopHeader != null) {
+      loopSideEffects[currentLoopHeader] |= node.primitive.effectFlags;
+    }
+    return node.body;
+  }
+
   void enqueueContinuation(Continuation cont) {
     Continuation loop = loopHierarchy.getEnclosingLoop(cont);
     if (loop == currentLoopHeader) {
       push(cont);
     } else {
       // Multiple loops can be exited at once.
       // Register as an exit from the outermost loop being exited.
       Continuation inner = currentLoopHeader;
       Continuation outer = loopHierarchy.getEnclosingLoop(currentLoopHeader);
       while (outer != loop) {
         if (inner == null) {
           // The shrinking reductions pass must run before any pass that relies
           // on computing loop side effects.
           world.compiler.reporter.internalError(null,
               'Unreachable continuations must be removed before computing '
               'loop side effects.');
         }
         inner = outer;
         outer = loopHierarchy.getEnclosingLoop(outer);
       }
       exitContinuations[inner].add(cont);
     }
   }
-
-  void addSideEffects(SideEffects effects) {
-    currentLoopSideEffects.add(effects);
-    if (effects.changesIndex()) {
-      currentLoopChangesLength = true;
-    }
-  }
-
-  void addAllSideEffects() {
-    currentLoopSideEffects.setAllSideEffects();
-    currentLoopSideEffects.setDependsOnSomething();
-    currentLoopChangesLength = true;
-  }
-
-  void visitInvokeMethod(InvokeMethod node) {
-    addSideEffects(world.getSideEffectsOfSelector(node.selector, node.mask));
-  }
-
-  void visitInvokeStatic(InvokeStatic node) {
-    addSideEffects(world.getSideEffectsOfElement(node.target));
-  }
-
-  void visitInvokeMethodDirectly(InvokeMethodDirectly node) {
-    FunctionElement target = node.target;
-    if (target is ConstructorBodyElement) {
-      ConstructorBodyElement body = target;
-      target = body.constructor;
-    }
-    addSideEffects(world.getSideEffectsOfElement(target));
-  }
-
-  void visitInvokeConstructor(InvokeConstructor node) {
-    addSideEffects(world.getSideEffectsOfElement(node.target));
-  }
-
-  void visitSetStatic(SetStatic node) {
-    currentLoopSideEffects.setChangesStaticProperty();
-  }
-
-  void visitGetStatic(GetStatic node) {
-    currentLoopSideEffects.setDependsOnStaticPropertyStore();
-  }
-
-  void visitGetField(GetField node) {
-    currentLoopSideEffects.setDependsOnInstancePropertyStore();
-  }
-
-  void visitSetField(SetField node) {
-    currentLoopSideEffects.setChangesInstanceProperty();
-  }
-
-  void visitGetIndex(GetIndex node) {
-    currentLoopSideEffects.setDependsOnIndexStore();
-  }
-
-  void visitSetIndex(SetIndex node) {
-    // Set the change index flag without setting the change length flag.
-    currentLoopSideEffects.setChangesIndex();
-  }
-
-  void visitForeignCode(ForeignCode node) {
-    addSideEffects(node.nativeBehavior.sideEffects);
-  }
-
-  void visitGetLazyStatic(GetLazyStatic node) {
-    // TODO(asgerf): How do we get the side effects of a lazy field initializer?
-    addAllSideEffects();
-  }
-
-  void visitAwait(Await node) {
-    addAllSideEffects();
-  }
-
-  void visitYield(Yield node) {
-    addAllSideEffects();
-  }
-
-  void visitApplyBuiltinMethod(ApplyBuiltinMethod node) {
-    currentLoopSideEffects.setChangesIndex();
-    currentLoopChangesLength = true; // Push and pop.
-  }
 }