dart2js cps: Streamline expressions and primitives.

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

Index: pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
diff --git a/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart b/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
index 37e91fe15c09214d1a826163661a57e93dcd4d6c..31c14680f471540da06cb5d3dbe83ece3bf7da61 100644
--- a/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
+++ b/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
@@ -64,7 +64,11 @@ abstract class InteriorNode extends Node {
   void set body(Expression body);
 }
 
-/// An expression with a subexpression as body.
+/// An expression that creates new bindings and continues evaluation in
+/// a subexpression.
+/// 
+/// The interior expressions are [LetPrim], [LetCont], [LetHandler], and
+/// [LetMutable].
 abstract class InteriorExpression extends Expression implements InteriorNode {
   Expression get next => body;
 }
@@ -557,17 +561,17 @@ class Unreachable extends TailExpression {
 /// Gets the value from a [MutableVariable].
 ///
 /// [MutableVariable]s can be seen as ref cells that are not first-class
-/// values.  A [LetPrim] with a [GetMutableVariable] can then be seen as:
+/// values.  A [LetPrim] with a [GetMutable] can then be seen as:
 ///
 ///   let prim p = ![variable] in [body]
 ///
-class GetMutableVariable extends Primitive {
+class GetMutable extends Primitive {
   final Reference<MutableVariable> variable;
 
-  GetMutableVariable(MutableVariable variable)
+  GetMutable(MutableVariable variable)
       : this.variable = new Reference<MutableVariable>(variable);
 
-  accept(Visitor visitor) => visitor.visitGetMutableVariable(this);
+  accept(Visitor visitor) => visitor.visitGetMutable(this);
 
   bool get isSafeForElimination => true;
   bool get isSafeForReordering => false;
@@ -579,21 +583,18 @@ class GetMutableVariable extends Primitive {
 /// values.  This can be seen as a dereferencing assignment:
 ///
 ///   { [variable] := [value]; [body] }
-class SetMutableVariable extends InteriorExpression {
+class SetMutable extends Primitive {
   final Reference<MutableVariable> variable;
   final Reference<Primitive> value;
-  Expression body;
 
-  SetMutableVariable(MutableVariable variable, Primitive value)
+  SetMutable(MutableVariable variable, Primitive value)
       : this.variable = new Reference<MutableVariable>(variable),
         this.value = new Reference<Primitive>(value);
 
-  accept(Visitor visitor) => visitor.visitSetMutableVariable(this);
+  accept(Visitor visitor) => visitor.visitSetMutable(this);
 
-  Expression plug(Expression expr) {
-    assert(body == null);
-    return body = expr;
-  }
+  bool get isSafeForElimination => false;
+  bool get isSafeForReordering => false;
 }
 
 /// Invoke a continuation in tail position.
@@ -662,22 +663,19 @@ class Branch extends TailExpression {
 }
 
 /// Directly assigns to a field on a given object.
-class SetField extends InteriorExpression {
+class SetField extends Primitive {
   final Reference<Primitive> object;
   FieldElement field;
   final Reference<Primitive> value;
-  Expression body;
 
   SetField(Primitive object, this.field, Primitive value)
       : this.object = new Reference<Primitive>(object),
         this.value = new Reference<Primitive>(value);
 
-  Expression plug(Expression expr) {
-    assert(body == null);
-    return body = expr;
-  }
-
   accept(Visitor visitor) => visitor.visitSetField(this);
+  
+  bool get isSafeForElimination => false;
+  bool get isSafeForReordering => false;
 }
 
 /// Directly reads from a field on a given object.
@@ -778,21 +776,18 @@ class GetStatic extends Primitive {
 }
 
 /// Sets the value of a static field.
-class SetStatic extends InteriorExpression {
+class SetStatic extends Primitive {
   final FieldElement element;
   final Reference<Primitive> value;
-  Expression body;
   final SourceInformation sourceInformation;
 
   SetStatic(this.element, Primitive value, [this.sourceInformation])
       : this.value = new Reference<Primitive>(value);
 
-  Expression plug(Expression expr) {
-    assert(body == null);
-    return body = expr;
-  }
-
   accept(Visitor visitor) => visitor.visitSetStatic(this);
+
+  bool get isSafeForElimination => false;
+  bool get isSafeForReordering => false;
 }
 
 /// Reads the value of a lazily initialized static field.
@@ -1125,7 +1120,7 @@ abstract class Visitor<T> {
   T visitRethrow(Rethrow node);
   T visitBranch(Branch node);
   T visitTypeCast(TypeCast node);
-  T visitSetMutableVariable(SetMutableVariable node);
+  T visitSetMutable(SetMutable node);
   T visitSetStatic(SetStatic node);
   T visitGetLazyStatic(GetLazyStatic node);
   T visitSetField(SetField node);
@@ -1136,7 +1131,7 @@ abstract class Visitor<T> {
   T visitLiteralMap(LiteralMap node);
   T visitConstant(Constant node);
   T visitCreateFunction(CreateFunction node);
-  T visitGetMutableVariable(GetMutableVariable node);
+  T visitGetMutable(GetMutable node);
   T visitParameter(Parameter node);
   T visitContinuation(Continuation node);
   T visitMutableVariable(MutableVariable node);
@@ -1283,12 +1278,11 @@ class RecursiveVisitor implements Visitor {
     node.typeArguments.forEach(processReference);
   }
 
-  processSetMutableVariable(SetMutableVariable node) {}
-  visitSetMutableVariable(SetMutableVariable node) {
-    processSetMutableVariable(node);
+  processSetMutable(SetMutable node) {}
+  visitSetMutable(SetMutable node) {
+    processSetMutable(node);
     processReference(node.variable);
     processReference(node.value);
-    visit(node.body);
   }
 
   processGetLazyStatic(GetLazyStatic node) {}
@@ -1328,9 +1322,9 @@ class RecursiveVisitor implements Visitor {
     processMutableVariable(node);
   }
 
-  processGetMutableVariable(GetMutableVariable node) {}
-  visitGetMutableVariable(GetMutableVariable node) {
-    processGetMutableVariable(node);
+  processGetMutable(GetMutable node) {}
+  visitGetMutable(GetMutable node) {
+    processGetMutable(node);
     processReference(node.variable);
   }
 
@@ -1370,7 +1364,6 @@ class RecursiveVisitor implements Visitor {
     processSetField(node);
     processReference(node.object);
     processReference(node.value);
-    visit(node.body);
   }
 
   processGetField(GetField node) {}
@@ -1388,7 +1381,6 @@ class RecursiveVisitor implements Visitor {
   visitSetStatic(SetStatic node) {
     processSetStatic(node);
     processReference(node.value);
-    visit(node.body);
   }
 
   processCreateBox(CreateBox node) {}