Lazy implementation of final variables.

lib/compiler/implementation/ssa/builder.dart

Index: lib/compiler/implementation/ssa/builder.dart
diff --git a/lib/compiler/implementation/ssa/builder.dart b/lib/compiler/implementation/ssa/builder.dart
index 941cbbb59f6e0a97536267ef8efdb9173040c870..610f9a4fc4088155d95c26ab6da20b4db0d45ec3 100644
--- a/lib/compiler/implementation/ssa/builder.dart
+++ b/lib/compiler/implementation/ssa/builder.dart
@@ -153,7 +153,7 @@ class SsaBuilderTask extends CompilerTask {
 
   HGraph build(WorkItem work) {
     return measure(() {
-      FunctionElement element = work.element;
+      Element element = work.element;
       HInstruction.idCounter = 0;
       SsaBuilder builder = new SsaBuilder(this, work);
       HGraph graph;
@@ -165,26 +165,32 @@ class SsaBuilderTask extends CompilerTask {
                  kind === ElementKind.GETTER ||
                  kind === ElementKind.SETTER) {
         graph = builder.buildMethod(work.element);
+      } else if (kind === ElementKind.FIELD) {
+        graph = builder.buildLazyInitializer(work.element);
       }
       assert(graph.isValid());
-      bool inLoop = functionsCalledInLoop.contains(element);
-      if (!inLoop) {
-        Selector selector = selectorsCalledInLoop[element.name];
-        inLoop = selector !== null && selector.applies(element, compiler);
-      }
-      graph.calledInLoop = inLoop;
-
-      // If there is an estimate of the parameter types assume these types when
-      // compiling.
-      List<HType> parameterTypes =
-          backend.optimisticParameterTypesWithRecompilationOnTypeChange(
-              element);
-      if (parameterTypes != null) {
-        FunctionSignature signature = element.computeSignature(compiler);
-        int i = 0;
-        signature.forEachParameter((Element param) {
-          builder.parameters[param].guaranteedType = parameterTypes[i++];
-        });
+      if (kind !== ElementKind.FIELD) {
+        bool inLoop = functionsCalledInLoop.contains(element);
+        if (!inLoop) {
+          Selector selector = selectorsCalledInLoop[element.name];
+          inLoop = selector !== null && selector.applies(element, compiler);
+        }
+        graph.calledInLoop = inLoop;
+
+        // If there is an estimate of the parameter types assume these types
+        // when compiling.
+        List<HType> parameterTypes =
+            backend.optimisticParameterTypesWithRecompilationOnTypeChange(
+                element);
+        if (parameterTypes != null) {
+          FunctionElement functionElement = element;
+          FunctionSignature signature =
+              functionElement.computeSignature(compiler);
+          int i = 0;
+          signature.forEachParameter((Element param) {
+            builder.parameters[param].guaranteedType = parameterTypes[i++];
+          });
+        }
       }
 
       if (compiler.tracer.enabled) {
@@ -860,6 +866,20 @@ class SsaBuilder extends ResolvedVisitor implements Visitor {
     return closeFunction();
   }
 
+  HGraph buildLazyInitializer(VariableElement variable) {
+    HBasicBlock block = graph.addNewBlock();
+    open(graph.entry);
+    close(new HGoto()).addSuccessor(block);
+    open(block);
+    SendSet node = variable.parseNode(compiler);
+    Link<Node> link = node.arguments;
+    assert(!link.isEmpty() && link.tail.isEmpty());
+    visit(link.head);
+    close(new HReturn(pop())).addSuccessor(graph.exit);
+    graph.finalize();
+    return graph;
+  }
+
   /**
    * Returns the constructor body associated with the given constructor or
    * creates a new constructor body, if none can be found.
@@ -1051,7 +1071,7 @@ class SsaBuilder extends ResolvedVisitor implements Visitor {
       if (value === null) {
         // The field has no value in the initializer list. Initialize it
         // with the declaration-site constant (if any).
-        Constant fieldValue = compiler.constantHandler.compileVariable(member);
+        Constant fieldValue = compiler.compileConstant(member);
         value = graph.addConstant(fieldValue);
       }
       constructorArguments.add(value);
@@ -1768,10 +1788,18 @@ class SsaBuilder extends ResolvedVisitor implements Visitor {
 
   void generateGetter(Send send, Element element) {
     if (Elements.isStaticOrTopLevelField(element)) {
+      Constant value;
       if (element.kind == ElementKind.FIELD && !element.isAssignable()) {

[kasperl, 2012/08/16 14:41:37]

isField?

[floitsch, 2012/08/16 22:52:33]

Done.

-        // A static final. Get its constant value and inline it.
-        Constant value = compiler.constantHandler.compileVariable(element);
+        // A static final or const. Get its constant value and inline it if
+        // the value can be compiled eagerly.
+        value = compiler.compileVariable(element);
+      }
+      if (value != null) {
         stack.add(graph.addConstant(value));
+      } else if (element.kind == ElementKind.FIELD &&
+                 compiler.isLazilyInitialized(element)) {
+        assert(element.kind == ElementKind.FIELD);

[kasperl, 2012/08/16 14:41:37]

Seems like a completely trivial assert given the condition.

[floitsch, 2012/08/16 22:52:33]

Done.

+        push(new HLazyStatic(element));
       } else {
         Selector selector = elements.getSelector(send);
         push(new HStatic(element));
@@ -1975,7 +2003,7 @@ class SsaBuilder extends ResolvedVisitor implements Visitor {
     }
 
     HInstruction compileConstant(Element constantElement) {
-      Constant constant = compiler.compileVariable(constantElement);
+      Constant constant = compiler.compileConstant(constantElement);
       return graph.addConstant(constant);
     }