dart2js cps: Speed up integrity checking some more.

pkg/compiler/lib/src/js_backend/codegen/task.dart

Index: pkg/compiler/lib/src/js_backend/codegen/task.dart
diff --git a/pkg/compiler/lib/src/js_backend/codegen/task.dart b/pkg/compiler/lib/src/js_backend/codegen/task.dart
index 5942d14f9723c50fec8ead5f677827c43e714a08..7c0d3eae7641fe682c5607444c601a509f6d6c3b 100644
--- a/pkg/compiler/lib/src/js_backend/codegen/task.dart
+++ b/pkg/compiler/lib/src/js_backend/codegen/task.dart
@@ -102,6 +102,7 @@ class CpsFunctionCompiler implements FunctionCompiler {
         }
         cps.FunctionDefinition cpsFunction = compileToCpsIr(element);
         cpsFunction = optimizeCpsIr(cpsFunction);
+        cpsIntegrityChecker = null;
         tree_ir.FunctionDefinition treeFunction = compileToTreeIr(cpsFunction);
         treeFunction = optimizeTreeIr(treeFunction);
         return compileToJavaScript(work, treeFunction);
@@ -185,9 +186,14 @@ class CpsFunctionCompiler implements FunctionCompiler {
     }
   }
 
+  CheckCpsIntegrity cpsIntegrityChecker;
+
   bool checkCpsIntegrity(cps.FunctionDefinition node, String previousPass) {
     cpsOptimizationTask.measureSubtask('Check integrity', () {
-      new CheckCpsIntegrity().check(node, previousPass);
+      if (cpsIntegrityChecker == null) {

[sra1, 2015/10/15 23:06:52]

Is this worth it?

[asgerf, 2015/10/16 07:43:30]

It is necessary to ensure we get one instance per compiled method, and not one
instance per whole program or one per pass.

It would be cleaner to initialize it in the compile() method, but if we do it in
here, the class can be tree shaken and/or won't be parsed.

+        cpsIntegrityChecker = new CheckCpsIntegrity();
+      }
+      cpsIntegrityChecker.check(node, previousPass);
     });
     return true; // So this can be used from assert().
   }