Reserve a state variable for the bailout function.

lib/compiler/implementation/ssa/codegen.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 class SsaCodeGeneratorTask extends CompilerTask {
 
   final JavaScriptBackend backend;
 
   SsaCodeGeneratorTask(JavaScriptBackend backend)
       : this.backend = backend,
@@ skipping 2678 matching lines @@
   }
 
   String popLabel() {
     return labels.removeLast();
   }
 
   String currentLabel() {
     return labels.last();
   }
 
+  js.VariableUse generateStateUse()
+      => new js.VariableUse(variableNames.stateName);
+
   HBasicBlock beginGraph(HGraph graph) {
     propagator = new SsaBailoutPropagator(compiler, generateAtUseSite);
     propagator.visitGraph(graph);
     // TODO(ngeoffray): We could avoid generating the state at the
     // call site for non-complex bailout methods.
-    newParameters.add(new js.Parameter('state'));
+    newParameters.add(new js.Parameter(variableNames.stateName));
 
     if (propagator.hasComplexBailoutTargets) {
       // Use generic parameters that will be assigned to
       // the right variables in the setup phase.
       for (int i = 0; i < propagator.maxBailoutParameters; i++) {
         String name = 'env$i';
         declaredVariables.add(name);
         newParameters.add(new js.Parameter(name));

[ngeoffray, 2012/10/15 14:12:29]

Something doesn't look right here: why do you need to do it for state but not
for env$i? Is it the declaredVariables.add call that makes it safe? Should you
do that for the state as well instead of this CL?

[floitsch, 2012/10/18 14:58:47]

There was still a bug in the handling of environment variables. But they are
easier to handle since they only live in the setup. The state variable is more
annoying since there are "state=0" statements sprinkled all over the function.
Even if state doesn't conflict with any argument it might still conflict with a
local. Therefore we have to reserve 'state' for the whole function.

Fix for env0... in https://codereview.chromium.org/11186048

       }
 
       startBailoutSwitch();
 
       // The setup phase of a bailout function sets up the environment for
       // each bailout target. Each bailout target will populate this
       // setup phase. It is put at the beginning of the function.
-      setup = new js.Switch(new js.VariableUse('state'), <js.SwitchClause>[]);
+      setup = new js.Switch(generateStateUse(), <js.SwitchClause>[]);
       return graph.entry;
     } else {
       // We have a simple bailout target, so we can reuse the names that
       // the bailout target expects.
       for (HInstruction input in propagator.firstBailoutTarget.inputs) {
         input = unwrap(input);
         String name = variableNames.getName(input);
         declaredVariables.add(name);
         newParameters.add(new js.Parameter(name));
       }
@@ skipping 50 matching lines @@
   }
 
   void visitBailoutTarget(HBailoutTarget node) {
     if (!propagator.hasComplexBailoutTargets) return;
 
     js.Block nextBlock = new js.Block.empty();
     js.Case clause = new js.Case(new js.LiteralNumber('${node.state}'),
                                  nextBlock);
     currentBailoutSwitch.cases.add(clause);
     currentContainer = nextBlock;
-    pushExpressionAsStatement(new js.Assignment(new js.VariableUse('state'),
+    pushExpressionAsStatement(new js.Assignment(generateStateUse(),
                                                 new js.LiteralNumber('0')));
     js.Block setupBlock = new js.Block.empty();
     int i = 0;
     for (HInstruction input in node.inputs) {
       input = unwrap(input);
       String name = variableNames.getName(input);
       if (!isVariableDeclared(name)) {
         declaredVariables.add(name);
         js.VariableInitialization init =
             new js.VariableInitialization(new js.VariableDeclaration(name),
@@ skipping 36 matching lines @@
       currentBailoutSwitch.cases.add(new js.Case(expr, new js.Block.empty()));
     }
   }
 
   void startBailoutSwitch() {
     defaultClauseUsedInBailoutStack.add(false);
     oldBailoutSwitches.add(currentBailoutSwitch);
     List<js.SwitchClause> cases = <js.SwitchClause>[];
     js.Block firstBlock = new js.Block.empty();
     cases.add(new js.Case(new js.LiteralNumber("0"), firstBlock));
-    currentBailoutSwitch = new js.Switch(new js.VariableUse('state'), cases);
+    currentBailoutSwitch = new js.Switch(generateStateUse(), cases);
     pushStatement(currentBailoutSwitch);
     oldContainerStack.add(currentContainer);
     currentContainer = firstBlock;
   }
 
   js.Switch endBailoutSwitch() {
     js.Switch result = currentBailoutSwitch;
     currentBailoutSwitch = oldBailoutSwitches.removeLast();
     defaultClauseUsedInBailoutStack.removeLast();
     currentContainer = oldContainerStack.removeLast();
@@ skipping 56 matching lines @@
     if (!hasGuards) {
       super.generateIf(node, info);
       return;
     }
 
     startBailoutCase(thenGraph.start.bailoutTargets,
                      elseGraph.start.bailoutTargets);
 
     use(node.inputs[0]);
     js.Binary stateEquals0 =
-        new js.Binary('===',
-                      new js.VariableUse('state'), new js.LiteralNumber('0'));
+        new js.Binary('===', generateStateUse(), new js.LiteralNumber('0'));
     js.Expression condition = new js.Binary('&&', stateEquals0, pop());
     // TODO(ngeoffray): Put the condition initialization in the
     // [setup] buffer.
     List<HBailoutTarget> targets = node.thenBlock.bailoutTargets;
     for (int i = 0, len = targets.length; i < len; i++) {
-      js.VariableUse stateRef = new js.VariableUse('state');
+      js.VariableUse stateRef = generateStateUse();
       js.Expression targetState = new js.LiteralNumber('${targets[i].state}');
       js.Binary stateTest = new js.Binary('===', stateRef, targetState);
       condition = new js.Binary('||', stateTest, condition);
     }
 
     js.Statement thenBody = new js.Block.empty();
     js.Block oldContainer = currentContainer;
     currentContainer = thenBody;
     if (thenHasGuards) startBailoutSwitch();
     generateStatements(thenGraph);
@@ skipping 45 matching lines @@
   if (leftType.canBeNull() && rightType.canBeNull()) {
     if (left.isConstantNull() || right.isConstantNull() ||
         (leftType.isPrimitive() && leftType == rightType)) {
       return '==';
     }
     return null;
   } else {
     return '===';
   }
 }