Prevent hoisting of certain check nodes, including [HTypeKnown].

sdk/lib/_internal/compiler/implementation/ssa/optimize.dart

Index: sdk/lib/_internal/compiler/implementation/ssa/optimize.dart
diff --git a/sdk/lib/_internal/compiler/implementation/ssa/optimize.dart b/sdk/lib/_internal/compiler/implementation/ssa/optimize.dart
index b5757726f6a670514de7a9b3c6baa4368aafa454..2957676c99fabc99062e6b000c32821ff4046837 100644
--- a/sdk/lib/_internal/compiler/implementation/ssa/optimize.dart
+++ b/sdk/lib/_internal/compiler/implementation/ssa/optimize.dart
@@ -1243,7 +1243,7 @@ class SsaGlobalValueNumberer implements OptimizationPhase {
             && loopHeader.successors[0] == block);
     while (instruction != null) {
       HInstruction next = instruction.next;
-      if (instruction.useGvn()
+      if (instruction.useGvn() && instruction.isMovable
           && (!instruction.canThrow() || firstInstructionInLoop)
           && !instruction.sideEffects.dependsOn(dependsFlags)) {
         bool loopInvariantInputs = true;
@@ -1465,11 +1465,7 @@ class SsaCodeMotion extends HBaseVisitor implements OptimizationPhase {
 
       HInstruction current = instruction;
       instruction = instruction.next;
-
-      // TODO(ngeoffray): this check is needed because we currently do
-      // not have flags to express 'Gvn'able', but not movable.
-      if (current is HCheck) continue;
-      if (!current.useGvn()) continue;
+      if (!current.useGvn() || !current.isMovable) continue;
       if (current.sideEffects.dependsOn(dependsFlags)) continue;
 
       bool canBeMoved = true;
@@ -1504,14 +1500,15 @@ class SsaTypeConversionInserter extends HBaseVisitor
   }
 
   // Update users of [input] that are dominated by [:dominator.first:]
-  // to use [newInput] instead.
+  // to use [newInput] instead. As the type information depends on the
+  // control flow, we mark the inserted [HTypeKnown] nodes as non-movable.
   void changeUsesDominatedBy(HBasicBlock dominator,

[floitsch, 2014/03/20 16:07:25]

Nit: we should change the name. It's not just changing the users. It's also
inserting an HTypeKnown node.

[herhut, 2014/03/20 16:25:11]

It is now called [insertTypePropagationForDominatedUsers]

Done.

                              HInstruction input,
                              TypeMask convertedType) {
     Setlet<HInstruction> dominatedUsers = input.dominatedUsers(dominator.first);
     if (dominatedUsers.isEmpty) return;
 
-    HTypeKnown newInput = new HTypeKnown(convertedType, input);
+    HTypeKnown newInput = new HTypeKnown.pinned(convertedType, input);
     dominator.addBefore(dominator.first, newInput);
     dominatedUsers.forEach((HInstruction user) {
       user.changeUse(input, newInput);