Avoid merging conditions across loop boundary

pkg/compiler/lib/src/ssa/codegen_helpers.dart

Index: pkg/compiler/lib/src/ssa/codegen_helpers.dart
diff --git a/pkg/compiler/lib/src/ssa/codegen_helpers.dart b/pkg/compiler/lib/src/ssa/codegen_helpers.dart
index eda5485a70c8697b6bd64377fd949b59c64bb9d4..43515f8ddc84a5af5f597208127cd7812bafa174 100644
--- a/pkg/compiler/lib/src/ssa/codegen_helpers.dart
+++ b/pkg/compiler/lib/src/ssa/codegen_helpers.dart
@@ -681,7 +681,8 @@ class SsaConditionMerger extends HGraphVisitor {
     // A [HIs] instruction uses its input multiple times, so we
     // avoid generating it at use site.
     if (user is HIs) return false;
-    return true;
+    // Avoid code motion into a loop.
+    return user.hasSameLoopHeaderAs(input);
   }
 
   void visitBasicBlock(HBasicBlock block) {