Small cleanups in RegExp to avoid generating lots of code just because there is a try/catch in our …

sdk/lib/_internal/compiler/implementation/ssa/optimize.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.
 
 part of ssa;
 
 abstract class OptimizationPhase {
   String get name;
   void visitGraph(HGraph graph);
 }
@@ skipping 120 matching lines @@
   visitBasicBlock(HBasicBlock block) {
     HInstruction instruction = block.first;
     while (instruction != null) {
       HInstruction next = instruction.next;
       HInstruction replacement = instruction.accept(this);
       if (replacement != instruction) {
         block.rewrite(instruction, replacement);
 
         // If we can replace [instruction] with [replacement], then
         // [replacement]'s type can be narrowed.
-        replacement.instructionType = replacement.instructionType.intersection(
+        HType newType = replacement.instructionType.intersection(
             instruction.instructionType, compiler);
+        if (!newType.isConflicting()) {
+          // [HType.intersection] may give up when doing the
+          // intersection of two types is too complicated, and return
+          // [HType.CONFLICTING]. We do not want instructions to have
+          // [HType.CONFLICTING], so we only update the type if the
+          // intersection did not give up.
+          replacement.instructionType = newType;
+        }
 
         // If the replacement instruction does not know its
         // source element, use the source element of the
         // instruction.
         if (replacement.sourceElement == null) {
           replacement.sourceElement = instruction.sourceElement;
         }
         if (replacement.sourcePosition == null) {
           replacement.sourcePosition = instruction.sourcePosition;
         }
@@ skipping 1373 matching lines @@
     HBasicBlock block = user.block;
     block.addAfter(user, interceptor);
     block.rewrite(user, interceptor);
     block.remove(user);
 
     // The interceptor will be removed in the dead code elimination
     // phase. Note that removing it here would not work because of how
     // the [visitBasicBlock] is implemented.
   }
 }