Fix issue 10321 by invalidating previous "generate at use site" optimizations based on a pure instr…

sdk/lib/_internal/compiler/implementation/ssa/codegen_helpers.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;
 
 /**
  * Instead of emitting each SSA instruction with a temporary variable
  * mark instructions that can be emitted at their use-site.
  * For example, in:
@@ skipping 40 matching lines @@
           && !input.isJsStatement()) {
         if (input.isPure()) {
           // Only consider a pure input if it is in the same loop.
           // Otherwise, we might move GVN'ed instruction back into the
           // loop.
           if (user.hasSameLoopHeaderAs(input)) {
             // Move it closer to [user], so that instructions in
             // between do not prevent making it generate at use site.
             input.moveBefore(user);
             pureInputs.add(input);
+            // Previous computations done on [input] are now invalid
+            // because we moved [input] to another place. So all
+            // non code motion invariant instructions need
+            // to be removed from the [generateAtUseSite] set.
+            input.inputs.forEach((instruction) {
+              if (!instruction.isCodeMotionInvariant()) {
+                generateAtUseSite.remove(instruction);
+              }
+            });
             // Visit the pure input now so that the expected inputs
             // are after the expected inputs of [user].
             input.accept(this);
           }
         } else {
           expectedInputs.add(input);
         }
       }
     }
   }
@@ skipping 82 matching lines @@
         assert(!generateAtUseSite.contains(nextInput));
         assert(nextInput.usedBy.length == 1);
         if (identical(nextInput, instruction)) {
           return true;
         }
       }
       return false;
     }
 
     block.last.accept(this);
-    bool dontVisitPure = false;
     for (HInstruction instruction = block.last.previous;
          instruction != null;
          instruction = instruction.previous) {
       if (generateAtUseSite.contains(instruction)) {
         continue;
       }
       if (instruction.isCodeMotionInvariant()) {
         markAsGenerateAtUseSite(instruction);
         continue;
       }
@@ skipping 190 matching lines @@
     }
 
     // If [thenInput] is defined in the first predecessor, then it is only used
     // by [phi] and can be generated at use site.
     if (identical(thenInput.block, end.predecessors[0])) {
       assert(thenInput.usedBy.length == 1);
       markAsGenerateAtUseSite(thenInput);
     }
   }
 }