Remove restriction when computing instructions that can be generate at use site.

lib/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.
 
 /**
  * Instead of emitting each SSA instruction with a temporary variable
  * mark instructions that can be emitted at their use-site.
  * For example, in:
  *   t0 = 4;
  *   t1 = 3;
@@ skipping 74 matching lines @@
     // Keep a list of expected inputs of the current "expression" being
     // merged. If instructions occur in the expected order, they are
     // included in the expression.
 
     // The expectedInputs list holds non-trivial instructions that may
     // be generated at their use site, if they occur in the correct order.
     if (expectedInputs === null) expectedInputs = new List<HInstruction>();
 
     // Pop instructions from expectedInputs until instruction is found.
     // Return true if it is found, or false if not.
-    bool findInInputs(HInstruction instruction) {
+    bool findInInputsAndPopNonMatching(HInstruction instruction) {
       while (!expectedInputs.isEmpty()) {
         HInstruction nextInput = expectedInputs.removeLast();
         assert(!generateAtUseSite.contains(nextInput));
         assert(nextInput.usedBy.length == 1);
         if (nextInput === instruction) {
           return true;
         }
       }
       return false;
     }
@@ skipping 21 matching lines @@
     for (HInstruction instruction = block.last.previous;
          instruction !== null;
          instruction = instruction.previous) {
       if (generateAtUseSite.contains(instruction)) {
         continue;
       }
       if (instruction.isCodeMotionInvariant()) {
         generateAtUseSite.add(instruction);
         continue;
       }
-      bool foundInInputs = false;
       // See if the current instruction is the next non-trivial
-      // expected input. If not, drop the expectedInputs and
-      // start over.
-      if (findInInputs(instruction)) {
-        foundInInputs = true;
+      // expected input.
+      if (findInInputsAndPopNonMatching(instruction)) {
         tryGenerateAtUseSite(instruction);
       } else {
         assert(expectedInputs.isEmpty());
       }
-      if (foundInInputs || usedOnlyByPhis(instruction)) {
-        // Try merging all non-trivial inputs.
-        instruction.accept(this);
-      }
+      instruction.accept(this);
     }
 
     if (block.predecessors.length === 1
         && isBlockSinglePredecessor(block.predecessors[0])) {
       assert(block.phis.isEmpty());
       tryMergingExpressions(block.predecessors[0]);
     } else {
       expectedInputs = null;
     }
   }
@@ skipping 270 matching lines @@
     // improving the performance of future lookups.
     T root = getRepresentative(parent);
     if (root !== parent) representative[element] = root;
     return root;
   }
 
   bool areEquivalent(T a, T b) {
     return getRepresentative(a) === getRepresentative(b);
   }
 }