Free names of inputs of an instruction that is generate at use site. An input of an instruction tha…

sdk/lib/_internal/compiler/implementation/ssa/variable_allocator.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;
 
 /**
  * The [LiveRange] class covers a range where an instruction is live.
  */
 class LiveRange {
@@ skipping 608 matching lines @@
   /**
    * Returns whether [instruction] dies at the instruction [at].
    */
   bool diesAt(HInstruction instruction, HInstruction at) {
     LiveInterval atInterval = liveIntervals[at];
     LiveInterval instructionInterval = liveIntervals[instruction];
     int start = atInterval.start;
     return instructionInterval.diesAt(start);
   }
 
-  void handleInstruction(HInstruction instruction, VariableNamer namer) {
+  void freeUsedNamesAt(HInstruction instruction,
+                       HInstruction at,
+                       VariableNamer namer) {
     // TODO(ager): We cannot perform this check to free names for
     // HCheck instructions because they are special cased to have the
     // same live intervals as the instruction they are checking. This
     // includes sharing the start id with the checked
     // input. Therefore, for HCheck(checkedInput, otherInput) we would
     // end up checking that otherInput dies not here, but at the
     // location of checkedInput. We should preserve the start id for
     // the check instruction.
-    if (instruction is! HCheck) {
+    if (at is HCheck) return;
+    if (needsName(instruction)) {
+      if (diesAt(instruction, at)) {
+        namer.freeName(instruction);
+      }
+    } else if (generateAtUseSite.contains(instruction)) {
+      // If the instruction is generated at use site, then all its
+      // inputs may also die at [at].
       for (int i = 0, len = instruction.inputs.length; i < len; i++) {
         HInstruction input = instruction.inputs[i];
-        // If [input] has a name, and its use here is the last use, free
-        // its name.
-        if (needsName(input) && diesAt(input, instruction)) {
-          namer.freeName(input);
-        }
+        freeUsedNamesAt(input, at, namer);
       }
     }
+  }
+
+  void handleInstruction(HInstruction instruction, VariableNamer namer) {
+    for (int i = 0, len = instruction.inputs.length; i < len; i++) {
+      HInstruction input = instruction.inputs[i];
+      freeUsedNamesAt(input, instruction, namer);
+    }
 
     if (needsName(instruction)) {
       namer.allocateName(instruction);
     }
   }
 
   void handlePhi(HPhi phi, VariableNamer namer) {
     if (!needsName(phi)) return;
 
     for (int i = 0; i < phi.inputs.length; i++) {
       HInstruction input = phi.inputs[i];
       HBasicBlock predecessor = phi.block.predecessors[i];
       if (!needsName(input)) {
         names.addAssignment(predecessor, input, phi);
       } else {
         names.addCopy(predecessor, input, phi);
       }
     }
 
     namer.allocateName(phi);
   }
 }