Merge libv1.

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 269 matching lines @@
     for (HPhi phi = block.phis.first; phi != null; phi = phi.next) {
       environment.remove(phi, instructionId);
     }
 
     // Save the liveInstructions of that block.
     environment.startId = instructionId + 1;
     liveInstructions[block] = environment;
 
     // If the block is a loop header, we can remove the loop marker,
     // because it will just recompute the loop phis.
-    if (block.isLoopHeader()) {
+    // We also check if this loop header has any back edges. If not,
+    // we know there is no loop marker for it.
+    if (block.isLoopHeader() && block.predecessors.length > 1) {
       updateLoopMarker(block);
     }
   }
 
   void updateLoopMarker(HBasicBlock header) {
     LiveEnvironment env = liveInstructions[header];
     int lastId = env.loopMarkers[header];
     // Update all instructions that are liveIns in [header] to have a
     // range that covers the loop.
     env.liveInstructions.forEach((HInstruction instruction, int id) {
@@ skipping 199 matching lines @@
     String name;
     if (instruction is HCheck) {
       // Special case this instruction to use the name of its
       // input if it has one.
       var temp = instruction;
       do {
         temp = temp.checkedInput;
         name = names.ownName[temp];
       } while (name == null && temp is HCheck);
       if (name != null) return addAllocatedName(instruction, name);
-    } else if (instruction is HParameterValue) {
-      HParameterValue parameter = instruction;
-      name = parameterNames[parameter.sourceElement];
-      if (name == null) {
-        name = allocateWithHint(parameter.sourceElement.name.slowToString());
-      }
-      return addAllocatedName(instruction, name);
     }
 
-    if (instruction.sourceElement != null) {
+    // The dom/html libraries have inline JS code that reference        
+    // parameter names directly. Long-term such code will be rejected.
+    // Now, just don't mangle the parameter name.
+    if (instruction is HParameterValue
+        && instruction.sourceElement.enclosingElement.isNative()) {
+      name = instruction.sourceElement.name.slowToString();
+    } else if (instruction.sourceElement != null) {
       name = allocateWithHint(instruction.sourceElement.name.slowToString());
     } else {
       // We could not find an element for the instruction. If the
       // instruction is used by a phi, try to use the name of the phi.
       // Otherwise, just allocate a temporary name.
       HPhi phi = firstPhiUserWithElement(instruction);
       if (phi != null) {
         name = allocateWithHint(phi.sourceElement.name.slowToString());
       } else {
         name = allocateTemporary();
       }
     }
 
     return addAllocatedName(instruction, name);
   }
 
   String addAllocatedName(HInstruction instruction, String name) {
+    if (instruction is HParameterValue) {
+      parameterNames[instruction.sourceElement] = name;
+    }
     usedNames.add(name);
     names.addNameUsed(name);
     names.ownName[instruction] = name;
     return name;
   }
 
   /**
    * Frees [instruction]'s name so it can be used for other instructions.
    */
   void freeName(HInstruction instruction) {
@@ skipping 57 matching lines @@
     block.forEachInstruction((HInstruction instruction) {
       handleInstruction(instruction, namer);
     });
   }
 
   /**
    * Returns whether [instruction] needs a name. Instructions that
    * have no users or that are generated at use site does not need a name.
    */
   bool needsName(HInstruction instruction) {
-    if (instruction.usedBy.isEmpty) return false;
     // TODO(ngeoffray): locals/parameters are being generated at use site,
     // but we need a name for them. We should probably not make
     // them generate at use site to make things simpler.
     if (instruction is HLocalValue && instruction is !HThis) return true;
+    if (instruction.usedBy.isEmpty) return false;
     if (generateAtUseSite.contains(instruction)) return false;
     // A [HCheck] instruction that has control flow needs a name only if its
     // checked input needs a name (e.g. a check [HConstant] does not
     // need a name).
     if (instruction is HCheck && instruction.isControlFlow()) {
       HCheck check = instruction;
       return needsName(instruction.checkedInput);
     }
     return true;
   }
@@ skipping 42 matching lines @@
       if (!needsName(input)) {
         names.addAssignment(predecessor, input, phi);
       } else {
         names.addCopy(predecessor, input, phi);
       }
     }
 
     namer.allocateName(phi);
   }
 }