Restore WritableRegister input LiveRange shape

runtime/vm/flow_graph_allocator.cc

 // Copyright (c) 2013, 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.
 
 #include "vm/flow_graph_allocator.h"
 
 #include "vm/bit_vector.h"
 #include "vm/intermediate_language.h"
 #include "vm/il_printer.h"
 #include "vm/flow_graph.h"
@@ skipping 895 matching lines @@
     MoveOperands* move =
         AddMoveAt(pos - 1, *in_ref, Location::Any());
     BlockLocation(*in_ref, pos - 1, pos + 1);
     range->AddUseInterval(block->start_pos(), pos - 1);
     range->AddHintedUse(pos - 1, move->src_slot(), in_ref);
   } else if (in_ref->IsUnallocated()) {
     if (in_ref->policy() == Location::kWritableRegister) {
       // Writable unallocated input. Expected shape of
       // live ranges:
       //
-      //                 j' i  i'
+      //                 i  i'
       //      value    --*
-      //      temp       [------)
-      MoveOperands* move = AddMoveAt(pos - 1,
+      //      temp       [--)
+      MoveOperands* move = AddMoveAt(pos,
                                      Location::RequiresRegister(),
                                      Location::PrefersRegister());
 
       // Add uses to the live range of the input.
-      range->AddUseInterval(block->start_pos(), pos - 1);
-      range->AddUse(pos - 1, move->src_slot());
+      range->AddUseInterval(block->start_pos(), pos);
+      range->AddUse(pos, move->src_slot());
 
       // Create live range for the temporary.
       LiveRange* temp = MakeLiveRangeForTemporary();
-      temp->AddUseInterval(pos - 1, pos + 1);
-      temp->AddHintedUse(pos - 1, in_ref, move->src_slot());
-      temp->AddUse(pos + 1, move->dest_slot());
+      temp->AddUseInterval(pos, pos + 1);
+      temp->AddHintedUse(pos, in_ref, move->src_slot());
+      temp->AddUse(pos, move->dest_slot());
       *in_ref = Location::RequiresRegister();
       CompleteRange(temp, RegisterKindFromPolicy(*in_ref));
     } else {
       // Normal unallocated input. Expected shape of
       // live ranges:
       //
       //                 i  i'
       //      value    -----*
       //
       range->AddUseInterval(block->start_pos(), pos + 1);
@@ skipping 1839 matching lines @@
     OS::Print("-- [after ssa allocator] ir [%s] -------------\n",
               function.ToFullyQualifiedCString());
     FlowGraphPrinter printer(flow_graph_, true);
     printer.PrintBlocks();
     OS::Print("----------------------------------------------\n");
   }
 }
 
 
 }  // namespace dart