[turbofan] LiveRange splintering optimizations.

src/compiler/live-range-separator.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/live-range-separator.h"
 #include "src/compiler/register-allocator.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
@@ skipping 100 matching lines @@
   InstructionSequence *code = data->code();
   int code_block_count = code->InstructionBlockCount();
   Zone *zone = data->allocation_zone();
   ZoneVector<BitVector *> &in_sets = data->live_in_sets();
 
   for (int i = 0; i < code_block_count; ++i) {
     InstructionBlock *block = code->InstructionBlockAt(RpoNumber::FromInt(i));
     if (!block->IsDeferred()) continue;
 
     RpoNumber last_deferred = block->last_deferred();
-    i = last_deferred.ToInt();
+    // last_deferred + 1 is not deferred, so no point in visiting it.
+    i = last_deferred.ToInt() + 1;
 
     LifetimePosition first_cut = LifetimePosition::GapFromInstructionIndex(
         block->first_instruction_index());
 
     LifetimePosition last_cut = LifetimePosition::GapFromInstructionIndex(
         static_cast<int>(code->instructions().size()));
 
-    const BitVector *in_set = in_sets[i];
+    const BitVector *in_set = in_sets[block->rpo_number().ToInt()];
     InstructionBlock *last = code->InstructionBlockAt(last_deferred);
     const BitVector *out_set = LiveRangeBuilder::ComputeLiveOut(last, data);
     last_cut = LifetimePosition::GapFromInstructionIndex(
         last->last_instruction_index());
 
     BitVector ranges_to_splinter(*in_set, zone);
     ranges_to_splinter.Union(*out_set);
     BitVector::Iterator iterator(&ranges_to_splinter);
 
     while (!iterator.Done()) {
@@ skipping 24 matching lines @@
     TopLevelLiveRange *splinter_parent = range->splintered_from();
 
     splinter_parent->Merge(range, data());
   }
 }
 
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8