Reland of "[Turbofan] Fix perf regression (patchset #1 id:1 of https://codereview.chromium.org/14121

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 33 matching lines @@
     if (range->MayRequireSpillRange()) {
       data->CreateSpillRangeForLiveRange(range);
     }
     if (range->splinter() == nullptr) {
       TopLevelLiveRange *splinter = data->NextLiveRange(range->machine_type());
       DCHECK_NULL(data->live_ranges()[splinter->vreg()]);
       data->live_ranges()[splinter->vreg()] = splinter;
       range->SetSplinter(splinter);
     }
     Zone *zone = data->allocation_zone();
+    TRACE("creating splinter for range %d between %d and %d\n", range->vreg(),
+          start.ToInstructionIndex(), end.ToInstructionIndex());
     range->Splinter(start, end, zone);
   }
 }
 
 
 int FirstInstruction(const UseInterval *interval) {
   LifetimePosition start = interval->start();
   int ret = start.ToInstructionIndex();
   if (start.IsInstructionPosition() && start.IsEnd()) {
     ++ret;
@@ skipping 41 matching lines @@
         if (first_cut.IsValid()) {
           CreateSplinter(range, data, first_cut, last_cut);
           first_cut = LifetimePosition::Invalid();
           last_cut = LifetimePosition::Invalid();
         }
       }
     }
     interval = next_interval;
   }
   // When the range ends in deferred blocks, first_cut will be valid here.
+  // Splinter from there to the last instruction that was in a deferred block.
   if (first_cut.IsValid()) {
-    CreateSplinter(range, data, first_cut, range->End());
+    CreateSplinter(range, data, first_cut, last_cut);
   }
 }
 }  // namespace
 
 
 void LiveRangeSeparator::Splinter() {
   size_t virt_reg_count = data()->live_ranges().size();
   for (size_t vreg = 0; vreg < virt_reg_count; ++vreg) {
     TopLevelLiveRange *range = data()->live_ranges()[vreg];
     if (range == nullptr || range->IsEmpty() || range->IsSplinter()) {
@@ skipping 16 matching lines @@
     int to_remove = range->vreg();
     splinter_parent->Merge(range, data()->allocation_zone());
     data()->live_ranges()[to_remove] = nullptr;
   }
 }
 
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8