[turbofan] LiveRange splitting at interval boundary fix.

src/compiler/register-allocator.cc

Index: src/compiler/register-allocator.cc
diff --git a/src/compiler/register-allocator.cc b/src/compiler/register-allocator.cc
index 28007d47fa11aadc60c0781e3793d76a13d39880..55023a200a4d9287c17f255c270de908667349cb 100644
--- a/src/compiler/register-allocator.cc
+++ b/src/compiler/register-allocator.cc
@@ -357,6 +357,8 @@ void LiveRange::SplitAt(LifetimePosition position, LiveRange* result,
     auto next = current->next();
     if (next->start() >= position) {
       split_at_start = (next->start() == position);
+      after = next;
+      current->set_next(nullptr);
       break;
     }
     current = next;
@@ -364,7 +366,6 @@ void LiveRange::SplitAt(LifetimePosition position, LiveRange* result,
 
   // Partition original use intervals to the two live ranges.
   auto before = current;
-  if (after == nullptr) after = before->next();
   result->last_interval_ =
       (last_interval_ == before)
           ? after            // Only interval in the range after split.