[turbofan] Stand-alone deferred block splitting - full.

src/compiler/move-optimizer.cc

 // Copyright 2014 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/move-optimizer.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
@@ skipping 41 matching lines @@
       temp_vector_0_(local_zone),
       temp_vector_1_(local_zone) {}
 
 
 void MoveOptimizer::Run() {
   for (auto* block : code()->instruction_blocks()) {
     CompressBlock(block);
   }
   for (auto block : code()->instruction_blocks()) {
     if (block->PredecessorCount() <= 1) continue;
+    bool has_only_deferred = true;
+    for (RpoNumber pred_id : block->predecessors()) {
+      if (!code()->InstructionBlockAt(pred_id)->IsDeferred()) {
+        has_only_deferred = false;
+        break;
+      }
+    }
+    // This would pull down common moves. If the moves occur in deferred blocks,
+    // and the closest common successor is not deferred, we lose the
+    // optimization of just spilling/filling in deferred blocks.
+    if (has_only_deferred) continue;
     OptimizeMerge(block);
   }
   for (auto gap : to_finalize_) {
     FinalizeMoves(gap);
   }
 }
 
 
 void MoveOptimizer::CompressMoves(MoveOpVector* eliminated, ParallelMove* left,
                                   ParallelMove* right) {
@@ skipping 204 matching lines @@
         static_cast<Instruction::GapPosition>(1), code_zone());
     slot_1->AddMove(group_begin->destination(), load->destination());
     load->Eliminate();
   }
   loads.clear();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8