[turbofan] Emit explicit checkpoint before operations.

src/compiler/bytecode-graph-builder.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/bytecode-graph-builder.h"
 
 #include "src/compiler/bytecode-branch-analysis.h"
 #include "src/compiler/linkage.h"
 #include "src/compiler/operator-properties.h"
 #include "src/interpreter/bytecodes.h"
@@ skipping 91 matching lines @@
         id_after_(BailoutId::None()),
         added_to_node_(false),
         frame_states_unused_(false),
         output_poke_offset_(0),
         output_poke_count_(0) {
     BailoutId id_before(builder->bytecode_iterator().current_offset());
     frame_state_before_ = builder_->environment()->Checkpoint(
         id_before, OutputFrameStateCombine::Ignore());
     id_after_ = BailoutId(id_before.ToInt() +
                           builder->bytecode_iterator().current_bytecode_size());
+    // Create an explicit checkpoint node for before the operation.
+    Node* node = builder_->NewNode(builder_->common()->Checkpoint());
+    DCHECK_EQ(IrOpcode::kDead,
+              NodeProperties::GetFrameStateInput(node, 0)->opcode());
+    NodeProperties::ReplaceFrameStateInput(node, 0, frame_state_before_);
   }
 
   ~FrameStateBeforeAndAfter() {
     DCHECK(added_to_node_);
     DCHECK(frame_states_unused_ ||
            builder_->environment()->StateValuesAreUpToDate(output_poke_offset_,
                                                            output_poke_count_));
   }
 
  private:
   friend class Environment;
 
   void AddToNode(Node* node, OutputFrameStateCombine combine) {
     DCHECK(!added_to_node_);
     int count = OperatorProperties::GetFrameStateInputCount(node->op());
     DCHECK_LE(count, 2);
     if (count >= 1) {
       // Add the frame state for after the operation.
       DCHECK_EQ(IrOpcode::kDead,
                 NodeProperties::GetFrameStateInput(node, 0)->opcode());
       Node* frame_state_after =
           builder_->environment()->Checkpoint(id_after_, combine);
       NodeProperties::ReplaceFrameStateInput(node, 0, frame_state_after);
     }
 
     if (count >= 2) {
       // Add the frame state for before the operation.
+      // TODO(mstarzinger): Get rid of frame state input before!
       DCHECK_EQ(IrOpcode::kDead,
                 NodeProperties::GetFrameStateInput(node, 1)->opcode());
       NodeProperties::ReplaceFrameStateInput(node, 1, frame_state_before_);
     }
 
     if (!combine.IsOutputIgnored()) {
       output_poke_offset_ = static_cast<int>(combine.GetOffsetToPokeAt());
       output_poke_count_ = node->op()->ValueOutputCount();
     }
     frame_states_unused_ = count == 0;
@@ skipping 1574 matching lines @@
     // Phi does not exist yet, introduce one.
     value = NewPhi(inputs, value, control);
     value->ReplaceInput(inputs - 1, other);
   }
   return value;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8