[turbofan] Remove the JSContextRelaxation reducer.

src/compiler/js-context-relaxation.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/frame-states.h"
-#include "src/compiler/js-context-relaxation.h"
-#include "src/compiler/js-operator.h"
-#include "src/compiler/node.h"
-#include "src/compiler/node-properties.h"
-
-namespace v8 {
-namespace internal {
-namespace compiler {
-
-Reduction JSContextRelaxation::Reduce(Node* node) {
-  switch (node->opcode()) {
-    case IrOpcode::kJSCallFunction:
-    case IrOpcode::kJSToNumber: {
-      Node* frame_state = NodeProperties::GetFrameStateInput(node, 0);
-      Node* outer_frame = frame_state;
-      Node* original_context = NodeProperties::GetContextInput(node);
-      Node* candidate_new_context = original_context;
-      do {
-        FrameStateInfo frame_state_info(
-            OpParameter<FrameStateInfo>(outer_frame->op()));
-        const FrameStateFunctionInfo* function_info =
-            frame_state_info.function_info();
-        if (function_info == nullptr ||
-            (function_info->context_calling_mode() ==
-             CALL_CHANGES_NATIVE_CONTEXT)) {
-          break;
-        }
-        candidate_new_context = outer_frame->InputAt(kFrameStateContextInput);
-        outer_frame = outer_frame->InputAt(kFrameStateOuterStateInput);
-      } while (outer_frame->opcode() == IrOpcode::kFrameState);
-
-      while (true) {
-        switch (candidate_new_context->opcode()) {
-          case IrOpcode::kParameter:
-          case IrOpcode::kJSCreateModuleContext:
-          case IrOpcode::kJSCreateScriptContext:
-            if (candidate_new_context != original_context) {
-              NodeProperties::ReplaceContextInput(node, candidate_new_context);
-              return Changed(node);
-            } else {
-              return NoChange();
-            }
-          case IrOpcode::kJSCreateCatchContext:
-          case IrOpcode::kJSCreateWithContext:
-          case IrOpcode::kJSCreateBlockContext:
-            candidate_new_context =
-                NodeProperties::GetContextInput(candidate_new_context);
-            break;
-          default:
-            return NoChange();
-        }
-      }
-    }
-    default:
-      break;
-  }
-  return NoChange();
-}
-
-}  // namespace compiler
-}  // namespace internal
-}  // namespace v8