[turbofan]: Elide extra move when accessing stack or frame register

src/compiler/instruction-selector-impl.h

 // 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.
 
 #ifndef V8_COMPILER_INSTRUCTION_SELECTOR_IMPL_H_
 #define V8_COMPILER_INSTRUCTION_SELECTOR_IMPL_H_
 
 #include "src/compiler/instruction.h"
 #include "src/compiler/instruction-selector.h"
 #include "src/compiler/linkage.h"
@@ skipping 57 matching lines @@
     sequence()->AddConstant(virtual_register, ToConstant(node));
     return ConstantOperand(virtual_register);
   }
 
   InstructionOperand DefineAsLocation(Node* node, LinkageLocation location,
                                       MachineType type) {
     return Define(node, ToUnallocatedOperand(location, type, GetVReg(node)));
   }
 
   InstructionOperand Use(Node* node) {
-    return Use(node, UnallocatedOperand(UnallocatedOperand::NONE,
-                                        UnallocatedOperand::USED_AT_START,
-                                        GetVReg(node)));
+    IrOpcode::Value opcode = node->opcode();
+    if (opcode == IrOpcode::kLoadFramePointer) {
+      return FramePointerOperand();
+    } else if (opcode == IrOpcode::kLoadStackPointer) {
+      return StackPointerOperand();
+    } else {
+      return Use(node, UnallocatedOperand(UnallocatedOperand::NONE,
+                                          UnallocatedOperand::USED_AT_START,
+                                          GetVReg(node)));
+    }
   }
 
   InstructionOperand UseRegister(Node* node) {
-    return Use(node, UnallocatedOperand(UnallocatedOperand::MUST_HAVE_REGISTER,
-                                        UnallocatedOperand::USED_AT_START,
-                                        GetVReg(node)));
+    IrOpcode::Value opcode = node->opcode();
+    if (opcode == IrOpcode::kLoadFramePointer) {
+      return FramePointerOperand();
+    } else if (opcode == IrOpcode::kLoadStackPointer) {
+      return StackPointerOperand();
+    } else {
+      return Use(node, UnallocatedOperand(
+                           UnallocatedOperand::MUST_HAVE_REGISTER,
+                           UnallocatedOperand::USED_AT_START, GetVReg(node)));
+    }
   }
 
   InstructionOperand UseUniqueSlot(Node* node) {
     return Use(node, UnallocatedOperand(UnallocatedOperand::MUST_HAVE_SLOT,
                                         GetVReg(node)));
   }
 
   // Use register or operand for the node. If a register is chosen, it won't
   // alias any temporary or output registers.
   InstructionOperand UseUnique(Node* node) {
@@ skipping 280 matching lines @@
                : (frame_state_descriptor->GetTotalSize() +
                   1);  // Include deopt id.
   }
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_INSTRUCTION_SELECTOR_IMPL_H_