[turbofan] Canonicalize return sequence for JSFunctions.

src/compiler/x64/code-generator-x64.cc

 // Copyright 2013 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/code-generator.h"
 
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
 #include "src/scopes.h"
@@ skipping 1520 matching lines @@
       }
       __ popq(rbp);  // Pop caller's frame pointer.
       __ ret(0);
     } else {
       // No saved registers.
       __ movq(rsp, rbp);  // Move stack pointer back to frame pointer.
       __ popq(rbp);       // Pop caller's frame pointer.
       __ ret(0);
     }
   } else if (descriptor->IsJSFunctionCall() || needs_frame_) {
-    __ movq(rsp, rbp);  // Move stack pointer back to frame pointer.
-    __ popq(rbp);       // Pop caller's frame pointer.
-    int pop_count = descriptor->IsJSFunctionCall()
-                        ? static_cast<int>(descriptor->JSParameterCount())
-                        : 0;
-    __ Ret(pop_count * kPointerSize, rbx);
+    // Canonicalize JSFunction return sites for now.
+    if (return_label_.is_bound()) {
+      __ jmp(&return_label_);
+    } else {
+      __ bind(&return_label_);
+      __ movq(rsp, rbp);  // Move stack pointer back to frame pointer.
+      __ popq(rbp);       // Pop caller's frame pointer.
+      int pop_count = descriptor->IsJSFunctionCall()
+                          ? static_cast<int>(descriptor->JSParameterCount())
+                          : 0;
+      __ Ret(pop_count * kPointerSize, rbx);
+    }
   } else {
     __ ret(0);
   }
 }
 
 
 void CodeGenerator::AssembleMove(InstructionOperand* source,
                                  InstructionOperand* destination) {
   X64OperandConverter g(this, NULL);
   // Dispatch on the source and destination operand kinds.  Not all
@@ skipping 180 matching lines @@
       __ Nop(padding_size);
     }
   }
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace compiler
 }  // namespace v8