[turbofan] Canonicalize return sequence for JSFunctions.

src/compiler/mips/code-generator-mips.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/code-generator.h"
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
 #include "src/mips/macro-assembler-mips.h"
 #include "src/scopes.h"
@@ skipping 1123 matching lines @@
       // Restore registers.
       const RegList saves = descriptor->CalleeSavedRegisters();
       if (saves != 0) {
         __ MultiPop(saves);
       }
     }
     __ mov(sp, fp);
     __ Pop(ra, fp);
     __ Ret();
   } else if (descriptor->IsJSFunctionCall() || needs_frame_) {
-    __ mov(sp, fp);
-    __ Pop(ra, fp);
-    int pop_count = descriptor->IsJSFunctionCall()
-                        ? static_cast<int>(descriptor->JSParameterCount())
-                        : 0;
-    __ DropAndRet(pop_count);
+    // Canonicalize JSFunction return sites for now.
+    if (return_label_.is_bound()) {
+      __ Branch(&return_label_);
+    } else {
+      __ bind(&return_label_);
+      __ mov(sp, fp);
+      __ Pop(ra, fp);
+      int pop_count = descriptor->IsJSFunctionCall()
+                          ? static_cast<int>(descriptor->JSParameterCount())
+                          : 0;
+      __ DropAndRet(pop_count);
+    }
   } else {
     __ Ret();
   }
 }
 
 
 void CodeGenerator::AssembleMove(InstructionOperand* source,
                                  InstructionOperand* destination) {
   MipsOperandConverter g(this, NULL);
   // Dispatch on the source and destination operand kinds.  Not all
@@ skipping 197 matching lines @@
       }
     }
   }
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8