Add a MathFloor stub generated with TurboFan

src/compiler/linkage.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/code-stubs.h"
 #include "src/compiler.h"
 #include "src/compiler/linkage.h"
 #include "src/compiler/node.h"
 #include "src/compiler/pipeline.h"
 #include "src/scopes.h"
@@ skipping 33 matching lines @@
   for (size_t i = 0; i < ReturnCount(); ++i) {
     if (GetReturnLocation(i) != other->GetReturnLocation(i)) return false;
   }
   return true;
 }
 
 
 CallDescriptor* Linkage::ComputeIncoming(Zone* zone, CompilationInfo* info) {
   if (info->code_stub() != NULL) {
     // Use the code stub interface descriptor.
-    CallInterfaceDescriptor descriptor =
-        info->code_stub()->GetCallInterfaceDescriptor();
-    return GetStubCallDescriptor(info->isolate(), zone, descriptor, 0,
-                                 CallDescriptor::kNoFlags,
-                                 Operator::kNoProperties);
+    CodeStub* stub = info->code_stub();
+    CallInterfaceDescriptor descriptor = stub->GetCallInterfaceDescriptor();
+    return GetStubCallDescriptor(
+        info->isolate(), zone, descriptor, stub->GetStackParameterCount(),
+        CallDescriptor::kNoFlags, Operator::kNoProperties);
   }
   if (info->function() != NULL) {
     // If we already have the function literal, use the number of parameters
     // plus the receiver.
     return GetJSCallDescriptor(zone, info->is_osr(),
                                1 + info->function()->parameter_count(),
                                CallDescriptor::kNoFlags);
   }
   if (!info->closure().is_null()) {
     // If we are compiling a JS function, use a JS call descriptor,
@@ skipping 130 matching lines @@
 
 CallDescriptor* Linkage::GetSimplifiedCDescriptor(Zone* zone,
                                                   const MachineSignature* sig) {
   UNIMPLEMENTED();
   return NULL;
 }
 #endif  // !V8_TURBOFAN_BACKEND
 }
 }
 }  // namespace v8::internal::compiler