X87: HydrogenCodeStubs consume stack arguments via descriptor.

src/x87/interface-descriptors-x87.cc

Index: src/x87/interface-descriptors-x87.cc
diff --git a/src/x87/interface-descriptors-x87.cc b/src/x87/interface-descriptors-x87.cc
index 333564e09995afffc834146186bd7a14b4567cf8..a71c269f860065bc310cea4bd6442b51e02fa08e 100644
--- a/src/x87/interface-descriptors-x87.cc
+++ b/src/x87/interface-descriptors-x87.cc
@@ -32,7 +32,9 @@ const Register VectorStoreICTrampolineDescriptor::SlotRegister() { return edi; }
 const Register VectorStoreICDescriptor::VectorRegister() { return ebx; }
 
 
-const Register StoreTransitionDescriptor::MapRegister() { return ebx; }
+const Register StoreTransitionDescriptor::MapRegister() {
+  return FLAG_vector_stores ? no_reg : ebx;
+}
 
 
 const Register LoadGlobalViaContextDescriptor::DepthRegister() { return edx; }
@@ -69,6 +71,20 @@ const Register GrowArrayElementsDescriptor::ObjectRegister() { return eax; }
 const Register GrowArrayElementsDescriptor::KeyRegister() { return ebx; }
 
 
+void StoreTransitionDescriptor::InitializePlatformSpecific(
+    CallInterfaceDescriptorData* data) {
+  Register registers[] = {ReceiverRegister(), NameRegister(), ValueRegister(),
+                          MapRegister()};
+
+  // When FLAG_vector_stores is true, we want to pass the map register on the
+  // stack instead of in a register.
+  DCHECK(FLAG_vector_stores || !MapRegister().is(no_reg));
+
+  int register_count = FLAG_vector_stores ? 3 : 4;
+  data->InitializePlatformSpecific(register_count, registers);
+}
+
+
 void FastNewClosureDescriptor::InitializePlatformSpecific(
     CallInterfaceDescriptorData* data) {
   Register registers[] = {ebx};