[ia32] Unalias kRootRegister in LoadWithVector and LoadGlobalWithVector

In preparation for kRootRegister support on ia32.

LoadWithVector now passes the vector on the stack.
LoadGlobalWithVector is able to reuse edx (used as ReceiverRegister in
LoadWithVector).

Drive-by: Aliasing DCHECKs and updated unused Register accessors.

Bug: v8:6666
Change-Id: If0e93d22c3c11f764bc0805c3e6a51654cdcc5f9
Reviewed-on: https://chromium-review.googlesource.com/1193891
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55490}

src/ia32/interface-descriptors-ia32.cc

@@ -49,17 +49,17 @@ const Register LoadDescriptor::ReceiverRegister() { return edx; }
 const Register LoadDescriptor::NameRegister() { return ecx; }
 const Register LoadDescriptor::SlotRegister() { return eax; }
 
-const Register LoadWithVectorDescriptor::VectorRegister() { return ebx; }
+const Register LoadWithVectorDescriptor::VectorRegister() { return no_reg; }
 
 const Register StoreDescriptor::ReceiverRegister() { return edx; }
 const Register StoreDescriptor::NameRegister() { return ecx; }
-const Register StoreDescriptor::ValueRegister() { return eax; }
-const Register StoreDescriptor::SlotRegister() { return edi; }
+const Register StoreDescriptor::ValueRegister() { return no_reg; }
+const Register StoreDescriptor::SlotRegister() { return no_reg; }
 
-const Register StoreWithVectorDescriptor::VectorRegister() { return ebx; }
+const Register StoreWithVectorDescriptor::VectorRegister() { return no_reg; }
 
 const Register StoreTransitionDescriptor::SlotRegister() { return no_reg; }
-const Register StoreTransitionDescriptor::VectorRegister() { return ebx; }
+const Register StoreTransitionDescriptor::VectorRegister() { return no_reg; }
 const Register StoreTransitionDescriptor::MapRegister() { return edi; }
 
 const Register ApiGetterDescriptor::HolderRegister() { return ecx; }

src/interface-descriptors.cc

@@ -260,13 +260,21 @@ void LoadWithVectorDescriptor::InitializePlatformSpecific(
     CallInterfaceDescriptorData* data) {
   Register registers[] = {ReceiverRegister(), NameRegister(), SlotRegister(),
                           VectorRegister()};
-  data->InitializePlatformSpecific(arraysize(registers), registers);
+  // TODO(jgruber): This DCHECK could be enabled if RegisterBase::ListOf were
+  // to allow no_reg entries.
+  // DCHECK(!AreAliased(ReceiverRegister(), NameRegister(), SlotRegister(),
+  //                    VectorRegister(), kRootRegister));
+  int len = arraysize(registers) - kStackArgumentsCount;
+  data->InitializePlatformSpecific(len, registers);
 }
 
 void StoreWithVectorDescriptor::InitializePlatformSpecific(
     CallInterfaceDescriptorData* data) {
   Register registers[] = {ReceiverRegister(), NameRegister(), ValueRegister(),
                           SlotRegister(), VectorRegister()};
+  // TODO(jgruber): This DCHECK could be enabled if RegisterBase::ListOf were
+  // to allow no_reg entries.
+  // DCHECK(!AreAliased(ReceiverRegister(), NameRegister(), kRootRegister));
   int len = arraysize(registers) - kStackArgumentsCount;
   data->InitializePlatformSpecific(len, registers);
 }

src/interface-descriptors.h

@@ -601,6 +601,15 @@ class LoadWithVectorDescriptor : public LoadDescriptor {
   DECLARE_DESCRIPTOR(LoadWithVectorDescriptor, LoadDescriptor)
 
   static const Register VectorRegister();
+
+#if V8_TARGET_ARCH_IA32
+  static const bool kPassLastArgsOnStack = true;
+#else
+  static const bool kPassLastArgsOnStack = false;
+#endif
+
+  // Pass vector through the stack.
+  static const int kStackArgumentsCount = kPassLastArgsOnStack ? 1 : 0;
 };
 
 class LoadGlobalWithVectorDescriptor : public LoadGlobalDescriptor {
@@ -611,9 +620,15 @@ class LoadGlobalWithVectorDescriptor : public LoadGlobalDescriptor {
                          MachineType::AnyTagged())     // kVector
   DECLARE_DESCRIPTOR(LoadGlobalWithVectorDescriptor, LoadGlobalDescriptor)
 
+#if V8_TARGET_ARCH_IA32
+  // On ia32, LoadWithVectorDescriptor passes vector on the stack and thus we
+  // need to choose a new register here.
+  static const Register VectorRegister() { return edx; }
+#else
   static const Register VectorRegister() {
     return LoadWithVectorDescriptor::VectorRegister();
   }
+#endif
 };
 
 class FastNewFunctionContextDescriptor : public CallInterfaceDescriptor {