[ia32] Remove kRootRegister from default interface descriptors

This is another step towards a kRootRegister on ia32 and removes
kRootRegister from generic interface descriptors.

Drive-by: Better error message for type mismatches in machine graph
verification.
Drive-by: Use PreserveRootIA32 register config for all builtins.

Bug: v8:6666
Change-Id: I920d4d6f3085da9734f6aa3bd3ee020abbc289fc
Reviewed-on: https://chromium-review.googlesource.com/1186330Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55338}

src/compiler/machine-graph-verifier.cc

@@ -782,7 +782,8 @@ class MachineRepresentationChecker {
           str << std::endl;
         }
         str << " * input " << i << " (" << input->id() << ":" << *input->op()
-            << ") doesn't have a " << expected_input_type << " representation.";
+            << ") has a " << input_type
+            << " representation (expected: " << expected_input_type << ").";
       }
     }
     if (should_log_error) {

src/compiler/pipeline.cc

@@ -2407,8 +2407,8 @@ bool PipelineImpl::SelectInstructions(Linkage* linkage) {
     AllocateRegisters(RegisterConfiguration::Poisoning(), call_descriptor,
                       run_verifier);
 #if defined(V8_TARGET_ARCH_IA32) && defined(V8_EMBEDDED_BUILTINS)
-  } else if (data_->assembler_options().isolate_independent_code) {
-    // TODO(v8:6666): Extend support to all builtins and user code. Ensure that
+  } else if (Builtins::IsBuiltinId(data_->info()->builtin_index())) {
+    // TODO(v8:6666): Extend support to user code. Ensure that
     // it is mutually exclusive with the Poisoning configuration above; and that
     // it cooperates with restricted allocatable registers above.
     static_assert(kRootRegister == kSpeculationPoisonRegister,

src/ia32/interface-descriptors-ia32.cc

@@ -13,7 +13,14 @@ const Register CallInterfaceDescriptor::ContextRegister() { return esi; }
 
 void CallInterfaceDescriptor::DefaultInitializePlatformSpecific(
     CallInterfaceDescriptorData* data, int register_parameter_count) {
-  const Register default_stub_registers[] = {eax, ebx, ecx, edx, edi};
+#if defined(V8_TARGET_ARCH_IA32) && defined(V8_EMBEDDED_BUILTINS)
+  // TODO(jgruber,v8:6666): Keep kRootRegister free unconditionally.
+  constexpr Register default_stub_registers[] = {eax, ecx, edx, edi};
+  DCHECK(!AreAliased(eax, ecx, edx, edi, kRootRegister));
+#else
+  constexpr Register default_stub_registers[] = {eax, ebx, ecx, edx, edi};
+#endif
+  STATIC_ASSERT(arraysize(default_stub_registers) == kMaxBuiltinRegisterParams);
   CHECK_LE(static_cast<size_t>(register_parameter_count),
            arraysize(default_stub_registers));
   data->InitializePlatformSpecific(register_parameter_count,

src/interface-descriptors.h

@@ -289,7 +289,12 @@ class V8_EXPORT_PRIVATE CallInterfaceDescriptor {
   explicit name() : base(key()) {}               \
   static inline CallDescriptors::Key key();
 
+#if defined(V8_TARGET_ARCH_IA32) && defined(V8_EMBEDDED_BUILTINS)
+// TODO(jgruber,v8:6666): Keep kRootRegister free unconditionally.
+constexpr int kMaxBuiltinRegisterParams = 4;
+#else
 constexpr int kMaxBuiltinRegisterParams = 5;
+#endif
 
 #define DECLARE_DEFAULT_DESCRIPTOR(name, base)                                 \
   DECLARE_DESCRIPTOR_WITH_BASE(name, base)                                     \