Code cleanup in preparation for x64 backend.

- Use InvokeDexCallingConventionVisitor for setting
  up HParameterValues
- Use kVregSize instead of kX86WordSize when dealing with
  virtual registers.

Change-Id: Ia520223010194c70a3ff0ed659077f55cec4e7d8
diff --git a/compiler/optimizing/code_generator_x86.h b/compiler/optimizing/code_generator_x86.h
index 9108f80..f22890e 100644
--- a/compiler/optimizing/code_generator_x86.h
+++ b/compiler/optimizing/code_generator_x86.h
@@ -28,6 +28,37 @@
 
 class CodeGeneratorX86;
 
+static constexpr Register kParameterCoreRegisters[] = { ECX, EDX, EBX };
+static constexpr RegisterPair kParameterCorePairRegisters[] = { ECX_EDX, EDX_EBX };
+static constexpr size_t kParameterCoreRegistersLength = arraysize(kParameterCoreRegisters);
+
+class InvokeDexCallingConvention : public CallingConvention<Register> {
+ public:
+  InvokeDexCallingConvention()
+      : CallingConvention(kParameterCoreRegisters, kParameterCoreRegistersLength) {}
+
+  RegisterPair GetRegisterPairAt(size_t argument_index) {
+    DCHECK_LT(argument_index + 1, GetNumberOfRegisters());
+    return kParameterCorePairRegisters[argument_index];
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(InvokeDexCallingConvention);
+};
+
+class InvokeDexCallingConventionVisitor {
+ public:
+  InvokeDexCallingConventionVisitor() : gp_index_(0) {}
+
+  Location GetNextLocation(Primitive::Type type);
+
+ private:
+  InvokeDexCallingConvention calling_convention;
+  uint32_t gp_index_;
+
+  DISALLOW_COPY_AND_ASSIGN(InvokeDexCallingConventionVisitor);
+};
+
 class LocationsBuilderX86 : public HGraphVisitor {
  public:
   LocationsBuilderX86(HGraph* graph, CodeGeneratorX86* codegen)
@@ -42,6 +73,7 @@
 
  private:
   CodeGeneratorX86* const codegen_;
+  InvokeDexCallingConventionVisitor parameter_visitor_;
 
   DISALLOW_COPY_AND_ASSIGN(LocationsBuilderX86);
 };