Add support for custom calling convention passing arguments in registers

If the compiler decided to pass an argument in a register on an internal function instead of pushing it on the stack to save time, allow us to specify the register the parameter is going to be in.

DHookAddParam received another parameter to set the register.

DynamicHooks/conventions/x86MsCdecl.cpp

@@ -78,6 +78,16 @@ ke::Vector<Register_t> x86MsCdecl::GetRegisters()
 		}
 	}
 
+	// Save all the custom calling convention registers as well.
+	for (unsigned int i = 0; i < m_vecArgTypes.length(); i++)
+	{
+		if (m_vecArgTypes[i].custom_register == None)
+			continue;
+
+		// TODO: Make sure the list is unique? Set?
+		registers.append(m_vecArgTypes[i].custom_register);
+	}
+
 	return registers;
 }
 
@@ -92,7 +102,8 @@ int x86MsCdecl::GetArgStackSize()
 
 	for (unsigned int i = 0; i < m_vecArgTypes.length(); i++)
 	{
-		iArgStackSize += m_vecArgTypes[i].size;
+		if (m_vecArgTypes[i].custom_register == None)
+			iArgStackSize += m_vecArgTypes[i].size;
 	}
 
 	return iArgStackSize;
@@ -103,12 +114,36 @@ void** x86MsCdecl::GetStackArgumentPtr(CRegisters* pRegisters)
 	return (void **)(pRegisters->m_esp->GetValue<unsigned long>() + 4);
 }
 
+int x86MsCdecl::GetArgRegisterSize()
+{
+	int iArgRegisterSize = 0;
+
+	for (unsigned int i = 0; i < m_vecArgTypes.length(); i++)
+	{
+		if (m_vecArgTypes[i].custom_register != None)
+			iArgRegisterSize += m_vecArgTypes[i].size;
+	}
+
+	return iArgRegisterSize;
+}
+
 void* x86MsCdecl::GetArgumentPtr(int iIndex, CRegisters* pRegisters)
 {
+	// Check if this argument was passed in a register.
+	if (m_vecArgTypes[iIndex].custom_register != None)
+	{
+		CRegister *pRegister = pRegisters->GetRegister(m_vecArgTypes[iIndex].custom_register);
+		if (!pRegister)
+			return NULL;
+
+		return pRegister->m_pAddress;
+	}
+
 	int iOffset = 4;
 	for(int i=0; i < iIndex; i++)
 	{
-		iOffset += m_vecArgTypes[i].size;
+		if (m_vecArgTypes[i].custom_register == None)
+			iOffset += m_vecArgTypes[i].size;
 	}
 
 	return (void *) (pRegisters->m_esp->GetValue<unsigned long>() + iOffset);