PageTable: move backing addresses to a children class as the CPU page table does not need them.

This PR aims to reduce the memory usage in the CPU page table by moving
GPU specific parameters into a child class. This saves 1Gb of Memory for
most games.

1 files changed, 11 insertions, 1 deletions

diff --git a/src/common/page_table.cpp b/src/common/page_table.cpp
index 69b7abc54..566b57b62 100644
--- a/src/common/page_table.cpp
+++ b/src/common/page_table.cpp
@@ -16,7 +16,6 @@ void PageTable::Resize(std::size_t address_space_width_in_bits) {
 
     pointers.resize(num_page_table_entries);
     attributes.resize(num_page_table_entries);
-    backing_addr.resize(num_page_table_entries);
 
     // The default is a 39-bit address space, which causes an initial 1GB allocation size. If the
     // vector size is subsequently decreased (via resize), the vector might not automatically
@@ -25,6 +24,17 @@ void PageTable::Resize(std::size_t address_space_width_in_bits) {
 
     pointers.shrink_to_fit();
     attributes.shrink_to_fit();
+}
+
+BackingPageTable::BackingPageTable(std::size_t page_size_in_bits) : PageTable{page_size_in_bits} {}
+
+BackingPageTable::~BackingPageTable() = default;
+
+void BackingPageTable::Resize(std::size_t address_space_width_in_bits) {
+    PageTable::Resize(address_space_width_in_bits);
+    const std::size_t num_page_table_entries = 1ULL
+                                               << (address_space_width_in_bits - page_size_in_bits);
+    backing_addr.resize(num_page_table_entries);
     backing_addr.shrink_to_fit();
 }