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fix(bus): replace write table with two tables for u32/u8 and u8 writes

This commit is contained in:
Rekai Nyangadzayi Musuka 2022-11-01 07:00:07 -03:00
parent c395c04a6e
commit bc52461f0f
1 changed files with 28 additions and 15 deletions
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43
src/core/Bus.zig
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@ -54,12 +54,15 @@ cpu: *Arm7tdmi,
sched: *Scheduler,
read_table: *const [table_len]?*const anyopaque,
write_table: *const [table_len]?*anyopaque,
write_tables: [2]*const [table_len]?*anyopaque,
allocator: Allocator,
pub fn init(self: *Self, allocator: Allocator, sched: *Scheduler, cpu: *Arm7tdmi, paths: FilePaths) !void {
const read_table = try allocator.create([table_len]?*const anyopaque);
const write_table = try allocator.create([table_len]?*anyopaque);
const write_tables = try allocator.alloc(?*anyopaque, 2 * table_len); // Copy of the write table just for u8 writes
const left_write: *[table_len]?*anyopaque = write_tables[0..table_len];
const right_write: *[table_len]?*anyopaque = write_tables[table_len .. 2 * table_len];
self.* = .{
.pak = try GamePak.init(allocator, cpu, paths.rom, paths.save),
@ -75,14 +78,18 @@ pub fn init(self: *Self, allocator: Allocator, sched: *Scheduler, cpu: *Arm7tdmi
.sched = sched,
.read_table = read_table,
.write_table = write_table,
.write_tables = .{ left_write, right_write },
.allocator = allocator,
};
// read_table, write_table, and *Self are not restricted to the lifetime
// read_table, write_tables, and *Self are not restricted to the lifetime
// of this init function so we can initialize our tables here
fillReadTable(self, read_table);
fillWriteTable(self, write_table);
// Internal Display Memory behavious unusually on 8-bit reads
// so we have two different tables depending on whether there's an 8-bit read or not
fillWriteTable(u16, self, left_write); // T could also be u32 here
fillWriteTable(u8, self, right_write);
}
pub fn deinit(self: *Self) void {
@ -92,7 +99,11 @@ pub fn deinit(self: *Self) void {
self.bios.deinit();
self.ppu.deinit();
self.allocator.destroy(self.read_table);
self.allocator.destroy(self.write_table);
// This is so I can deallocate the original `allocator.alloc`. I have to re-make the type
// since I'm not keeping it around, This is very jank and bad though
// FIXME: please figure out another way
self.allocator.free(@ptrCast([*]const ?*anyopaque, self.write_tables[0][0..])[0 .. 2 * table_len]);
self.* = undefined;
}
@ -122,7 +133,10 @@ fn fillReadTable(bus: *Self, table: *[table_len]?*const anyopaque) void {
}
}
fn fillWriteTable(bus: *Self, table: *[table_len]?*const anyopaque) void {
fn fillWriteTable(comptime T: type, bus: *Self, table: *[table_len]?*const anyopaque) void {
comptime std.debug.assert(T == u32 or T == u16 or T == u8);
const vramMirror = @import("ppu.zig").Vram.mirror;
for (table) |*ptr, i| {
const addr = page_size * i;
@ -135,9 +149,9 @@ fn fillWriteTable(bus: *Self, table: *[table_len]?*const anyopaque) void {
// Internal Display Memory
// FIXME: Different table for different integer width writes?
0x0500_0000...0x05FF_FFFF => null, // unique behaviour on 8-bit reads
0x0600_0000...0x06FF_FFFF => null, // Has some behaviour depending on DISPCNT values
0x0700_0000...0x07FF_FFFF => &bus.ppu.oam.buf[addr & 0x3FF], // 8-bit values ignored
0x0500_0000...0x05FF_FFFF => if (T != u8) &bus.ppu.palette.buf[addr & 0x3FF] else null,
0x0600_0000...0x06FF_FFFF => if (T != u8) &bus.ppu.vram.buf[vramMirror(addr)] else null,
0x0700_0000...0x07FF_FFFF => if (T != u8) &bus.ppu.oam.buf[addr & 0x3FF] else null,
// External Memory (Game Pak)
0x0800_0000...0x0DFF_FFFF => null, // ROM
@ -366,12 +380,8 @@ pub fn write(self: *Self, comptime T: type, unaligned_address: u32, value: T) vo
// We're doing some serious out-of-bounds open-bus writes, they do nothing though
if (page > table_len) return;
if (self.write_table[page]) |some_ptr| {
if (self.write_tables[if (T == u8) 1 else 0][page]) |some_ptr| {
// We have a pointer to a page, cast the pointer to it's underlying type
// 8-bit OAM reads do nothing
if (T == u8 and @truncate(u8, unaligned_address >> 24) == 0x07) return;
const Ptr = [*]T;
const alignment = @alignOf(std.meta.Child(Ptr));
const ptr = @ptrCast(Ptr, @alignCast(alignment, some_ptr));
@ -380,6 +390,9 @@ pub fn write(self: *Self, comptime T: type, unaligned_address: u32, value: T) vo
// lower bits of the address as the GBA would
ptr[forceAlign(T, offset) / @sizeOf(T)] = value;
} else {
// we can return early if this is an 8-bit OAM write
if (T == u8 and @truncate(u8, unaligned_address) == 0x07) return;
self.slowWrite(T, unaligned_address, value);
}
}