feat: implement OAM

src/Bus.zig

@@ -49,7 +49,7 @@ pub fn read32(self: *const Self, addr: u32) u32 {
         // Internal Display Memory
         0x0500_0000...0x0500_03FF => self.ppu.palette.get32(addr - 0x0500_0000),
         0x0600_0000...0x0601_7FFF => self.ppu.vram.get32(addr - 0x0600_0000),
-        0x0700_0000...0x0700_03FF => std.debug.panic("[Bus:32] read from 0x{X:} in OAM", .{addr}),
+        0x0700_0000...0x0700_03FF => self.ppu.oam.get32(addr - 0x0700_0000),
 
         // External Memory (Game Pak)
         0x0800_0000...0x09FF_FFFF => self.pak.get32(addr - 0x0800_0000),
@@ -75,7 +75,7 @@ pub fn write32(self: *Self, addr: u32, word: u32) void {
         // Internal Display Memory
         0x0500_0000...0x0500_03FF => self.ppu.palette.set32(addr - 0x0500_0000, word),
         0x0600_0000...0x0601_7FFF => self.ppu.vram.set32(addr - 0x0600_0000, word),
-        0x0700_0000...0x0700_03FF => std.debug.panic("[Bus:32] wrote 0x{X:} to 0x{X:} in OAM", .{ word, addr }),
+        0x0700_0000...0x0700_03FF => self.ppu.oam.set32(addr - 0x0700_0000, word),
 
         else => log.warn("32-bit write of 0x{X:0>8} to 0x{X:0>8}", .{ word, addr }),
     }
@@ -92,7 +92,7 @@ pub fn read16(self: *const Self, addr: u32) u16 {
         // Internal Display Memory
         0x0500_0000...0x0500_03FF => self.ppu.palette.get16(addr - 0x0500_0000),
         0x0600_0000...0x0601_7FFF => self.ppu.vram.get16(addr - 0x0600_0000),
-        0x0700_0000...0x0700_03FF => std.debug.panic("[Bus:16] read from 0x{X:} in OAM", .{addr}),
+        0x0700_0000...0x0700_03FF => self.ppu.oam.get16(addr - 0x0700_0000),
 
         // External Memory (Game Pak)
         0x0800_0000...0x09FF_FFFF => self.pak.get16(addr - 0x0800_0000),
@@ -117,7 +117,7 @@ pub fn write16(self: *Self, addr: u32, halfword: u16) void {
         // Internal Display Memory
         0x0500_0000...0x0500_03FF => self.ppu.palette.set16(addr - 0x0500_0000, halfword),
         0x0600_0000...0x0601_7FFF => self.ppu.vram.set16(addr - 0x0600_0000, halfword),
-        0x0700_0000...0x0700_03FF => std.debug.panic("[Bus:16] write 0x{X:} to 0x{X:} in OAM", .{ halfword, addr }),
+        0x0700_0000...0x0700_03FF => self.ppu.oam.set16(addr - 0x0700_0000, halfword),
 
         else => log.warn("16-bit write of 0x{X:0>4} to 0x{X:0>8}", .{ halfword, addr }),
     }
@@ -134,7 +134,7 @@ pub fn read8(self: *const Self, addr: u32) u8 {
         // Internal Display Memory
         0x0500_0000...0x0500_03FF => self.ppu.palette.get8(addr - 0x0500_0000),
         0x0600_0000...0x0601_7FFF => self.ppu.vram.get8(addr - 0x0600_0000),
-        0x0700_0000...0x0700_03FF => std.debug.panic("[Bus:8] read from 0x{X:} in OAM", .{addr}),
+        0x0700_0000...0x0700_03FF => self.ppu.oam.get8(addr - 0x0700_0000),
 
         // External Memory (Game Pak)
         0x0800_0000...0x09FF_FFFF => self.pak.get8(addr - 0x0800_0000),

src/cpu/thumb/branch.zig

@@ -43,7 +43,7 @@ pub fn format19(comptime is_low: bool) InstrFn {
                 // Instruction 2
                 const old_pc = cpu.r[15];
 
-                cpu.r[15] = cpu.r[14] + (offset << 1);
+                cpu.r[15] = cpu.r[14] +% (offset << 1);
                 cpu.r[14] = old_pc | 1;
             } else {
                 // Instruction 1

src/cpu/thumb/data_transfer.zig

@@ -116,7 +116,7 @@ pub fn format10(comptime L: bool, comptime offset: u5) InstrFn {
             const rb = opcode >> 3 & 0x7;
             const rd = opcode & 0x7;
 
-            const address = cpu.r[rb] + (offset << 1);
+            const address = cpu.r[rb] + (@as(u6, offset) << 1);
 
             if (L) {
                 // LDRH

src/cpu/thumb/processing_branch.zig

@@ -18,12 +18,12 @@ pub fn format5(comptime op: u2, comptime h1: u1, comptime h2: u1) InstrFn {
                 0b00 => {
                     // ADD
                     const sum = add(false, cpu, dst, src);
-                    cpu.r[dst_idx] = if (dst_idx == 0xF) sum & 0xFFFF_FFFC else sum;
+                    cpu.r[dst_idx] = if (dst_idx == 0xF) sum & 0xFFFF_FFFE else sum;
                 },
                 0b01 => cmp(cpu, dst, src), // CMP
                 0b10 => {
                     // MOV
-                    cpu.r[dst_idx] = if (dst_idx == 0xF) src & 0xFFFF_FFFC else src;
+                    cpu.r[dst_idx] = if (dst_idx == 0xF) src & 0xFFFF_FFFE else src;
                 },
                 0b11 => {
                     // BX

src/ppu.zig

@@ -14,6 +14,7 @@ pub const Ppu = struct {
 
     vram: Vram,
     palette: Palette,
+    oam: Oam,
     sched: *Scheduler,
     framebuf: []u8,
     alloc: Allocator,
@@ -28,6 +29,7 @@ pub const Ppu = struct {
         return Self{
             .vram = try Vram.init(alloc),
             .palette = try Palette.init(alloc),
+            .oam = try Oam.init(alloc),
             .sched = sched,
             .framebuf = framebuf,
             .alloc = alloc,
@@ -158,3 +160,44 @@ const Vram = struct {
         return self.buf[idx];
     }
 };
+
+const Oam = struct {
+    const Self = @This();
+
+    buf: []u8,
+    alloc: Allocator,
+
+    fn init(alloc: Allocator) !Self {
+        const buf = try alloc.alloc(u8, 0x400);
+        std.mem.set(u8, buf, 0);
+
+        return Self{
+            .buf = buf,
+            .alloc = alloc,
+        };
+    }
+
+    pub fn get32(self: *const Self, idx: usize) u32 {
+        return (@as(u32, self.buf[idx + 3]) << 24) | (@as(u32, self.buf[idx + 2]) << 16) | (@as(u32, self.buf[idx + 1]) << 8) | (@as(u32, self.buf[idx]));
+    }
+
+    pub fn set32(self: *Self, idx: usize, word: u32) void {
+        self.buf[idx + 3] = @truncate(u8, word >> 24);
+        self.buf[idx + 2] = @truncate(u8, word >> 16);
+        self.buf[idx + 1] = @truncate(u8, word >> 8);
+        self.buf[idx] = @truncate(u8, word);
+    }
+
+    pub fn get16(self: *const Self, idx: usize) u16 {
+        return (@as(u16, self.buf[idx + 1]) << 8) | @as(u16, self.buf[idx]);
+    }
+
+    pub fn set16(self: *Self, idx: usize, halfword: u16) void {
+        self.buf[idx + 1] = @truncate(u8, halfword >> 8);
+        self.buf[idx] = @truncate(u8, halfword);
+    }
+
+    pub fn get8(self: *const Self, idx: usize) u8 {
+        return self.buf[idx];
+    }
+};