src/cpu/thumb/block_data_transfer.zig

@@ -50,47 +50,23 @@ pub fn format14(comptime L: bool, comptime R: bool) InstrFn {
 pub fn format15(comptime L: bool, comptime rb: u3) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, bus: *Bus, opcode: u16) void {
-            var address = cpu.r[rb];
-            const end_address = cpu.r[rb] + 4 * countRlist(opcode);
+            const base = cpu.r[rb];
 
-            if (opcode & 0xFF == 0) {
-                if (L) cpu.r[15] = bus.read32(address) else bus.write32(address, cpu.r[15] + 4); // TODO: Why is this r[15] + 4?
-                cpu.r[rb] += 0x40;
-                return;
-            }
-
-            var i: u4 = 0;
-            var first_write = true;
+            var address: u32 = base;
 
+            var i: usize = 0;
             while (i < 8) : (i += 1) {
-                if (opcode >> i & 1 == 1) {
+                if ((opcode >> @truncate(u3, i)) & 1 == 1) {
                     if (L) {
                         cpu.r[i] = bus.read32(address);
                     } else {
                         bus.write32(address, cpu.r[i]);
                     }
-
-                    if (!L and first_write) {
-                        cpu.r[rb] = end_address;
-                        first_write = false;
-                    }
-
                     address += 4;
                 }
             }
 
-            if (L and opcode >> rb & 1 != 1) cpu.r[rb] = address;
+            cpu.r[rb] = address;
         }
     }.inner;
 }
-
-inline fn countRlist(opcode: u16) u32 {
-    var count: u32 = 0;
-
-    comptime var i: u4 = 0;
-    inline while (i < 8) : (i += 1) {
-        if (opcode >> (7 - i) & 1 == 1) count += 1;
-    }
-
-    return count;
-}

src/cpu/thumb/data_transfer.zig

@@ -44,14 +44,8 @@ pub fn format78(comptime op: u2, comptime T: bool) InstrFn {
                         cpu.r[rd] = std.math.rotr(u32, @as(u32, value), 8 * (address & 1));
                     },
                     0b11 => {
-                        // LDRSH
-                        const value = if (address & 1 == 1) blk: {
-                            break :blk u32SignExtend(8, bus.read8(address));
-                        } else blk: {
-                            break :blk u32SignExtend(16, bus.read16(address));
-                        };
-
-                        cpu.r[rd] = std.math.rotr(u32, value, 8 * (address & 1));
+                        // LDSH
+                        cpu.r[rd] = u32SignExtend(16, @as(u32, bus.read16(address & 0xFFFF_FFFE)));
                     },
                 }
             } else {