feat(cpu): implement THUMB ldmia stmia

src/cpu/thumb/format15.zig

@@ -0,0 +1,29 @@
+const std = @import("std");
+
+const Bus = @import("../../Bus.zig");
+const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
+const InstrFn = @import("../../cpu.zig").ThumbInstrFn;
+
+pub fn format15(comptime L: bool, comptime rb: u3) InstrFn {
+    return struct {
+        fn inner(cpu: *Arm7tdmi, bus: *Bus, opcode: u16) void {
+            const base = cpu.r[rb];
+
+            var address: u32 = base;
+
+            var i: usize = 0;
+            while (i < 8) : (i += 1) {
+                if ((opcode >> @truncate(u3, i)) & 1 == 1) {
+                    if (L) {
+                        cpu.r[i] = bus.read32(address);
+                    } else {
+                        bus.write32(address, cpu.r[i]);
+                    }
+                    address += 4;
+                }
+            }
+
+            cpu.r[rb] = address;
+        }
+    }.inner;
+}