chore: group THUMB and select ARM instructions together (same file)

src/cpu/thumb/software_interrupt.zig

@@ -0,0 +1,22 @@
+const Bus = @import("../../Bus.zig");
+const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
+const InstrFn = @import("../../cpu.zig").ThumbInstrFn;
+
+pub fn format17() InstrFn {
+    return struct {
+        fn inner(cpu: *Arm7tdmi, _: *Bus, _: u16) void {
+            // Copy Values from Current Mode
+            const r15 = cpu.r[15];
+            const cpsr = cpu.cpsr.raw;
+
+            // Switch Mode
+            cpu.changeMode(.Supervisor);
+            cpu.cpsr.t.write(false); // Force ARM Mode
+            cpu.cpsr.i.write(true); // Disable normal interrupts
+
+            cpu.r[14] = r15; // Resume Execution
+            cpu.spsr.raw = cpsr; // Previous mode CPSR
+            cpu.r[15] = 0x0000_0008;
+        }
+    }.inner;
+}