bcx partially implemented

core/broadway/instructions.cpp

@@ -27,14 +27,54 @@ void broadway::bx(ircolib::u32 instr) {
     const bool link = instr & 1;
     const bool absolute = instr & 2;
 
-    ircolib::s32 LI = (ircolib::s32(instr << 6) >> 6) & 0x03FFFFFC;
+    ircolib::s32 li = (ircolib::s32(instr << 6) >> 6) & 0xFFFFFFFC;
     if (!absolute)
-        LI += pc - 4;
+        li += pc - 4;
 
     if (link)
         lr = pc;
 
-    pc = LI;
+    pc = li;
+}
+
+void broadway::bcx(ircolib::u32 instr) {
+    const bool link = instr & 1;
+    const bool absolute = instr & 2;
+
+    ircolib::s32 bd = (ircolib::s32(instr << 16) >> 16) & 0xFFFFFFFC;
+    if (!absolute)
+        bd += pc - 4;
+
+    if (!ircolib::is_bit_set<ircolib::u32, 25>(instr))
+        ircolib::panic("broadway::bcx unimplemented variants with bit 25 == 0");
+
+    if (ircolib::is_bit_set<ircolib::u32, 23>(instr)) { // always
+        if (link)
+            lr = pc;
+
+        pc = bd;
+        return;
+    }
+
+    if (ircolib::is_bit_set<ircolib::u32, 22>(instr)) { // --ctr == 0
+        if (--ctr != 0)
+            return;
+
+        if (link)
+            lr = pc;
+
+        pc = bd;
+        return;
+    }
+
+    // --ctr != 0
+    if (--ctr == 0)
+        return;
+
+    if (link)
+        lr = pc;
+
+    pc = bd;
 }
 
 void broadway::move_spr(ircolib::u32 instr) {