I'm still working on this

src/spider/runtime/cpu/CPU.cpp

@@ -67,9 +67,10 @@ namespace spider {
 
     void CPU::fetchInstr() {
         u16 i = _reel->readU16(RI);
-        _opcode = (i >> 7) & 0x1FF;
-        _addrm = (i >> 2) & 0x1F;
-        _size = i & 0x3;
+        const u16 oc = (i >> 7);
+        _opcode = oc & 0x1FF; // GCC WHY!
+        _addrm = static_cast<u8>((i >> 2) & 0x1F);
+        _size = static_cast<u8>(i & 0x3);
         RI += 2;
     }
 
@@ -90,7 +91,7 @@ namespace spider {
         (this->*(CPU::addrModes[_addrm]))();
 
         // modify the _addrm register
-        _addrm >>= 3;
+        _addrm = static_cast<u8>((_addrm >> 3) & 0x1F);
         _addrm++;
     }
 
@@ -138,7 +139,13 @@ namespace spider {
     void CPU::reg() { // NOT FINISHED
         // Two consecutive registers can be declared
         // Shift if the top part will become .reg too
-        u8 sh = (_addrm & 0b11000 == 0b11000) * 4;
+        u8 sh = ((_addrm & 0b11000) == 0b11000) * 4;
+        u8 use = 1 - (sh >> 2); // (sh / 4)
+
+        // get byte
+        u8 reg = (_reel->readU8(RI) >> sh) & 0xF;
+        _alu = &GPR[reg];
+        RI += use;
 
         // store no-op
         _post = &CPU::imp;