CPU: Explain why some code is commented out.

src/cpu/simple/atomic.cc

@@ -730,6 +730,10 @@ AtomicSimpleCPU::tick()
             dcache_access = false; // assume no dcache access
 
             if (!fromRom) {
+                // This is commented out because the predecoder would act like
+                // a tiny cache otherwise. It wouldn't be flushed when needed
+                // like the I cache. It should be flushed, and when that works
+                // this code should be uncommented.
                 //Fetch more instruction memory if necessary
                 //if(predecoder.needMoreBytes())
                 //{