schibo's recompiler doc mentions using a two-dimensional array instead of a one-dimensional array for keeping track of block start addresses for memory reasons. How does this save memory? I'm not a C expert by any stretch of the imagination, but doesn't an array with dimensions [x][y] have the same number of elements and same memory usage as a one-dimensional [x*y] array? Do the memory savings come from something else that I wasn't paying attention to? Any help is appreciated.
schibo's recompiler doc - block addresses
- Thread starter Ex-Cyber
- Start date
schibo
Emulator Developer
Hi,
Thanks. The doc is wrong.
But the issue is the index. If you are looking up an address such as 0x80001000, LookupTable[0x80001000] is a large array, whereas if you used LookupTable[0x8000], the table returns the base address, and then all you need to do is add the displacement, assuming the memory being looked up is contiguous.
Like this:
uint32* LookupPtr;
LookupPtr = (uint32 *) ((uint8 *) LookupTable[pc >> 16] + (uint16) pc);
Thanks. The doc is wrong.
But the issue is the index. If you are looking up an address such as 0x80001000, LookupTable[0x80001000] is a large array, whereas if you used LookupTable[0x8000], the table returns the base address, and then all you need to do is add the displacement, assuming the memory being looked up is contiguous.
Like this:
uint32* LookupPtr;
LookupPtr = (uint32 *) ((uint8 *) LookupTable[pc >> 16] + (uint16) pc);