Melvin Smith <[EMAIL PROTECTED]> wrote: > Parrot currently assumes INTVAL size == OPCODE size because > both get configured as the same integral type, although you can choose > to override it, it is not supported to choose INTVAL > OPCODE, though > the inverse is. So storing it in the header is probably redundant, unless > we change the rules.
1) opcode_t is the size of opcodes, but has to hold pointers too, for prederef and such. I'd name it the natural wordsize. 2) INTVAL is a VM register category holding some integers, which the VM can work with -- as is FLOATVAL. Your conlusion above is just reverse. The whole machinery relies on the fact that we can say sizeof(opcode_t) == sizeof(void *). sizeof(INTVAL) is AFAIK not related to that in any way. 3) If there is such a configure option, and it doesn't work its a mistake. > B) For bytecodes to be portable we have to have some rules about > standard sizes. Yes, we can unpack a 64-bit bytecode on a 32-bit > CPU, but INTVAL constants (non-PMC) get truncated. The concept of having INTVAL constants inside the opcodes is wrong from a general POV. Please have a look at e.g jit/arm/ what immediate constants are requiring as work arounds. > Since it is NEVER portable for someone to write code using the Ix > registers with values > than 32-bit, we have to make a rule. which is, Parrot core types, their usage and the concept needs some rework, when it comes to make 64bit INTVALs work on 32-bit CPUs. IIRC: "Make mine SuperSized" by the well known and ever forgotten Bryan C. Warnock and the discussion following!!!1 was quite informative. > lt I0, <MAXINT CONSTANT>, LOOP > Runs differently between platforms is enough reason to make > a least common denominator MAXINT the Parrot standard. Yep, thats the summary of the problem. INTVAL constants are not portable as FLOTAVAL constants aren't --if the are inline > The summary of this: > Parrot must use a PMC Int type to store portable data, so the INTVAL > should be stored as part of the PMC stream, not the bytecode > header, as we may support multiple sizes. How do you communicate the long-long-long intval constants to the PMC? > -Melvin leo
