struct.c is used for the general construction, inspection and deletion
of the virtual machine structure (vm_t). runtime defines the
execution routines, error enum, lookup tables, etc.
Firstly abuse OPCODE_DATA_TYPE along with integer arithmetic to do a
POP_ROUTINE table lookup (no more ugly conditionals). Then make a
format string table which we can lookup using the same data type.
Same method as when simplifying OP_POP's implementation: use the
lookup table along with OPCODE_DATA_TYPE abuse. In this case I made a
lookup table called OP_POP for this method to work, but it wasn't difficult.
OP_PUSH: Increment program pointer iff no error from PUSH_ROUTINE call
STACK_ROUTINES: Same as OP_PUSH
RET: Pop off the call stack iff the jump to the address was good.
This simple fix made the routine for OP_POP not require an additional
dispatch step on top of the conditional due to OPCODE_DATA_TYPE,
instead using data_type_t as a map from an opcode's base type to a
specific type.
This "header" is now embedded directly into the struct. The semantic
of a header never really matters in the actual runtime anyway, it's
only for bytecode (de)serialising.
Though practically this would work, as the storage for the half word is
not limited in any way, nevertheless it isn't syntactically right and
it's better to fix now.
When an error occurred, because prog->ptr was incremented beforehand
the trace would show the next instruction as the culprit rather than
the actual instruction. This commit fixes that by incrementing the
program if and only if the command was run successfully.
Very barebones, essentially a simple refactor.
I need to introduce a feature to append to a program as well, but as
it's a flexible structure it will likely have to be functional.
Happened because we weren't printing all relevant words due to
naturally flooring the result of division. Here I ceil the division
to ensure we get the maximal number of words necessary.
Very easy, they just pop a word then defer to their normal versions.
This is probably the best case where a macro works directly so I
didn't even need to write a function form for them first. One thing
is that then names for the macros are quite bad right now, probably
need renaming.
Pretty simple, required some new types of errors. Obviously there's
space for a macro for the differing instruction implementations, but
these things need to be tested a bit more before I can do that.
As PUSH_REGISTER and MOV have the same signature of taking a word as
input, DUP may as well be part of it.
This leads to a larger discussion about how signatures of functions
matter: I may need to do a cleanup at some point.
word register 0 refers to the first 8 bytes of the dynamic array.
Hence the used counter should be at least 8 bytes. This deals with
those issues. Also print more useful information in
vm_print_registers (how many byte|hword|word registers are currently
in use, how many are available).
Lucky surprise: OP_PLUS follows the same principle rules as the
bitwise operators in that they return the same type as the input.
Therefore I can simply use the same macro to implement it and MULT as
those. Very nice.
This is because: say we have {a, b} where a is on top of the stack. A
comparator C applies in the order C(b, a) i.e. b `C` a. The previous
version did a `C` b which was wrong.
Stack based machines generally need "variable space". This may be
quite via a symbol-to-word association a list, a hashmap, or some
other system. Here I decide to go for the simplest: extending the
register system to a dynamic/infinite number of them. This means, in
practice, that we may use a theoretically infinite number of indexed
words, hwords and bytes to act as variable space. This means that the
onus is on those who are targeting this virtual machine to create
their own association system to create syntactic variables: all the
machinery is technically installed within the VM, without the veneer
that causes extra cruft.
A negative number under 2s complement can never be equal to its
positive as the top bit *must* be on. If two numbers are equivalent
bit-by-bit then they are equal for both signed and unsigned numbers.
Anything other than char (which can just use print.byte to print the
hex) and byte (which prints hexes anyway), all other types may be
forced to print a hex rather than a number if PRINT_HEX is 1.
I've made a single macro which defines a function through some common
metric, removing code duplication. Not particularly readable per se,
but using a macro expansion in your IDE allows one to inspect the code.
These new members are just signed versions of the previous members.
This makes type punning and usage for signed versions easier than
before (no need for memcpy).
