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Thankfully multiplication, like addition, is the same under 2s
complement as it is for unsigned numbers. So I just need to implement
those versions to be fine.
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By default I initialise the registers with 8 words, though this may
not be necessary for your purposes.
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This is because comparators may apply to signed types, so I need to
use the right parsing function.
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This is using the comparators and a jump-if
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As registers may be theoretically infinite in number, we should use
the largest size possible when referring to them in bytecode (a word).
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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.
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This means the stack should be heap allocated, which makes sense as
beyond 1KB one should really be using the heap rather than the stack.
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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.
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This is only new data allocated, so it's a very careful procedure.
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Much simpler, uses a switch case which is a much faster method of
doing the parsing. Though roughly equivalent in terms of LOC, I feel
that this is more extensible
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More useful tokens, in particular for each opcode possible. This
makes parsing a simpler task to reason as now we're just checking
against an enum rather than doing a string check in linear time.
It makes more sense to do this at the tokeniser as the local data from
the buffer will be in the cache most likely as the buffer is
contiguously allocated. While it will always be slow to do linear
time checks on strings, when doing it at the parser we're having to
check strings that may be allocated in a variety of different places.
This means caching becomes a harder task, but with this approach we're
less likely to have cache misses as long as the buffer stays there.
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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.
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This pushes a datum of the same type as the operands, which is why it
cannot use the comparator macro as that always pushes bytes.
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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.
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As strto(ul|ll) allow the parsing of hex literals of the form `0x`, we
allow lexing of hex literals which start with `x`.
They're lexed into C hex literals which work for strtol.
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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.
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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).
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So much reused code, I definitely need to find a way to make this cleaner.
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For each type T there is the signed version s_T
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As it has no dependencies on vm specifically, and it's more necessary
for any vendors who wish to target the virtual machine, it makes more
sense for inst to be a lib module rather than a vm module.
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Just need to call their unsigned versions.
All comparators should push bytes as it makes return types uniform.
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otherwise
Changed VERBOSE checks to ensure a degree of information.
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Will cause error if used currently, which is fine.
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Comparing signed and unsigned versions of numbers. Same for EQ as
well.
Notice the irregular pattern of BYTE, CHAR, INT, HWORD,LONG,WORD as
OPCODE_IS_TYPE requires the subcodes to be surrounded by BYTE and
WORD.
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Currently only for invalid character literals, but still a possible
problem.
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Just takes the character literally as a number.
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All objects target LIB anyway, so VERBOSE is a universal macro for
this code base.
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Prints useful and pretty messages when verbose being at least 1.
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This is due to checking for equality instead of just greater than in
darr->used against darr->available.
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Use the push.* instructions to see this.
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Provides calling conventions, ensures parser and lexer are working
correctly. Will be updated as more instructions are introduced and
supported in the assembler.
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Pretty simple implementation, I've stopped printing the tokens cos I
think the lexer is done.
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Introduced some functions to parse differing types of opcodes. Use
the same style of a.b.c... for namespacing or type specification for
certain opcodes. Bit hacky and not tested, but does work.
Parse errors can be reported with an exact location using the token
column, line.
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Easier to do it here than at the parser.
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Accurate error reporting can be introduced using this.
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Default C just lets overflows occur for subtraction, so this macro
will default to 0 if the subtraction causes an overflow.
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Just prints instructions so far.
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Though we deal with unsigned numbers internally, it should be possible
to read and manipulate negative numbers through 2s complement. Later
on we'll add support for signed operations via 2s complement, so this
should be allowed.
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