It's currently only 4 (or even 3 for v6) words, but this fixes false
positives when checking for null pointers in Ruamoko progs due to
pr_return pointing to the return buffer and thus outside the progs
memory map resulting in an impossible to exceed value.
Thanks to the size of the type encoding being explicit in the encoding,
anything that tries to read the encodings without expecting the width
will simply skip over the width, as it is placed after the ev type in
the encoding.
Any code that needs to read both the old encodings and the new can check
the size of the basic encodings to see if the width field is present.
I abandoned the reason for doing it (adding a pile of vector types), but
I liked the cleanup. All the implementations are hand-written still, but
at least the boilerplate stuff is automated.
This cleans up dprograms_t, making it easier to read and see what chunks
are in it (I was surprised to see only 6, the explicit pairs made it
seem to have more).
PR_SetupParams is new and sets up the parameter pointers so older code
that expects only up to 8 parameter will work with both v6p and Ruamoko
progs without having to check what progs are running. PR_SetupParams is
useful even when Ruamoko progs are expected as it reserves the required
space (respecting alignment) on the stack and returns a pointer to the
top (bottom? confusing) of the stack. PR_PushFrame and PR_PopFrame
need to be used around PR_SetupParams, regardless of using temp strings,
to avoid a stack leak (need to do an audit).
This is part of the work for #26 (Record resource pointer with builtin
function data). Currently, the data pointer gets as far as the
per-instance VM function table (I don't feel like tackling the job of
converting all the builtin functions tonight). All the builtin modules
that register a resources data block pass that block on to
PR_RegisterBuiltins.
The builtin and progs function data is overlaid so the extra data
doesn't cause too much memory to be used (it's actually 8 bytes smaller
now). The plan is to pre-compute the offsets based on the parameter
size and alignment data.
This will make it possible for the engine to set up their parameter
pointers when running Ruamoko progs. At this stage, it doesn't matter
*too* much, except for varargs functions, because no builtin yet takes
anything larger than a float quaternion, but it will be critical when
double or long vec3 and vec4 values are passed.
Just 32-bit rounding to next higher power of two, and base 2 logarithm.
Most importantly, they are suitable for use in initializers as they are
constant in, constant out.
I found the docs in PR_ExecuteProgram and PR_CallFunction to be a little
confusing, so making it explicit that PR_ExecuteProgram calls
PR_CallFunction and that PR_CallFunction should be called only in a
builtin seemed like a good idea.
And fix an incorrect definition for RETURN_QUAT.
Prefixed MAX_STACK_DEPTH and LOCALSTACK_SIZE (and LOCALSTACK_SIZE got an
extra _).
The rest is just edits to documentation comments.
Due to how OP_RETURN works, a destination is required for any function
returning data, but the caller may not have allocated any space for the
value. Thus the VM maintains a buffer into which the data can be put and
ignored. It also makes a good place for return values when the engine
calls Ruamoko code as trusting progs code with return sizes seems like a
recipe for disaster, especially if the return location is on the C
stack.
And provide a table for such for qfcc and the like. With this, using
pr_double_t (for example) in C will cause the double value to always be
8-byte aligned and thus structures shared between gcc and qfcc will be
consistent (with a little fuss to take care of the warts).
And other related fields so integer is now int (and uinteger is uint). I
really don't know why I went with integer in the first place, but this
will make using macros easier for dealing with types.
They are both gone, and pr_pointer_t is now pr_ptr_t (pointer may be a
little clearer than ptr, but ptr is consistent with things like intptr,
and keeps the type name short).
This required delaying the setting of the return pointer by call until
after the current pointer had been saved, and thus passing the desired
pointer into PR_CallFunction (which does have some advantages for C
functions calling progs functions, but some dangers too (should ensure a
128 byte (32 word) buffer when calling untrusted code (which is any,
really)).
This fixes the issue of the data stack not being restored properly
because the returning function needs to return a value from its local
variables (stored on the stack) and accessing stack data below the stack
pointer is a bad idea (sure, no interrupts yet, but who knows...).
I don't know why they were ever signed (oversight at id and just
propagated?). Anyway, this resulted in "unsigned" spreading a bit, but
all to reasonable places.
This has been a long-held wishlist item, really, and I thought I might
as well take the opportunity to add the instructions. The double
versions of STATE require both the nextthink field and time global to be
double (but they're not resolved properly yet: marked with
"FIXME double time" comments).
Also, the frame number for double time state is integer rather than
float.
While it doesn't cover the addressing modes, it does match the bit
pattern used in the Ruamoko instruction set. It will make selecting
branch instructions easier (especially for Ruamoko).
In some cases, gcc-11 does a good enough job translating normal looking
C expressions so use just those, but other times need to dig around for
an appropriate intrinsic.
Also, now need to disable psapi warnings when compiling for anything
less than avx.
And partial implementations in qfcc (most places will generate an
internal error (not implemented) or segfault, but some low-hanging fruit
has already been implemented).
As I expect to be tweaking things for a while, it's part of the build
process. This will make it a lot easier to adjust mnemonics and argument
formats (tweaking the old table was a pain when conventions changed).
It's not quite done as it still needs arg widths and types.
While working on the new opcode table, I decided a lot of the names were
not to my liking. Part of the problem was the earlier clash with the
v6p opcode names, but that has been resolved via the v6p tag.
Always setting w to 0 made it impossible to use the resulting 4d vectors
in division-based operations as they would result in divide-by-zero and
thus an unavoidable exception (CPUs don't like integer div-by-zero).
I'll probably add similar for float and double, but they're not as
critical as they'll just give inf or nan. This also increases my doubts
about the value of keeping 3d vector operations.
Float bit-ops as well.
Also, add q*v4 and v4*q instructions. There are currently 48 free
opcodes, and I might remove the scale instructions, but they could be
useful as expanding a single float to a vector would take 3 instructions
(copy to temp, swizzle-expand temp, multiply, vs just scale).
It turns out gcc optimizes the obvious code nicely. It doesn't do so
well for cmul, but I decided to use obvious code anyway (the instruction
counts were the same, so maybe it doesn't get better for a single pair
of operands).
