While all base registers can be used for any purpose at any time (this
is why the with instruction has hard-absolute modes: you can never get
permanently lost), qfcc currently uses the convention of register 0 for
globals and register 1 for stack locals (params, locals, function args).
The register used to access a def is stored in the def and that is used
to set the register bits in the instruction opcode.
The def code actually doesn't know anything about any conventions: it
assumes all defs are global for non-temp defs (the function code updates
the defs before emitting code) and the current function provides the
register to use for any temp defs allocated while emitting code.
Seems to work well, but debug is utterly messed up (not surprised, that
will be tricky).
Still need to get the base register index into the instructions, but I
think this is it for basic code generation. I should be able to start
testing Ruamoko properly fairly soon :)
ldconst isn't implemented yet but the plan is to load various constants
(eg, 0, 1, 2, pi, e, ...).
Stack adjust is useful for adding an offset to the stack pointer without
having to worry about finding it (and it checks for alignment).
nop is just that :)
Thanks to the use/def/kill lists attached to statements for pseudo-ops,
it turned out to be a lot easier to implement flow analysis (and thus
dags processing) than I expected. I suspect I should go back and make
the old call code use them too, and probably several other places, as
that will greatly simplify the edge setting.
The means that the actual call expression is not in the statement lint
of the enclosing block expression, but just its result, whether the call
is void or not. This actually simplifies several things, but most
importantly will make Ruamoko calls easier to implement.
The test is because I had some trouble with double-calls, and is how I
found the return-postop issue :P
Commit 76b3bedb72 broke more than just the
swap test, but at least I know I need to get an edge in the dag.
Currently, the following code is generated: return and add are reversed.
../tools/qfcc/test/return-postop.r:8: return counter++;
0001 store.i counter, .tmp0
0002 return .tmp0
0003 add.i .tmp0, (1), counter
However, I don't want to deal with it right now, so it's marked XFAIL.
Since Ruamoko now uses the stack for parameters and locals, parameters
need to come after locals in the address space (instead of before, as in
v6 progs). Thus use separate spaces for parameters and locals regardless
of the target, then stitch them together appropriately for the target.
The third space is used for allocating stack space for arguments to
called functions. It us not used for v6 progs, and comes before locals
in Ruamoko progs.
Other than the return value, and optimization (ice, not implemented)
calls in Ruamoko look like they'll work.
Thanks to me having done something right 20 years ago, that was pretty
easy :). The two boolean types aren't supported yet because I haven't
decided on just how to represent their types in qfcc.
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.
Terminal apps effectively always have focus (unless I find a way to know
when an xterm loses/gains focus). Fixes input-app not updating on evdev
events.
This seems to be the most reasonable approach to allocating space for
function call parameters without using push and pop (or adding to the
stack pointer), though it's probably good even when using push and pop
to help keep things aligned.
My little test program now builds with the Ruamoko ISA :)
void cp (int *dst, int *src, int count)
{
while (count--) {
*dst++ = *src++;
}
}
Calls are broken (unimplemented), and non-void returns are not likely to
work either (only partially implemented).
Operand width is encoded in the instruction opcode, so the width needs
to be accounted for in order to select the correct instruction. With
this, my little test generates correct code for the ruamoko ISA (except
for return, still fails).
It turned out that address mode B was redundant as C with 0 offset
(immediate) was the same (except for the underlying C code of course,
but adding st->b is very cheap). This allowed B to be used for
entity.field for all transfer operations. Thus instructions 0-3 are now
free as load E became load B, and other than the specifics of format
codes for statement printing, transfers+lea are unified.
For the most part, it wasn't too bad as it's just a rotation of the
operands for some instructions (store, assign, branch), but dealing with
all the direct accesses to specific operands was a small pain. I am very
glad I made all those automated tests :)
This makes the v6p instruction table consistent with the ruamoko
instruction table, and clears up some of the ugliness with the load,
store, and assign instructions (. .= and = are now spelled out). I think
I'd still prefer an enum code (faster) but at least this is more
readable.
Missed this case in duplicate_type. Allows "short foo" and
"sizeof(short)" (even though qfcc and the engine have two ideas of the
size: I expect trouble later).
long is ignored for double, and v6p progs are stuck with 32 bits for
longs (don't feel like extending v6p any further), but the basics are
there for Ruamoko.
short is ignored for ints because the minimum size is 32, and signed is
just noise for ints anyway (and no chars, so...).
unsigned, however, is finally implemented properly (or at least seems to
be working correctly: tests pass after getting things compiling again,
and lt.u is used where it should be :)
Attempting to add ev_ushort caused ptraliasenc to break, but that was
because it was already broken: I had implemented the scan of the xdef
table incorrectly, thus adding only 1 ev type resulted in the walked
pointer being out of phase with its data due to it first passing over
the type encodings (which is why adding long and ulong didn't cause any
obvious trouble).
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).
