imjasonh/nescript
1
0
Fork 0
mirror of https://github.com/imjasonh/nescript synced 2026-07-13 02:59:36 +00:00
Code Activity

codegen: support banked → banked cross-bank function calls

Browse source 
Programs that put functions in switchable banks can now call across
bank boundaries — `bank A { fun step() { helper() } }` where
`helper` lives in `bank B` used to panic in the IR codegen. Three
small pieces unblock it:

1. **Generic trampoline.** `runtime/gen_bank_trampoline` no longer
   takes a `fixed_bank_index` argument. Instead it reads the
   caller's current bank from `ZP_BANK_CURRENT`, pushes it on the
   hardware stack, switches to the target, JSRs the entry, then
   pulls and restores the saved bank. The same per-callee stub
   works for fixed→banked and banked→banked direction; nested
   trampolines compose because each PHA/PLA pair sits inside its
   own JSR/RTS frame. `gen_mapper_init` seeds `ZP_BANK_CURRENT`
   with the fixed bank index for any banked mapper so the very
   first cross-bank call from the fixed bank still restores to
   the fixed bank (matching pre-banked-banked semantics).

2. **Codegen drops the panic.** The `Some(from), Some(to)` arm in
   the call-resolution switch now emits `JSR __tramp_<name>` like
   the fixed→banked case instead of panicking. Banked→fixed calls
   still go direct (the fixed bank is always mapped at $C000).

3. **Bank-namespaced local labels.** Two banks emitting the same
   `__ir_cmp_e_8` would trip the linker's discovery-pass duplicate-
   label check the moment any banked code generated a comparison.
   The new `local_label_suffix` helper prefixes the suffix with the
   current bank name when banked code is being emitted, leaving
   fixed-bank label generation untouched (so existing examples are
   byte-identical apart from the trampoline / init bytes
   themselves).

The new `examples/uxrom_banked_to_banked.ne` demonstrates the path
end-to-end: `bank Logic { fun step() { ... clamp() } }` calls
`bank Helpers { fun clamp() { ... } }` once per frame. The harness
golden is committed alongside it. The five existing banked example
ROMs change byte-for-byte because of the new trampoline shape and
the seed-ZP_BANK_CURRENT init, but their emulator goldens still
match exactly — observable behaviour is unchanged.

https://claude.ai/code/session_01KEczoNUX3WmcFLfq6iAQxB
This commit is contained in:
Claude 2026-04-15 02:37:19 +00:00
parent 7294ae3efa
commit db3a4adc57
No known key found for this signature in database
15 changed files with 403 additions and 66 deletions
Download patch file Download diff file Expand all files Collapse all files

4
src/linker/mod.rs
View file

@ -341,7 +341,6 @@ impl Linker {
// maps to $C000-$FFFF and one of the switchable banks maps
// to $8000-$BFFF.
let total_banks = switchable_banks.len() + 1;
let fixed_bank_index = total_banks - 1;
// Discovery pass: assemble each switchable bank that has
// its own instruction stream so we know what labels live
@ -447,8 +446,6 @@ impl Linker {
// which switchable bank is currently mapped at $8000.
if self.mapper != Mapper::NROM {
all_instructions.extend(runtime::gen_bank_select(self.mapper));
#[allow(clippy::cast_possible_truncation)]
let fixed_bank_num = fixed_bank_index as u8;
for (i, bank) in switchable_banks.iter().enumerate() {
if bank.trampolines.is_empty() {
continue;
@ -460,7 +457,6 @@ impl Linker {
&tramp.tramp_label,
&tramp.entry_label,
bank_num,
fixed_bank_num,
));
}
}