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jit: retire the (false,false) walker catch-link arm in flatten_graph #819

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Merged
youknowone merged 1 commit into from
Jul 27, 2026
Merged

jit: retire the (false,false) walker catch-link arm in flatten_graph #819

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38 changes: 7 additions & 31 deletions pyre/pyre-jit/src/jit/flatten.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1874,37 +1874,13 @@ impl<'a> GraphFlattener<'a> {
self.emitline(normal_label);
let mut captured_all = false;
for link in &catch_links {
let payload_shape = {
let link_borrow = link.borrow();
(
link_borrow.last_exception.is_some(),
link_borrow.last_exc_value.is_some(),
)
};
match payload_shape {
(false, false) => {
// Structural adaptation for pyre's bytecode-level
// graph builder. RPython `flowcontext.py:130-156
// guessexception` closes a canraise block with
// `exits[0]` as the sole normal link and all
// following links seeded via `Link.extravars`.
// Pyre's PC-sequential walker can leave an
// additional normal/explicit-raise edge after
// the first slot. Such a link is not an
// exception match arm; flatten it with ordinary
// `make_link` so final exceptblock targets still
// lower through `make_return`, and keep
// `make_exception_link` reserved for seeded
// exception links as upstream expects.
self.make_link(link, false);
continue;
}
(true, true) => {}
(last_exception, last_exc_value) => panic!(
"canraise catch link payload partially seeded: \
last_exception={last_exception}, last_exc_value={last_exc_value}",
),
}
// `flatten.py:223-233 insert_exits` lowers every catch link
// (`block.exits[1:]`) through `make_exception_link`, which
// asserts both `last_exception` and `last_exc_value` are seeded
// (`flatten.py:161-162`). There is no ordinary-`make_link` arm
// for a catch link: one that is not a fully seeded exception
// link is a graph-construction bug and fails loud inside
// `make_exception_link`.
let llexitcase = link.borrow().llexitcase.clone();
if let Some(case) = llexitcase {
let case_operand = self.getcolor(&case);
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