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Support array repeat expressions (Rvalue::Repeat) #315

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Merged
coord-e merged 1 commit into from
Oct 2, 2026
Merged

Support array repeat expressions (Rvalue::Repeat) #315

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18 changes: 18 additions & 0 deletions src/analyze/basic_block.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -731,6 +731,24 @@ impl<'tcx, 'ctx> Analyzer<'tcx, 'ctx> {
_ => unimplemented!("aggregate kind: {:?}", kind),
}
}
Rvalue::Repeat(operand, count) => {
// TODO: Stop embedding knowledge of `<[T; N] as Model>::Ty` in the analyzer
let count = count
.try_to_target_usize(self.tcx)
.expect("array repeat count must be a known constant");
let mir_elem_ty = operand.ty(&self.body.local_decls, self.tcx);
let elem_ty = self.type_builder.build(mir_elem_ty).vacuous();
let mut builder = PlaceTypeBuilder::default();
let (_, elem_term) = builder.subsume(self.operand_type(operand));
let mut seq = chc::Term::seq_empty(elem_ty.to_sort());
for _ in 0..count {
seq = seq.seq_concat(elem_term.clone().seq_unit());
Comment on lines +744 to +745

@chatgpt-codex-connector chatgpt-codex-connector Bot Sep 30, 2026

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P1 Badge Avoid expanding repeat expressions one element at a time

For valid repeat arrays with counts in the thousands, this loop creates a deeply nested seq.++ term and crashes Thrust before the solver runs. Using the built thrust-rustc, [7i32; 5000] reliably overflowed rustc's stack, while a count of 1000 already produced an 18 MB SMT file. Compact repeat arrays are common for buffers, so the sequence needs a non-linearly nested representation or explicit handling for large counts.

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@coord-e coord-e Oct 2, 2026

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i'm merging this for now and I'll follow-up with another (possible more effective?) option

}
builder.build(
rty::Type::Seq(Box::new(rty::RefinedType::unrefined(elem_ty))),
seq,
)
}
Rvalue::Cast(
mir::CastKind::PointerCoercion(
mir_ty::adjustment::PointerCoercion::ReifyFnPointer,
Expand Down
10 changes: 10 additions & 0 deletions tests/ui/fail/array_repeat.rs
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@@ -0,0 +1,10 @@
//@error-in-other-file: Unsat
//@compile-flags: -C debug-assertions=off
//@rustc-env: THRUST_SOLVER=tests/thrust-pcsat-wrapper

fn main() {
let arr = [7i32; 4];
let s: &[i32] = &arr;
assert!(s.len() == 4);
assert!(s[3] == 8);
}
10 changes: 10 additions & 0 deletions tests/ui/pass/array_repeat.rs
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@@ -0,0 +1,10 @@
//@check-pass
//@compile-flags: -C debug-assertions=off
//@rustc-env: THRUST_SOLVER=tests/thrust-pcsat-wrapper

fn main() {
let arr = [7i32; 4];
let s: &[i32] = &arr;
assert!(s.len() == 4);
assert!(s[3] == 7);
}
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