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fix(simulator): avoid zero-length wide scratch arrays in AOT-C emit #3158

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Merged
dalance merged 1 commit into from
Aug 7, 2026
Merged

fix(simulator): avoid zero-length wide scratch arrays in AOT-C emit #3158

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46 changes: 27 additions & 19 deletions crates/simulator/src/backend/aot_c/emit.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -257,6 +257,14 @@ fn wideops_table() -> WideOpsTable {
thread_local! {
static WIDE_TMP_CTR: Cell<usize> = const { Cell::new(0) };
}
/// 64-bit word count for a `native_bytes` size class — the length of the
/// `uint64_t _wN[]` scratch that holds a value of that size. Must round UP:
/// `native_bytes` returns 4 for widths <= 32, and a truncating `/ 8` would
/// declare a zero-length array whose word-0 store is out of bounds.
fn wide_words(nb: usize) -> usize {
nb.div_ceil(8)
}

/// Fresh `_wN` index, unique within a function emit (monotonic; reset by
/// `emit_function` / `emit_event_function` so emitted source is deterministic).
fn next_wide_tmp() -> usize {
Expand Down Expand Up @@ -761,7 +769,7 @@ fn emit_wide_const(
let (width, digits): (usize, Vec<u64>) = match value {
Value::U64(x) if x.width == 0 => {
let target = ctx_width.max(proto_width);
let count = native_bytes(target) / 8;
let count = wide_words(native_bytes(target));
let d = if x.payload != 0 {
vec![u64::MAX; count]
} else {
Expand All @@ -773,7 +781,7 @@ fn emit_wide_const(
Value::BigUint(x) => (proto_width, x.payload.to_u64_digits()),
};
let nb = native_bytes(width);
let nw = nb / 8;
let nw = wide_words(nb);
let t = next_wide_tmp();
let mut init = String::new();
for i in 0..nw {
Expand Down Expand Up @@ -833,7 +841,7 @@ fn emit_wide_expr(expr: &ProtoExpression, pre: &mut String) -> Option<WideRef> {
let idx = emit_expr(&dyn_sel.index_expr)?;
let max_idx = dyn_sel.num_elements - 1;
let src_nb = native_bytes(*var_full_width);
let src_nw = src_nb / 8;
let src_nw = wide_words(src_nb);
let t = next_wide_tmp();
pre.push_str(&format!(
"uint64_t _w{t}[{src_nw}]; \
Expand Down Expand Up @@ -861,7 +869,7 @@ fn emit_wide_expr(expr: &ProtoExpression, pre: &mut String) -> Option<WideRef> {
return None;
}
let src_nb = native_bytes(*var_full_width);
let src_nw = src_nb / 8;
let src_nw = wide_words(src_nb);
let res_nb = native_bytes(nbits);
let t = next_wide_tmp();
pre.push_str(&format!(
Expand Down Expand Up @@ -964,7 +972,7 @@ fn emit_wide_operand(
target_nb: usize,
pre: &mut String,
) -> Option<WideRef> {
let tnw = target_nb / 8;
let tnw = wide_words(target_nb);
// A wide-pointer NODE whose wide emit has no arm may still be scalar-
// emittable when its RESULT is ≤128 bits (e.g. a dynamic select on a
// >128-bit var, which reads a 64..128-bit element into a register):
Expand Down Expand Up @@ -1053,7 +1061,7 @@ fn emit_wide_rhs_field(
return None;
}
let src_nb = native_bytes(src_w);
let src_nw = src_nb / 8;
let src_nw = wide_words(src_nb);
let r = emit_wide_operand(expr, src_nb, pre)?;
let fld = next_wide_tmp();
pre.push_str(&format!(
Expand Down Expand Up @@ -1122,7 +1130,7 @@ fn emit_wide_operand_signed(
let w = expr.width();
if signed && w > 0 && w < target_nb * 8 {
let t = next_wide_tmp();
let tnw = target_nb / 8;
let tnw = wide_words(target_nb);
pre.push_str(&format!(
"uint64_t _w{t}[{tnw}]; vw_sext_copy((uint8_t*)_w{t}, {src}, {w}u, {target_nb}u); ",
src = r.addr,
Expand Down Expand Up @@ -1229,7 +1237,7 @@ fn emit_wide_binary(
let width = expr_context.width;
let result_nb = native_bytes(width);
let op_nb = native_bytes(width.max(x.width()).max(y.width()));
let nw = op_nb / 8;
let nw = wide_words(op_nb);
let mask_pack = wpack(op_nb, width);
match op {
Op::BitAnd | Op::BitOr | Op::BitXor | Op::BitXnor | Op::Add | Op::Sub | Op::Mul => {
Expand Down Expand Up @@ -1307,7 +1315,7 @@ fn emit_wide_binary(
/// mask after the op; identity is unmasked.
fn emit_wide_unary(op: Op, x: &ProtoExpression, width: usize, pre: &mut String) -> Option<WideRef> {
let nb = native_bytes(width);
let nw = nb / 8;
let nw = wide_words(nb);
let x_ref = emit_wide_operand(x, nb, pre)?;
match op {
Op::Add => Some(WideRef {
Expand Down Expand Up @@ -1373,7 +1381,7 @@ fn emit_wide_ternary(
pre: &mut String,
) -> Option<WideRef> {
let nb = native_bytes(width);
let nw = nb / 8;
let nw = wide_words(nb);
let c = emit_expr(cond)?;
let mut t_ref = emit_wide_operand(true_expr, nb, pre)?;
let mut f_ref = emit_wide_operand(false_expr, nb, pre)?;
Expand Down Expand Up @@ -1435,7 +1443,7 @@ fn emit_wide_concat(
pre: &mut String,
) -> Option<WideRef> {
let nb = native_bytes(width);
let nw = nb / 8;
let nw = wide_words(nb);
let acc = next_wide_tmp();
pre.push_str(&format!("uint64_t _w{acc}[{nw}] = {{0}}; "));

Expand Down Expand Up @@ -2283,7 +2291,7 @@ fn emit_event_ff_assign_wide(a: &ProtoAssignStatement) -> Option<String> {
}
let packed = dst_raw == cur_off;
let nb = native_bytes(a.dst_width);
let nw = nb / 8;
let nw = wide_words(nb);
let mut pre = String::new();
// Build the RHS to `nb` bytes, then copy into a fresh scratch and mask it
// there (the canonical FF slot must not be clobbered before commit; the
Expand Down Expand Up @@ -2549,7 +2557,7 @@ fn emit_event_ff_assign_dynamic_wide(a: &ProtoAssignDynamicStatement) -> Option<
return None;
}
let nb = native_bytes(a.dst_width);
let nw = nb / 8;
let nw = wide_words(nb);
let max_idx = a.dst_num_elements.saturating_sub(1);
let idx = emit_expr(&a.dst_index_expr)?;
let mut pre = String::new();
Expand Down Expand Up @@ -3560,7 +3568,7 @@ pub fn emit_stmt(stmt: &ProtoStatement) -> Option<String> {
return None;
}
let nb = native_bytes(a.dst_width);
let nw = nb / 8;
let nw = wide_words(nb);
if win > nb * 8 {
return None;
}
Expand Down Expand Up @@ -3629,7 +3637,7 @@ pub fn emit_stmt(stmt: &ProtoStatement) -> Option<String> {
return None;
}
let nb = native_bytes(a.dst_width);
let nw = nb / 8;
let nw = wide_words(nb);
let dst = format!("(uint8_t*)(comb_values + {store_off:#x})");
let dmask = wpack(nb, a.dst_width);
// Non-foldable rhs_select (rhs isn't a plain variable):
Expand Down Expand Up @@ -4075,7 +4083,7 @@ pub fn emit_stmt(stmt: &ProtoStatement) -> Option<String> {
return None;
}
let nb = native_bytes(a.dst_width);
let nw = nb / 8;
let nw = wide_words(nb);
let max_idx = a.dst_num_elements.saturating_sub(1);
let idx_str = emit_expr(&a.dst_index_expr)?;
let dmask = wpack(nb, a.dst_width);
Expand Down Expand Up @@ -4495,7 +4503,7 @@ fn emit_expr_inner(expr: &ProtoExpression, needs_clean: bool) -> Option<String>
if off < 0 {
return None;
}
let nw = native_bytes(*var_full_width) / 8;
let nw = wide_words(native_bytes(*var_full_width));
let m: u128 = if dyn_sel.window >= 128 {
!0u128
} else {
Expand Down Expand Up @@ -4534,7 +4542,7 @@ fn emit_expr_inner(expr: &ProtoExpression, needs_clean: bool) -> Option<String>
if off < 0 {
return None;
}
let nw = native_bytes(*var_full_width) / 8;
let nw = wide_words(native_bytes(*var_full_width));
return Some(format!(
"({{ uint64_t _idx_raw = (uint64_t)({idx}); \
uint64_t _idx = _idx_raw < {max} ? _idx_raw : {max}; \
Expand Down Expand Up @@ -5281,7 +5289,7 @@ fn emit_expr_inner(expr: &ProtoExpression, needs_clean: bool) -> Option<String>
return None;
}
let src_nb = native_bytes(x_w);
let src_nw = src_nb / 8;
let src_nw = wide_words(src_nb);
let mut pre = String::new();
let xr = emit_wide_operand(x, src_nb, &mut pre)?;
let count = emit_expr(y)?;
Expand Down
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