Function max_depth_bound 

pub fn max_depth_bound(wasm_ops: &[WasmOp]) -> u32

#587: a conservative UPPER BOUND on the wasm value-stack depth this op sequence can reach. Used by the ARM backend’s pool-grow exhaustion- recovery rung to size the i64 spill-slot pool: the number of values simultaneously spilled by the direct selector can never exceed the number of values simultaneously live on the operand stack, so a pool of max_depth_bound slots (plus the resolver/result-parking transients the caller adds) cannot exhaust through the deepest-value spill loop.

Over-approximation rules (never under-counts in reachable code):

• Modeled ops apply their exact pops/pushes; a would-be underflow clamps to 0 (malformed input is someone else’s Err, not a panic here).
• Unmodeled/Bail ops (call, terminators, SIMD, …) are treated as net +1 — every wasm op pushes at most one value net, so this only ever over-counts (a call pops its args; a terminator pushes nothing).
• Block/Loop/If/Else/End are stack-neutral in the effects table, which over-counts (if really pops its condition) — same direction.