Protect against specialization failures in the tracing JIT compiler for performance reasons.

if (_PyOpcode_Caches[_PyOpcode_Deopt[opcode]] > 0) {

uint16_t backoff = (this_instr + 1)->counter.value_and_backoff;

// adaptive_counter_cooldown is a fresh specialization.

// trigger_backoff_counter is what we set during tracing.

// All tracing backoffs should be freshly specialized or untouched.

// If not, that indicates a deopt during tracing, and

// thus the "actual" instruction executed is not the one that is

// in the instruction stream, but rather the deopt.

// It's important we check for this, as some specializations might make

// no progress (they can immediately deopt after specializing).

// We do this to improve performance, as otherwise a compiled trace

// will just deopt immediately.

if (backoff != adaptive_counter_cooldown().value_and_backoff &&

backoff != trigger_backoff_counter().value_and_backoff) {

OPT_STAT_INC(trace_immediately_deopts);

opcode = _PyOpcode_Deopt[opcode];

}

}