🌐 AI搜索 & 代理 主页
Skip to content

gh-141976: Protect against non-progressing specializations in tracing JIT #141989

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
Fidget-Spinner merged 3 commits into from
Dec 10, 2025
Merged

gh-141976: Protect against non-progressing specializations in tracing JIT #141989

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
5f76e6f
Protect against non-progressing specializations in tracing JIT
Fidget-Spinner Nov 26, 2025
1446220
📜🤖 Added by blurb_it.
blurb-it[bot] Nov 26, 2025
0e949ad
address review
Fidget-Spinner Dec 5, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
1 change: 1 addition & 0 deletions Include/cpython/pystats.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -142,6 +142,7 @@ typedef struct _optimization_stats {
uint64_t recursive_call;
uint64_t low_confidence;
uint64_t unknown_callee;
uint64_t trace_immediately_deopts;
uint64_t executors_invalidated;
UOpStats opcode[PYSTATS_MAX_UOP_ID + 1];
uint64_t unsupported_opcode[256];
Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2025-11-26-20-01-07.gh-issue-141976.K8NDmR.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Protect against specialization failures in the tracing JIT compiler for performance reasons.
19 changes: 19 additions & 0 deletions Python/optimizer.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -610,6 +610,25 @@ _PyJit_translate_single_bytecode_to_trace(
target--;
}

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];
}
}

int old_stack_level = _tstate->jit_tracer_state.prev_state.instr_stacklevel;

// Strange control-flow
Expand Down
Loading