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gh-137838: Fix JIT trace buffer overrun by increasing possible exit stubs #138177

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Merged
merged 8 commits into from
Sep 9, 2025
Merged

gh-137838: Fix JIT trace buffer overrun by increasing possible exit stubs #138177

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gh-137838: Fix JIT trace buffer overrun by increasing possible exit s…
corona10 Aug 27, 2025
650e55d
fix
corona10 Aug 27, 2025
5d816a2
fix
corona10 Aug 27, 2025
b4aad3c
Address code review
corona10 Aug 27, 2025
a6fd711
nit
corona10 Aug 27, 2025
917c6f0
Update
corona10 Aug 28, 2025
57f6c39
Address code review
corona10 Aug 28, 2025
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corona10 Aug 28, 2025
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26 changes: 15 additions & 11 deletions Python/optimizer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -550,7 +550,8 @@ translate_bytecode_to_trace(
_Py_CODEUNIT *instr,
_PyUOpInstruction *trace,
int buffer_size,
_PyBloomFilter *dependencies, bool progress_needed)
_PyBloomFilter *dependencies, bool progress_needed,
bool is_noopt)
{
bool first = true;
PyCodeObject *code = _PyFrame_GetCode(frame);
Expand Down Expand Up @@ -591,7 +592,12 @@ translate_bytecode_to_trace(

for (;;) {
target = INSTR_IP(instr, code);

if (is_noopt) {
max_length-=2;
}
else {
max_length--;
}
uint32_t opcode = instr->op.code;
uint32_t oparg = instr->op.arg;

Expand Down Expand Up @@ -629,8 +635,6 @@ translate_bytecode_to_trace(
assert(opcode != ENTER_EXECUTOR && opcode != EXTENDED_ARG);
RESERVE_RAW(2, "_CHECK_VALIDITY");
ADD_TO_TRACE(_CHECK_VALIDITY, 0, 0, target);
// Need to reserve 1 stub in case the _CHECK_VALIDITY results in a _DEOPT_IF
max_length--;
if (!OPCODE_HAS_NO_SAVE_IP(opcode)) {
RESERVE_RAW(2, "_SET_IP");
ADD_TO_TRACE(_SET_IP, 0, (uintptr_t)instr, target);
Expand All @@ -657,10 +661,6 @@ translate_bytecode_to_trace(
RESERVE_RAW(2, "_ERROR_POP_N");
max_length--;
}
if (OPCODE_HAS_DEOPT(opcode)) {
RESERVE_RAW(2, "_DEOPT");
max_length--;
}
switch (opcode) {
case POP_JUMP_IF_NONE:
case POP_JUMP_IF_NOT_NONE:
Expand Down Expand Up @@ -1287,15 +1287,19 @@ uop_optimize(
_Py_BloomFilter_Init(&dependencies);
_PyUOpInstruction buffer[UOP_MAX_TRACE_LENGTH];
OPT_STAT_INC(attempts);
int length = translate_bytecode_to_trace(frame, instr, buffer, UOP_MAX_TRACE_LENGTH, &dependencies, progress_needed);
char *env_var = Py_GETENV("PYTHON_UOPS_OPTIMIZE");
bool is_noopt = true;
if (env_var == NULL || *env_var == '\0' || *env_var > '0') {
is_noopt = false;
}
Comment on lines +1285 to +1289
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Why was this change made? I think the previous code (without the additional variable) made more sense.

int length = translate_bytecode_to_trace(frame, instr, buffer, UOP_MAX_TRACE_LENGTH, &dependencies, progress_needed, is_noopt);
if (length <= 0) {
// Error or nothing translated
return length;
}
assert(length < UOP_MAX_TRACE_LENGTH);
OPT_STAT_INC(traces_created);
char *env_var = Py_GETENV("PYTHON_UOPS_OPTIMIZE");
if (env_var == NULL || *env_var == '\0' || *env_var > '0') {
if (!is_noopt) {
length = _Py_uop_analyze_and_optimize(frame, buffer,
length,
curr_stackentries, &dependencies);
Expand Down
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