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GH-113710: Backedge counter improvements. (GH-115166)

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Mark Shannon 2024-02-13 14:16:37 +00:00 • committed by GitHub
parent 7cce857622
commit f9f6156c5a
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7 changed files with 81 additions and 55 deletions
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29
Python/generated_cases.c.h generated
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@ -3263,13 +3263,16 @@
assert(oparg <= INSTR_OFFSET());
JUMPBY(-oparg);
#if ENABLE_SPECIALIZATION
this_instr[1].cache += (1 << OPTIMIZER_BITS_IN_COUNTER);
uint16_t counter = this_instr[1].cache;
this_instr[1].cache = counter + (1 << OPTIMIZER_BITS_IN_COUNTER);
/* We are using unsigned values, but we really want signed values, so
* do the 2s complement comparison manually */
uint16_t ucounter = this_instr[1].cache + (1 << 15);
uint16_t threshold = tstate->interp->optimizer_backedge_threshold + (1 << 15);
* do the 2s complement adjustment manually */
uint32_t offset_counter = counter ^ (1 << 15);
uint32_t threshold = tstate->interp->optimizer_backedge_threshold;
assert((threshold & OPTIMIZER_BITS_MASK) == 0);
// Use '>=' not '>' so that the optimizer/backoff bits do not effect the result.
// Double-check that the opcode isn't instrumented or something:
if (ucounter > threshold && this_instr->op.code == JUMP_BACKWARD) {
if (offset_counter >= threshold && this_instr->op.code == JUMP_BACKWARD) {
OPT_STAT_INC(attempts);
_Py_CODEUNIT *start = this_instr;
/* Back up over EXTENDED_ARGs so optimizer sees the whole instruction */
@ -3283,18 +3286,18 @@
// Rewind and enter the executor:
assert(start->op.code == ENTER_EXECUTOR);
next_instr = start;
this_instr[1].cache &= ((1 << OPTIMIZER_BITS_IN_COUNTER) - 1);
this_instr[1].cache &= OPTIMIZER_BITS_MASK;
}
else {
int backoff = this_instr[1].cache & ((1 << OPTIMIZER_BITS_IN_COUNTER) - 1);
if (backoff < MINIMUM_TIER2_BACKOFF) {
backoff = MINIMUM_TIER2_BACKOFF;
int backoff = this_instr[1].cache & OPTIMIZER_BITS_MASK;
backoff++;
if (backoff < MIN_TIER2_BACKOFF) {
backoff = MIN_TIER2_BACKOFF;
}
else if (backoff < 15 - OPTIMIZER_BITS_IN_COUNTER) {
backoff++;
else if (backoff > MAX_TIER2_BACKOFF) {
backoff = MAX_TIER2_BACKOFF;
}
assert(backoff <= 15 - OPTIMIZER_BITS_IN_COUNTER);
this_instr[1].cache = ((1 << 16) - ((1 << OPTIMIZER_BITS_IN_COUNTER) << backoff)) | backoff;
this_instr[1].cache = ((UINT16_MAX << OPTIMIZER_BITS_IN_COUNTER) << backoff) | backoff;
}
}
#endif /* ENABLE_SPECIALIZATION */