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gh-106529: Support JUMP_BACKWARD in Tier 2 (uops) (#106543)

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During superblock generation, a JUMP_BACKWARD instruction is translated to either a JUMP_TO_TOP micro-op (when the target of the jump is exactly the beginning of the superblock, closing the loop), or a SAVE_IP + EXIT_TRACE pair, when the jump goes elsewhere.

The new JUMP_TO_TOP instruction includes a CHECK_EVAL_BREAKER() call, so a closed loop can still be interrupted.
This commit is contained in:
Guido van Rossum 2023-07-11 11:08:10 -07:00 • committed by GitHub
parent 292ac4bfe9
commit cabd6e8a10
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5 changed files with 63 additions and 30 deletions
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15
Python/optimizer.c
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@ -372,9 +372,7 @@ translate_bytecode_to_trace(
_PyUOpInstruction *trace,
int buffer_size)
{
#ifdef Py_DEBUG
_Py_CODEUNIT *initial_instr = instr;
#endif
int trace_length = 0;
int max_length = buffer_size;
@ -456,6 +454,19 @@ translate_bytecode_to_trace(
break;
}
case JUMP_BACKWARD:
{
if (instr + 2 - oparg == initial_instr
&& trace_length + 3 <= max_length)
{
ADD_TO_TRACE(JUMP_TO_TOP, 0);
}
else {
DPRINTF(2, "JUMP_BACKWARD not to top ends trace\n");
}
goto done;
}
default:
{
const struct opcode_macro_expansion *expansion = &_PyOpcode_macro_expansion[opcode];