Redundant stack spills on subsequent escaping calls separated by comments

Bug report

Bug description:

Tier 1 case generator emits stack spill for every subsequent escaping call, when subsequent escaping calls are separated by comment(s). Example:

Subsequent escaping calls without comments in between:

Bytecode definition:

pure inst(NOP, (--)) {
    escaping_call1();
    escaping_call2();
    escaping_call3();
}

Generated case:

TARGET(NOP) {
    frame->instr_ptr = next_instr;
    next_instr += 1;
    INSTRUCTION_STATS(NOP);
    _PyFrame_SetStackPointer(frame, stack_pointer);
    escaping_call1();
    escaping_call2();
    escaping_call3();
    stack_pointer = _PyFrame_GetStackPointer(frame);
    DISPATCH();
}

Subsequent escaping calls with comments in between:

Bytecode definition:

pure inst(NOP, (--)) {
    escaping_call1();
    // comment1
    escaping_call2();
    // comment2
    escaping_call3();
}

Generated case:

TARGET(NOP) {
    frame->instr_ptr = next_instr;
    next_instr += 1;
    INSTRUCTION_STATS(NOP);
    _PyFrame_SetStackPointer(frame, stack_pointer);
    escaping_call1();
    stack_pointer = _PyFrame_GetStackPointer(frame);
    // comment1
    _PyFrame_SetStackPointer(frame, stack_pointer);
    escaping_call2();
    stack_pointer = _PyFrame_GetStackPointer(frame);
    // comment2
    _PyFrame_SetStackPointer(frame, stack_pointer);
    escaping_call3();
    stack_pointer = _PyFrame_GetStackPointer(frame);
    DISPATCH();
}

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-128761

先从报告中展示的 Tier 1 case generator 和 bytecode definition 开始，然后查看链接的 PR gh-128761 以了解当前工作。使用位于 escaping 调用之间的注释重现这些示例，并验证生成的 case 只发出必要的 stack-pointer 操作。