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Use stack_effect_info for getting pop&push count #6913

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Merged
youknowone merged 3 commits into from
Jan 31, 2026
Merged

Use stack_effect_info for getting pop&push count #6913

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39dff7a
Use `stack_effect_info` for getting pop&push count
ShaharNaveh Jan 31, 2026
79c8872
Merge remote-tracking branch 'upstream/main' into after-split-cleanup
ShaharNaveh Jan 31, 2026
f3a527a
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ShaharNaveh Jan 31, 2026
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Use stack_effect_info for getting pop&push count
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@ShaharNaveh
ShaharNaveh committed Jan 31, 2026
commit 39dff7a7fa79ca94b1ee4062a1daded25b0b4f53
60 changes: 3 additions & 57 deletions crates/codegen/src/ir.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -713,7 +713,7 @@ impl CodeInfo {
// (or NOT_LOCAL if not from LOAD_FAST/LOAD_FAST_LOAD_FAST).
//
// CPython (flowgraph.c optimize_load_fast) pre-fills the stack with
// dummy refs for values inherited from predecessor blocks. We take
// dummy refs for values inherited from predecessor blocks. We take
// the simpler approach of aborting the optimisation for the whole
// block on stack underflow.
let mut stack: Vec<usize> = Vec::new();
Expand All @@ -724,62 +724,8 @@ impl CodeInfo {
continue;
};

// Decompose into (pops, pushes).
//
// stack_effect() returns pushes − pops, which is ambiguous for
// instructions that both pop and push (e.g. BinaryOp: effect=-1
// is pop 2 push 1, not pop 1 push 0). We list those explicitly;
// the fallback under-pops and under-pushes, which is conservative
// (may miss optimisation opportunities but never miscompiles).
let effect = instr.stack_effect(info.arg.into());
let (pops, pushes) = match instr {
// --- pop 2, push 1 ---
Instruction::BinaryOp { .. }
| Instruction::BinaryOpInplaceAddUnicode
| Instruction::CompareOp { .. }
| Instruction::ContainsOp(_)
| Instruction::IsOp(_)
| Instruction::ImportName { .. }
| Instruction::FormatWithSpec => (2, 1),

// --- pop 1, push 1 ---
Instruction::UnaryInvert
| Instruction::UnaryNegative
| Instruction::UnaryNot
| Instruction::ToBool
| Instruction::GetIter
| Instruction::GetAIter
| Instruction::FormatSimple
| Instruction::LoadFromDictOrDeref(_)
| Instruction::LoadFromDictOrGlobals(_) => (1, 1),

// LoadAttr: pop receiver, push attr.
// method=true: push (method, self_or_null) → (1, 2)
Instruction::LoadAttr { idx } => {
let (_, is_method) =
rustpython_compiler_core::bytecode::decode_load_attr_arg(
idx.get(info.arg),
);
if is_method { (1, 2) } else { (1, 1) }
}

// --- pop 3, push 1 ---
Instruction::BinarySlice => (3, 1),

// --- variable pops, push 1 ---
Instruction::Call { nargs } => (nargs.get(info.arg) as usize + 2, 1),
Instruction::CallKw { nargs } => (nargs.get(info.arg) as usize + 3, 1),

// --- conservative fallback ---
// under-pops (≤ actual pops) and under-pushes (≤ actual pushes),
// which keeps extra refs on the stack → marks them unconsumed →
// prevents optimisation. Safe but may miss opportunities.
_ => {
let p = if effect < 0 { (-effect) as usize } else { 0 };
let q = if effect > 0 { effect as usize } else { 0 };
(p, q)
}
};
let stack_effect_info = instr.stack_effect_info(info.arg.into());
let (pushes, pops) = (stack_effect_info.pushed(), stack_effect_info.popped());

// Pop values from stack
for _ in 0..pops {
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