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[AutoDiff] Mark rsqrt as non-linear for adstack promotion #499

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Merged
duburcqa merged 1 commit into from
Apr 17, 2026
Merged

[AutoDiff] Mark rsqrt as non-linear for adstack promotion #499

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4 changes: 2 additions & 2 deletions quadrants/transforms/auto_diff.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -41,12 +41,12 @@
class NonLinearOps {
public:
inline static const std::set<TernaryOpType> ternary_collections{TernaryOpType::select};
inline static const std::set<UnaryOpType> unary_collections{
UnaryOpType::abs, UnaryOpType::sin, UnaryOpType::cos, UnaryOpType::tan, UnaryOpType::tanh,
UnaryOpType::asin, UnaryOpType::acos, UnaryOpType::exp, UnaryOpType::log, UnaryOpType::sqrt};
UnaryOpType::abs, UnaryOpType::sin, UnaryOpType::cos, UnaryOpType::tan, UnaryOpType::tanh, UnaryOpType::asin,
UnaryOpType::acos, UnaryOpType::exp, UnaryOpType::log, UnaryOpType::sqrt, UnaryOpType::rsqrt};
inline static const std::set<BinaryOpType> binary_collections{BinaryOpType::mul, BinaryOpType::div,
BinaryOpType::atan2, BinaryOpType::pow};
};

Check notice on line 49 in quadrants/transforms/auto_diff.cpp

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Claude / Claude Code Review

AdStackAllocaJudger only traces first LocalLoad: multi-load alloca not promoted for rsqrt 

The `AdStackAllocaJudger::visit(LocalLoadStmt*)` method updates `target_alloca_` to the FIRST `LocalLoadStmt` it encounters, so any subsequent `LocalLoad` from the same alloca (where `stmt->src == original_alloca \!= target_alloca_`) is silently ignored; if only the second load feeds a nonlinear op like `rsqrt`, `is_stack_needed_` stays false and the alloca is not promoted to AdStack. This is a pre-existing limitation that affects all ops in `NonLinearOps::unary_collections` equally — the PR cor

class IndependentBlocksJudger : public BasicStmtVisitor {
public:
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1 change: 1 addition & 0 deletions tests/python/test_adstack.py
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@
(qd.sqrt, "sqrt"),
(qd.tanh, "tanh"),
(qd.exp, "exp"),
(qd.rsqrt, "rsqrt"),
],
)
@test_utils.test(require=qd.extension.adstack, ad_stack_experimental_enabled=True)
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