HIR passes

These passes operate on qnet modules. Source: include/Dialect/QNet/Passes.td.

qnet-check-linear

A verifier that checks the linear-types invariant of HIR: every !qnet.qubit value must be used at most once. The pass is meant to run before any rewrite that assumes linearity (peephole, dead-code elimination, the HIR-to-MIR lowering, …) — if the invariant is violated, those downstream passes can produce silently wrong IR. The pass has no anchor restriction and no options.

• Pass class: QNetCheckLinear.
• Anchor: any op (no anchor restriction).
• Options: none.

qnet-dead-code-elimination

Quantum dead-code elimination drops quantum dataflow whose effect is not observably used by the classical program. The pass walks backward through the SSA def-use chains from a set of liveness roots (by default, all measurements; with with-classical-awareness=true, only those measurements whose classical outcomes are observably consumed elsewhere) and removes operations that do not contribute to any live qubit value. The full justification — including why a local rotation on the unmeasured side of a (locally or remotely) entangled pair is safe to remove — is given in the accompanying paper.

• Pass class: QNetDeadCodeElimination.
• Anchor: qnet::FuncOp.
• Options:
  • with-classical-awareness: bool (default false) — when true, only treats measurements whose classical results are observably used as liveness roots.

qnet-peephole-optimizations

A family of local rewrites that exploit HIR's value-based semantics: Hermitian self-inverse cancellation, rotation merging, optional Pauli-to-rotation conversion, full-turn elimination, and angle normalization. Hermitian cancellation collapses adjacent same-Hermitian pairs (x x, hadamard hadamard, cnot cnot, …) into the identity. Rotation merging folds two consecutive same-axis rotations into a single one with the summed angle; the float and integer rotation families are handled uniformly, including cross-pattern matches between them. The optional Pauli-to-rotation conversion rewrites qnet.x / qnet.y / qnet.z to their RotX / RotY / RotZ equivalents, exposing further folding opportunities. Full-turn rotations (those whose angle is an integer multiple of 2π, optionally up to a configurable tolerance) are eliminated, and the surviving rotation angles are normalized to the range $[-\pi, \pi]$.

• Pass class: QNetPeepholeOptimizations.
• Anchor: qnet::FuncOp.
• Options:
  • hermitian-cancel: bool (default true) — cancel g g for Hermitian g (x, y, z, hadamard, cnot, cz).
  • rotation-folding: bool (default true) — merge consecutive same-axis rotations into a single rotation.
  • pauli-to-rotations: bool (default false) — convert qnet.x / qnet.y / qnet.z to their rotation-form equivalents.
  • two-pi-epsilon: double (default 0.0) — tolerance for recognizing rotation angles equivalent to multiples of 2π (so the rotation can be removed).
  • normalize-angles: bool (default true) — normalize folded rotation angles to the range $[-\pi, \pi]$.

qnet-show-analysis-gate-count

An analysis-print pass that computes the gate-count analysis on the HIR program and writes the result to the analysis sink (stdout in the default qoala-opt invocation). The pass does not transform the IR; it consults the qoala-opt cost-model flags (single- and two-gate durations — see tools/qoala-opt) when scoring the program.

• Pass class: QNetGateCountShowAnalysis.
• Anchor: mlir::ModuleOp.
• Options: none.