Do not contract control-flow operations during SabreSwap
#13790
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The previous implementation of control-flow handling for `SabreSwap` caused control-flow blocks to contract away from idle qubit wires as a side effect of its algorithm. This will no longer be always valid with the addition of `Box`, and besides, that optimisation isn't part of a routing algorithm's responsibilities, so it's cleaner to have it in a separate pass (now `ContractIdleWiresInControlFlow`) where it can be applied at times other than routing, like in the optimisation loop.
jakelishman
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Changelog: Bugfix
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Pull Request Test Coverage Report for Build 13160002909Warning: This coverage report may be inaccurate.This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.
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Summary
The previous implementation of control-flow handling for
SabreSwapcaused control-flow blocks to contract away from idle qubit wires as a side effect of its algorithm. This will no longer be always valid with the addition ofBox, and besides, that optimisation isn't part of a routing algorithm's responsibilities, so it's cleaner to have it in a separate pass (nowContractIdleWiresInControlFlow) where it can be applied at times other than routing, like in the optimisation loop.Details and comments
Fix #13768.
ContractIdleWiresInControlFlowis in #13779.