[compiler] rewrite FreeVariables to not duplicate binding structure #14451
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patrick-schultz
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patrick-schultz
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Apr 9, 2024
| env.getFreeVars | ||
| } | ||
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| assert(old == new_, s"old: $old\nnew: ${new_}\nir:\n${Pretty.sexprStyle(ir, allowUnboundRefs = true)}") |
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Note that all tests passed with this assertion, checking that the new free variables implementation always agrees with the old.
patrick-schultz
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Apr 9, 2024
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| val combEval = Env.fromSeq(IndexedSeq((accumName, {}), (otherAccumName, {}))) | ||
| val combOpFreeVarsCompute = compute(combOp, baseEnv.copy(eval = combEval)) | ||
| val combOpFreeVars = combOpFreeVarsCompute.copy( | ||
| eval = Env.empty[Unit], | ||
| scan = Some(combOpFreeVarsCompute.eval), | ||
| ) | ||
| zeroFreeVars.merge(seqOpFreeVars).merge(combOpFreeVars) | ||
| // the comb op can't refer to anything bound outside, so it can't have free variables | ||
| zeroFreeVars.merge(seqOpFreeVars) |
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The assertion caught one place where the old implementation was wrong: AggFold always added accumName and otherAccumName to the free variables, even though they are never free.
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ehigham
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Apr 9, 2024
ehigham
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Apr 9, 2024
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Before we can simplify the binding structure, we need to stop duplicating it all over the place. This PR rewrites
FreeVariablesso that it no longer needs special logic for particular nodes, hard coding binding structure (redundantly). To do this, it takes advantage of the newBindings, which operates on aGenericBindingEnvinterface. It adds a new implementation of this interface specifically for computing free variables, then simply does a generic traversal of the IR using this custom binging environment.While I find the new implementation far simpler and more obviously correct than the old, I do expect it to further simplify once I'm able to start modifying the core binding structure.