Keep all Uses in a single vector
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Previously, each live range would carry a list of uses in a `SmallVec<[Use; 4]>`, which was an inefficient use of memory. This PR instead keeps a single `Vec<Use>` for all uses in a function, sorted by vreg and position. Each live range now holds a `Range<u32>` of indices which refer to its uses inside this vector. Benchmarks show that this consistently improves compilation times by ~2%.
Amanieu
commented
Dec 6, 2023
Comment on lines
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| if u.operand.constraint() == OperandConstraint::Any { | ||
| trace!(" -> migrating this any-constrained use to the spill range"); | ||
| spill_uses.push(u); | ||
| // if u.operand.constraint() == OperandConstraint::Any { | ||
| // trace!(" -> migrating this any-constrained use to the spill range"); | ||
| // spill_uses.push(u); | ||
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| // Remember if we're moving the def of this vreg into the spill range, so that | ||
| // we can set the appropriate flags on it later. | ||
| spill_starts_def = spill_starts_def || is_def; | ||
| // // Remember if we're moving the def of this vreg into the spill range, so that | ||
| // // we can set the appropriate flags on it later. | ||
| // spill_starts_def = spill_starts_def || is_def; | ||
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| continue; | ||
| } | ||
| // continue; | ||
| // } |
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This is the only part that I couldn't make work out of the box: since each live range can only refer to a single continuous range of uses, disjoint sets of uses cannot be represented by a single live range.
One option would be to create multiple sub-ranges for the spill bundle here, so that Any uses can still be transferred to the spill bundle.
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Previously, each live range would carry a list of uses in a
SmallVec<[Use; 4]>, which was an inefficient use of memory.This PR instead keeps a single
Vec<Use>for all uses in a function, sorted by vreg and position. Each live range now holds aRange<u32>of indices which refer to its uses inside this vector.Benchmarks show that this consistently improves compilation times by ~2%.