feat: add local common subexpression elimination pass#36
Merged
Conversation
Adds `local_cse` as a new post-lowering optimizer pass. Within each basic block, identifies repeated pure computations (BinOp, UnOp, Const) keyed by a hashable ExprKey and replaces subsequent occurrences with the variable from the first occurrence. Requires Hash on BinOp and UnOp, which is added to ir/types.rs. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
This was referenced Mar 27, 2026
arnoox
commented
Mar 27, 2026
arnoox
commented
Mar 27, 2026
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Summary
local_cseas a new post-lowering optimizer passBinOp,UnOp,Const) keyed by a hashableExprKeyand replaces later occurrences with the variable from the firstHashonBinOpandUnOpinir/types.rs(required forExprKey)Pipeline position
Test plan
cargo test -p herkos-core --lib— 208 tests pass (11 new local_cse tests)cargo clippy— cleancargo fmt --checkStack
This is PR F2 of 4 in the optimizer split. Stacked on PR F1 (
pr-f1/branch-fold→ #35).branch_foldlocal_csegvnlicm🤖 Generated with Claude Code