Cranelift: Fold branch-to-trap optimization into the egraphs pass#13688
Merged
cfallin merged 2 commits intoJun 18, 2026
Conversation
The last thing that the legalization pass did was branch-to-trap optimization, where a conditional branch to a block that just unconditionally traps was replaced with a `trapz` or `trapnz`. This commit moves this optimization into the egraph pass via: * Making the branch-to-trap analysis compute its results for a given block on-demand (and memoize its results) so that traversal order doesn't matter. * Adding a `SimplifySkeletonInst::ReplaceWithTwo` variant to replace a skeleton instruction with two other instructions. * Adding two new `simplify_skeleton` ISLE rules that use results from the branch-to-trap analysis and the `ReplaceWithTwo` variant to perform the rewrite. The legalizer and its filetest infrastructure is completely removed.
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
2 participants
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
The last thing that the legalization pass did was branch-to-trap optimization, where a conditional branch to a block that just unconditionally traps was replaced with a
trapzortrapnz. This commit moves this optimization into the egraph pass via:Making the branch-to-trap analysis compute its results for a given block on-demand (and memoize its results) so that traversal order doesn't matter.
Adding a
SimplifySkeletonInst::ReplaceWithTwovariant to replace a skeleton instruction with two other instructions.Adding two new
simplify_skeletonISLE rules that use results from the branch-to-trap analysis and theReplaceWithTwovariant to perform the rewrite.The legalizer and its filetest infrastructure is completely removed.