Deterministic order for CSE parameters based on binding times #4234
+172
−53
Conversation
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
This patch ensures that the `cse_param` variables introduced by the CSE pass are introduced in a stable order that does not depend on the `Int_ids` assigned to variables. This helps making comparisons between different runs (e.g. with different options) using the `flambda2-compare` library. The order is determined lexicographically depending on the primitive under consideration and its arguments, which are guaranteed to be in scope in the target environment (see `cse_with_eligible_lhs`). The order for the argument uses the new `stable_compare_simples` function which is a total order on `Simple.t` values defined in a given typing environment, which coincides with the binding time order and does not depend on `Int_ids` hashing.
lthls
reviewed
Jun 30, 2025
There was a problem hiding this comment.
The PR looks correct, but I'm wondering if you considered having a version of Flambda_primitive.compare that is generic on the simple comparison primitive ?
This would avoid having what is essentially a copy of Flambda_primitive.compare in Common_subexpression_elimination.
|
I got confused by that file, to be honest. Will do. |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
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Outdated suggestions cannot be applied.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.
This patch ensures that the
cse_paramvariables introduced by the CSE pass are introduced in a stable order that does not depend on theInt_idsassigned to variables.This helps making comparisons between different runs (e.g. with different options) using the
flambda2-comparelibrary.The order is determined lexicographically depending on the primitive under consideration and its arguments, which are guaranteed to be in scope in the target environment (see
cse_with_eligible_lhs). The order for the argument uses the newstable_compare_simplesfunction which is a total order onSimple.tvalues defined in a given typing environment, which coincides with the binding time order and does not depend onInt_idshashing.