This repository has been archived by the owner on Aug 20, 2024. It is now read-only.
Fix RemoveAccesses, delete CSESubAccesses #2157
Merged
Conversation
This file contains 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
jackkoenig
commented
Mar 26, 2021
Comment on lines
+123
to
+142
| // Only called on RefLikes that definitely have a SubAccess | ||
| // Must accept Expression because that's the output type of fixIndices | ||
| def removeSource(e: Expression): Expression = { | ||
| val rs = getLocations(e) | ||
| rs.find(x => x.guard != one) match { | ||
| case None => throwInternalError(s"removeSource: shouldn't be here - $e") | ||
| case Some(_) => | ||
| val (wire, temp) = create_temp(e) | ||
| val temps = create_exps(temp) | ||
| def getTemp(i: Int) = temps(i % temps.size) | ||
| stmts += wire | ||
| rs.zipWithIndex.foreach { | ||
| case (x, i) if i < temps.size => | ||
| stmts += IsInvalid(get_info(s), getTemp(i)) | ||
| stmts += Conditionally(get_info(s), x.guard, Connect(get_info(s), getTemp(i), x.base), EmptyStmt) | ||
| case (x, i) => | ||
| stmts += Conditionally(get_info(s), x.guard, Connect(get_info(s), getTemp(i), x.base), EmptyStmt) | ||
| } | ||
| temp | ||
| } |
There was a problem hiding this comment.
Note this diff is just removing the match since we only ever call this on RefLikeExpressions, the match is redundant.
jackkoenig
commented
Mar 26, 2021
| //case w: WSubIndex => removeSource(w) | ||
| //case w: WSubField => removeSource(w) | ||
| case ref: RefLikeExpression => | ||
| if (hasAccess(ref)) removeSource(fixIndices(ref)) else ref | ||
| case x => x.map(fixSource) |
There was a problem hiding this comment.
The diff above here is the real meat of the PR, by recursing until you see the SubAccess for RHS subaccesses ("Sources"), you end up always expanding the entire aggregate. This changes it to match on the outermost RefLikeExpression it can to ensure that we respect any SubFields or SubIndexes when doing the expansion. This is the fix.
CSESubAccesses was intended to be a simple workaround for a quadratic performance bug in RemoveAccesses but ended up having tricky corner cases and was hard to get right. The solution to the RemoveAccesses bug--quadratic expansion of dynamic indexes of vecs of aggreate type--turned out to be quite simple and makes CSESubAccesses much less useful and not worth fixing.
jackkoenig
force-pushed
the
fix-remove-accesses-perf-bug
branch
from
1a317a3 to
549992e
Compare
azidar
approved these changes
Mar 29, 2021
jackkoenig
added
the
Please Merge
mergify bot
pushed a commit
that referenced
this pull request
Mar 29, 2021
CSESubAccesses was intended to be a simple workaround for a quadratic performance bug in RemoveAccesses but ended up having tricky corner cases and was hard to get right. The solution to the RemoveAccesses bug--quadratic expansion of dynamic indexes of vecs of aggreate type--turned out to be quite simple and makes CSESubAccesses much less useful and not worth fixing. Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com> (cherry picked from commit a41af6f)
mergify
bot
added
the
Backported
mergify bot
added a commit
that referenced
this pull request
Mar 29, 2021
CSESubAccesses was intended to be a simple workaround for a quadratic performance bug in RemoveAccesses but ended up having tricky corner cases and was hard to get right. The solution to the RemoveAccesses bug--quadratic expansion of dynamic indexes of vecs of aggreate type--turned out to be quite simple and makes CSESubAccesses much less useful and not worth fixing. Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com> (cherry picked from commit a41af6f) Co-authored-by: Jack Koenig <[email protected]>
Sign up for free
to subscribe to this conversation on GitHub.
Already have an account?
Sign in.
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.
CSESubAccesses was intended to be a simple workaround for a quadratic
performance bug in RemoveAccesses but ended up having tricky corner
cases and was hard to get right. The solution to the RemoveAccesses
bug--quadratic expansion of dynamic indexes of vecs of aggreate
type--turned out to be quite simple and makes CSESubAccesses much less
useful and not worth fixing.
Note that we didn't really have extensive tests of RemoveAccesses so I just sort of converted the CSESubAccesses tests over to a new RemoveAccessesSpec.
Contributor Checklist
Type of Improvement
API Impact
No impact (CSESubAccesses was never released)
Backend Code Generation Impact
This will likely affect some temporary numbering but should have minimal impact over all.
Desired Merge Strategy
Release Notes
Fix performance bug in RemoveAccesses
Reviewer Checklist (only modified by reviewer)
Please Merge?