JIT: tighten IV range from "i != bound" assertions in rangecheck#129303
Open
AndyAyersMS wants to merge 1 commit into
Open
JIT: tighten IV range from "i != bound" assertions in rangecheck#129303AndyAyersMS wants to merge 1 commit into
AndyAyersMS wants to merge 1 commit into
Conversation
Follow-on to "JIT: clone i != arr.Length loops to eliminate bounds checks". The cloning change handles NE-loop BCE for loops the cloning heuristic accepts. This change extends NE-loop BCE to cases that fall outside loop cloning (e.g. loops with side-effecting calls in the body that the cloning heuristic rejects). Extend optCreateJTrueBoundsAssertion to create CompareCheckedBound assertions for EQ/NE against a checked bound, and teach RangeCheck::MergeAssertion to tighten ranges using `X != bound` / `X == bound`. For equality assertions where the non-bound side is a constant, defer to the existing LCLVAR-based equality assertion path to preserve downstream consumers that rely on it (e.g. proving `len > 0` after a `len != 0` check). Contributes to dotnet#84697.
github-actions
Bot
added
the
area-CodeGen-coreclr
Member
Author
Contributor
|
Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch |
Contributor
There was a problem hiding this comment.
Pull request overview
This PR extends CoreCLR JIT assertion generation and RangeCheck range-tightening to better exploit loop conditions of the form i != <checked-bound> (e.g., i != arr.Length) by creating/consuming checked-bound equality/inequality assertions to tighten IV ranges and enable more bounds-check elimination outside of loop cloning.
Changes:
- Teach
optCreateJTrueBoundsAssertionto generateCompareCheckedBoundassertions forEQ/NEagainst checked bounds (while deferring checked-bound-vs-constant equalities to existing equality assertion paths). - Extend
RangeCheck::MergeEdgeAssertionsWorkerto tighten ranges usingX != bound(when an existing limit is exactlybound) andX == bound. - Relax debug validation to allow
O2K_VN_ADD_CNSassertions that are equality/inequality (not only ordered relops).
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| src/coreclr/jit/rangecheck.cpp | Tightens IV ranges based on checked-bound ==/!= assertions when limits match the bound. |
| src/coreclr/jit/assertionprop.cpp | Generates checked-bound ==/!= assertions for JTRUE relops and updates debug assertion validation accordingly. |
EgorBo
reviewed
Jun 12, 2026
| // the bound. Tighten: | ||
| // [lo, bound] -> [lo, bound - 1] | ||
| // [bound, hi] -> [bound + 1, hi] | ||
| if (pRange->UpperLimit().IsBinOpArray() && (pRange->UpperLimit().vn == boundVN) && |
Member
There was a problem hiding this comment.
I suspect [bound, ..] assertions aren't useful generally, but it's fine to keep
EgorBo
reviewed
Jun 12, 2026
| // useful than a CompareCheckedBound form -- downstream consumers (folding bounds checks, | ||
| // proving "len > 0" after a "len != 0" test) only recognize the LCLVAR form. Skip the new | ||
| // assertion in that case and let the LCLVAR path produce it. | ||
| if (!(isEqualityRelop && vnStore->IsVNConstant(op2VN))) |
Member
There was a problem hiding this comment.
This can be omitted if AssertionDsc::CreateCompareCheckedBound becomes smarter and switches automatically from O2K_VN_ADD_CNS to O2K_INT_CONST when the vn is a constant
EgorBo
approved these changes
Jun 12, 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
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.
Follow-on to "JIT: clone i != arr.Length loops to eliminate bounds checks". The cloning change handles NE-loop BCE for loops the cloning heuristic accepts. This change extends NE-loop BCE to cases that fall outside loop cloning (e.g. loops with side-effecting calls in the body that the cloning heuristic rejects).
Extend optCreateJTrueBoundsAssertion to create CompareCheckedBound assertions for EQ/NE against a checked bound, and teach RangeCheck::MergeAssertion to tighten ranges using
X != bound/X == bound. For equality assertions where the non-bound side is a constant, defer to the existing LCLVAR-based equality assertion path to preserve downstream consumers that rely on it (e.g. provinglen > 0after alen != 0check).Contributes to #84697.