[VPlan] Permit derived IV in isHeaderMask#187360
Merged
john-brawn-arm merged 2 commits intollvm:mainfrom Mar 19, 2026
Merged
Conversation
When matching scalar steps of the canonical IV, also match a derived IV of the canonical IV if the derivation is essentially a no-op. Fixes a failure in the mve-reg-pressure-spills.ll test when expensive checks are enabled.
Member
|
@llvm/pr-subscribers-vectorizers @llvm/pr-subscribers-llvm-transforms Author: John Brawn (john-brawn-arm) ChangesWhen matching scalar steps of the canonical IV, also match a derived IV of the canonical IV if the derivation is essentially a no-op. Fixes a failure in the mve-reg-pressure-spills.ll test when expensive checks are enabled. Full diff: https://github.com/llvm/llvm-project/pull/187360.diff 1 Files Affected:
diff --git a/llvm/lib/Transforms/Vectorize/VPlanUtils.cpp b/llvm/lib/Transforms/Vectorize/VPlanUtils.cpp
index ae6fb8e3e9cf5..7921a6fa0411e 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanUtils.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanUtils.cpp
@@ -62,9 +62,10 @@ bool vputils::isHeaderMask(const VPValue *V, const VPlan &Plan) {
VPValue *A, *B;
- auto m_CanonicalScalarIVSteps =
- m_ScalarIVSteps(m_Specific(Plan.getVectorLoopRegion()->getCanonicalIV()),
- m_One(), m_Specific(&Plan.getVF()));
+ auto m_CanonicalScalarIVSteps = m_ScalarIVSteps(
+ m_CombineOr(m_CanonicalIV(),
+ m_DerivedIV(m_ZeroInt(), m_CanonicalIV(), m_One())),
+ m_One(), m_Specific(&Plan.getVF()));
if (match(V, m_ActiveLaneMask(m_VPValue(A), m_VPValue(B), m_One())))
return B == Plan.getTripCount() &&
|
fhahn
reviewed
Mar 18, 2026
Contributor
fhahn
left a comment
fhahn
left a comment
There was a problem hiding this comment.
could you add a test case?
| m_One(), m_Specific(&Plan.getVF())); | ||
| auto m_CanonicalScalarIVSteps = m_ScalarIVSteps( | ||
| m_CombineOr(m_CanonicalIV(), | ||
| m_DerivedIV(m_ZeroInt(), m_CanonicalIV(), m_One())), |
Contributor
There was a problem hiding this comment.
this looks like a missing fold, unless here's a different type?
Collaborator
Author
There was a problem hiding this comment.
Uses of the DerivedIV do get replaced by the CanonicalIV in the simplifyRecipes vplan pass, and the DerivedIV is then removed in removeDeadRecipes, but the vplan verify failure is happening between it being added (by legalizeAndOptimizeInductions) and removed.
Contributor
I think mve-reg-pressure-spills.ll fails without this with EXPENSIVE_CHECKS |
Contributor
Ah right, might be good to pass |
Collaborator
Author
Done |
🐧 Linux x64 Test Results
Failed Tests(click on a test name to see its output) lldb-apilldb-api.functionalities/data-formatter/data-formatter-stl/generic/list/TestDataFormatterGenericList.pyIf these failures are unrelated to your changes (for example tests are broken or flaky at HEAD), please open an issue at https://github.com/llvm/llvm-project/issues and add the |
fhahn
approved these changes
Mar 19, 2026
| m_One(), m_Specific(&Plan.getVF())); | ||
| auto m_CanonicalScalarIVSteps = m_ScalarIVSteps( | ||
| m_CombineOr(m_CanonicalIV(), | ||
| m_DerivedIV(m_ZeroInt(), m_CanonicalIV(), m_One())), |
albertbolt1
pushed a commit
to albertbolt1/llvm-project
that referenced
this pull request
Mar 28, 2026
When matching scalar steps of the canonical IV, also match a derived IV of the canonical IV if the derivation is essentially a no-op. Fixes a failure in the mve-reg-pressure-spills.ll test when expensive checks are enabled.
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
4 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.
When matching scalar steps of the canonical IV, also match a derived IV of the canonical IV if the derivation is essentially a no-op. Fixes a failure in the mve-reg-pressure-spills.ll test when expensive checks are enabled.