[llvm] [VPlan] Assert vplan-verify-each result and get verifier passing (PR #182254)
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Thu Feb 19 04:22:30 PST 2026
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-vectorizers
Author: Luke Lau (lukel97)
<details>
<summary>Changes</summary>
Currently if -vplan-verify-each is enabled and a pass fails the verifier, it will output the failure to stderr but will still finish with a zero exit code.
This adds an assert that the verification fails so that e.g. lit will pick up verifier failures in the in-tree tests with an EXPENSIVE_CHECKS build. However currently the verifier fails in several tests, so this also includes several fixes:
1. Remove the EVL verifier checks. The EVL is used in quite a few more places than when the verification was originally added, and nowadays it gets used in a variety of VPInstructions, all of which need to be handled by the verifier. There are a few passes that fail today because we haven't updated the EVL verification. Now that the EVL transform has been split up into a variable stepping transform and an optimization pass it's generally less fragile, so there is less value in this verification.
2. Extend the LastActiveLane verification to handle more prefix masks. All of the prefix masks that the verifier encounters are of the form `icmp ult/ule monotonically-increasing-sequence, uniform`, which always generate a prefix mask.
3. Allow multiple VPActiveLaneMaskPHIRecipe recipes after unrolling. This also allows us to remove the verifyLate argument
Tested that llvm-test-suite + SPEC CPU 2017 now pass with -vplan-verify-each enabled for RISC-V.
---
Full diff: https://github.com/llvm/llvm-project/pull/182254.diff
4 Files Affected:
- (modified) llvm/lib/Transforms/Vectorize/LoopVectorize.cpp (+2-3)
- (modified) llvm/lib/Transforms/Vectorize/VPlanTransforms.h (+4-2)
- (modified) llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp (+26-125)
- (modified) llvm/lib/Transforms/Vectorize/VPlanVerifier.h (+2-4)
``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 01433fe4c4ba7..68bdb9f4ba23f 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -364,7 +364,7 @@ cl::opt<bool>
cl::init(false),
#endif
cl::Hidden,
- cl::desc("Verfiy VPlans after VPlan transforms."));
+ cl::desc("Verify VPlans after VPlan transforms."));
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
cl::opt<bool> llvm::VPlanPrintAfterAll(
@@ -7512,8 +7512,7 @@ DenseMap<const SCEV *, Value *> LoopVectorizationPlanner::executePlan(
State.CFG.PrevBB->getSingleSuccessor(), &BestVPlan);
VPlanTransforms::removeDeadRecipes(BestVPlan);
- assert(verifyVPlanIsValid(BestVPlan, true /*VerifyLate*/) &&
- "final VPlan is invalid");
+ assert(verifyVPlanIsValid(BestVPlan) && "final VPlan is invalid");
// After vectorization, the exit blocks of the original loop will have
// additional predecessors. Invalidate SCEVs for the exit phis in case SE
diff --git a/llvm/lib/Transforms/Vectorize/VPlanTransforms.h b/llvm/lib/Transforms/Vectorize/VPlanTransforms.h
index f2dfc166cecc9..e35872bbdff37 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanTransforms.h
+++ b/llvm/lib/Transforms/Vectorize/VPlanTransforms.h
@@ -72,8 +72,10 @@ struct VPlanTransforms {
dbgs() << Plan << '\n';
}
#endif
- if (VerifyEachVPlan && EnableVerify)
- verifyVPlanIsValid(Plan);
+ if (VerifyEachVPlan && EnableVerify) {
+ [[maybe_unused]] bool IsValid = verifyVPlanIsValid(Plan);
+ assert(IsValid && "VPlan is invalid");
+ }
}};
return std::forward<PassTy>(Pass)(Plan, std::forward<ArgsTy>(Args)...);
diff --git a/llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp b/llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp
index e4b334c3eba49..2db7287d494f6 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp
@@ -31,7 +31,6 @@ namespace {
class VPlanVerifier {
const VPDominatorTree &VPDT;
VPTypeAnalysis &TypeInfo;
- bool VerifyLate;
SmallPtrSet<BasicBlock *, 8> WrappedIRBBs;
@@ -40,11 +39,6 @@ class VPlanVerifier {
// VPHeaderPHIRecipes.
bool verifyPhiRecipes(const VPBasicBlock *VPBB);
- /// Verify that \p EVL is used correctly. The user must be either in
- /// EVL-based recipes as a last operand or VPInstruction::Add which is
- /// incoming value into EVL's recipe.
- bool verifyEVLRecipe(const VPInstruction &EVL) const;
-
/// Verify that \p LastActiveLane's operand is guaranteed to be a prefix-mask.
bool verifyLastActiveLaneRecipe(const VPInstruction &LastActiveLane) const;
@@ -67,9 +61,8 @@ class VPlanVerifier {
bool verifyRegionRec(const VPRegionBlock *Region);
public:
- VPlanVerifier(VPDominatorTree &VPDT, VPTypeAnalysis &TypeInfo,
- bool VerifyLate)
- : VPDT(VPDT), TypeInfo(TypeInfo), VerifyLate(VerifyLate) {}
+ VPlanVerifier(VPDominatorTree &VPDT, VPTypeAnalysis &TypeInfo)
+ : VPDT(VPDT), TypeInfo(TypeInfo) {}
bool verify(const VPlan &Plan);
};
@@ -124,7 +117,7 @@ bool VPlanVerifier::verifyPhiRecipes(const VPBasicBlock *VPBB) {
RecipeI++;
}
- if (!VerifyLate && NumActiveLaneMaskPhiRecipes > 1) {
+ if (!VPBB->getPlan()->isUnrolled() && NumActiveLaneMaskPhiRecipes > 1) {
errs() << "There should be no more than one VPActiveLaneMaskPHIRecipe";
return false;
}
@@ -146,106 +139,19 @@ bool VPlanVerifier::verifyPhiRecipes(const VPBasicBlock *VPBB) {
return true;
}
-bool VPlanVerifier::verifyEVLRecipe(const VPInstruction &EVL) const {
- if (EVL.getOpcode() != VPInstruction::ExplicitVectorLength) {
- errs() << "verifyEVLRecipe should only be called on "
- "VPInstruction::ExplicitVectorLength\n";
- return false;
- }
- auto VerifyEVLUse = [&](const VPRecipeBase &R,
- const unsigned ExpectedIdx) -> bool {
- SmallVector<const VPValue *> Ops(R.operands());
- unsigned UseCount = count(Ops, &EVL);
- if (UseCount != 1 || Ops[ExpectedIdx] != &EVL) {
- errs() << "EVL is used as non-last operand in EVL-based recipe\n";
- return false;
- }
+static bool isKnownMonotonic(VPValue *V) {
+ VPValue *X, *Y;
+ if (match(V, m_Add(m_VPValue(X), m_VPValue(Y))))
+ return isKnownMonotonic(X) && isKnownMonotonic(Y);
+ if (match(V, m_StepVector()))
return true;
- };
- auto VerifyEVLUseInVecEndPtr = [&EVL](auto &VEPRs) {
- if (all_of(VEPRs, [&EVL](VPUser *U) {
- auto *VEPR = cast<VPVectorEndPointerRecipe>(U);
- return match(VEPR->getOffset(),
- m_c_Mul(m_SpecificSInt(VEPR->getStride()),
- m_Sub(m_Specific(&EVL), m_One())));
- }))
- return true;
- errs() << "Expected VectorEndPointer with EVL operand\n";
- return false;
- };
- return all_of(EVL.users(), [&](VPUser *U) {
- return TypeSwitch<const VPUser *, bool>(U)
- .Case([&](const VPWidenIntrinsicRecipe *S) {
- return VerifyEVLUse(*S, S->getNumOperands() - 1);
- })
- .Case<VPWidenStoreEVLRecipe, VPReductionEVLRecipe,
- VPWidenIntOrFpInductionRecipe, VPWidenPointerInductionRecipe>(
- [&](const VPRecipeBase *S) { return VerifyEVLUse(*S, 2); })
- .Case([&](const VPScalarIVStepsRecipe *R) {
- if (R->getNumOperands() != 3) {
- errs() << "Unrolling with EVL tail folding not yet supported\n";
- return false;
- }
- return VerifyEVLUse(*R, 2);
- })
- .Case<VPWidenLoadEVLRecipe, VPVectorEndPointerRecipe,
- VPInterleaveEVLRecipe>(
- [&](const VPRecipeBase *R) { return VerifyEVLUse(*R, 1); })
- .Case(
- [&](const VPInstructionWithType *S) { return VerifyEVLUse(*S, 0); })
- .Case([&](const VPInstruction *I) {
- if (I->getOpcode() == Instruction::PHI ||
- I->getOpcode() == Instruction::ICmp)
- return VerifyEVLUse(*I, 1);
- if (I->getOpcode() == Instruction::Sub) {
- // If Sub has a single user that's a SingleDefRecipe (which is
- // expected to be a Mul), filter its users, in turn, to get
- // VectorEndPointerRecipes, and verify that all the offsets match
- // (EVL - 1) * Stride.
- if (auto *Def = dyn_cast_if_present<VPSingleDefRecipe>(
- I->getSingleUser())) {
- auto VEPRs = make_filter_range(Def->users(),
- IsaPred<VPVectorEndPointerRecipe>);
- if (!VEPRs.empty())
- return VerifyEVLUseInVecEndPtr(VEPRs);
- }
- return VerifyEVLUse(*I, 1);
- }
- switch (I->getOpcode()) {
- case Instruction::Add:
- break;
- case Instruction::UIToFP:
- case Instruction::Trunc:
- case Instruction::ZExt:
- case Instruction::Mul:
- case Instruction::Shl:
- case Instruction::FMul:
- case VPInstruction::Broadcast:
- case VPInstruction::PtrAdd:
- // Opcodes above can only use EVL after wide inductions have been
- // expanded.
- if (!VerifyLate) {
- errs() << "EVL used by unexpected VPInstruction\n";
- return false;
- }
- break;
- default:
- errs() << "EVL used by unexpected VPInstruction\n";
- return false;
- }
- if (!VerifyLate &&
- !isa<VPCurrentIterationPHIRecipe>(*I->users().begin())) {
- errs() << "Result of VPInstruction::Add with EVL operand is "
- "not used by VPCurrentIterationPHIRecipe\n";
- return false;
- }
- return true;
- })
- .Default([&](const VPUser *U) {
- errs() << "EVL has unexpected user\n";
- return false;
- });
- });
+ if (auto *WidenIV = dyn_cast<VPWidenIntOrFpInductionRecipe>(V))
+ return match(WidenIV->getStepValue(), m_One());
+ if (auto *WidenIV = dyn_cast<VPScalarIVStepsRecipe>(V))
+ return match(WidenIV->getStepValue(), m_One());
+ if (isa<VPWidenCanonicalIVRecipe>(V))
+ return true;
+ return vputils::isUniformAcrossVFsAndUFs(V);
}
bool VPlanVerifier::verifyLastActiveLaneRecipe(
@@ -259,18 +165,19 @@ bool VPlanVerifier::verifyLastActiveLaneRecipe(
}
const VPlan &Plan = *LastActiveLane.getParent()->getPlan();
- // All operands must be prefix-mask. Currently we check for header masks or
- // EVL-derived masks, as those are currently the only operands in practice,
- // but this may need updating in the future.
+ // All operands must be prefix-mask. This means an icmp ult/ule LHS, RHS where
+ // the LHS is monotonically increasing and RHS is uniform.
for (VPValue *Op : LastActiveLane.operands()) {
if (vputils::isHeaderMask(Op, Plan))
continue;
- // Masks derived from EVL are also fine.
- auto BroadcastOrEVL =
- m_CombineOr(m_Broadcast(m_EVL(m_VPValue())), m_EVL(m_VPValue()));
- if (match(Op, m_CombineOr(m_ICmp(m_StepVector(), BroadcastOrEVL),
- m_ICmp(BroadcastOrEVL, m_StepVector()))))
+ CmpPredicate Pred;
+ VPValue *LHS, *RHS;
+ if (match(Op, m_ICmp(Pred, m_VPValue(LHS), m_VPValue(RHS))) &&
+ (Pred == CmpInst::ICMP_ULE || Pred == CmpInst::ICMP_ULT) &&
+ isKnownMonotonic(LHS) &&
+ (vputils::isUniformAcrossVFsAndUFs(RHS) ||
+ vputils::isSingleScalar(RHS)))
continue;
errs() << "LastActiveLane operand ";
@@ -372,12 +279,6 @@ bool VPlanVerifier::verifyVPBasicBlock(const VPBasicBlock *VPBB) {
}
if (const auto *VPI = dyn_cast<VPInstruction>(&R)) {
switch (VPI->getOpcode()) {
- case VPInstruction::ExplicitVectorLength:
- if (!verifyEVLRecipe(*VPI)) {
- errs() << "EVL VPValue is not used correctly\n";
- return false;
- }
- break;
case VPInstruction::LastActiveLane:
if (!verifyLastActiveLaneRecipe(*VPI))
return false;
@@ -569,9 +470,9 @@ bool VPlanVerifier::verify(const VPlan &Plan) {
return true;
}
-bool llvm::verifyVPlanIsValid(const VPlan &Plan, bool VerifyLate) {
+bool llvm::verifyVPlanIsValid(const VPlan &Plan) {
VPDominatorTree VPDT(const_cast<VPlan &>(Plan));
VPTypeAnalysis TypeInfo(Plan);
- VPlanVerifier Verifier(VPDT, TypeInfo, VerifyLate);
+ VPlanVerifier Verifier(VPDT, TypeInfo);
return Verifier.verify(Plan);
}
diff --git a/llvm/lib/Transforms/Vectorize/VPlanVerifier.h b/llvm/lib/Transforms/Vectorize/VPlanVerifier.h
index ccf79e8e5c985..642b25b0635c0 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanVerifier.h
+++ b/llvm/lib/Transforms/Vectorize/VPlanVerifier.h
@@ -29,16 +29,14 @@
namespace llvm {
class VPlan;
-/// Verify invariants for general VPlans. If \p VerifyLate is passed, skip some
-/// checks that are not applicable at later stages of the transform pipeline.
+/// Verify invariants for general VPlans.
/// Currently it checks the following:
/// 1. Region/Block verification: Check the Region/Block verification
/// invariants for every region in the H-CFG.
/// 2. all phi-like recipes must be at the beginning of a block, with no other
/// recipes in between. Note that currently there is still an exception for
/// VPBlendRecipes.
-LLVM_ABI_FOR_TEST bool verifyVPlanIsValid(const VPlan &Plan,
- bool VerifyLate = false);
+LLVM_ABI_FOR_TEST bool verifyVPlanIsValid(const VPlan &Plan);
} // namespace llvm
``````````
</details>
https://github.com/llvm/llvm-project/pull/182254
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