[PATCH] D111302: [VPlan] Add initial VPlan verification.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: Ayal, gilr.
Herald added subscribers: tschuett, psnobl, rogfer01, bollu, hiraditya.
fhahn requested review of this revision.
Herald added a subscriber: vkmr.
Herald added a project: LLVM.

This patch adds a function to verify general properties of VPlans. The
first check makes sure that all phi-like recipes are at the beginning of
a block, with no other recipes in between.

Note that this currently may not hold for VPBlendRecipes at the moment,
as other recipes may be inserted before the VPBlendRecipe during mask
creation.

Note that this patch depends on D111300 <https://reviews.llvm.org/D111300> and D111301 <https://reviews.llvm.org/D111301>, which fix code that
breaks the checked invariant.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D111302

Files:
  llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
  llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp
  llvm/lib/Transforms/Vectorize/VPlanVerifier.h


Index: llvm/lib/Transforms/Vectorize/VPlanVerifier.h
===================================================================
--- llvm/lib/Transforms/Vectorize/VPlanVerifier.h
+++ llvm/lib/Transforms/Vectorize/VPlanVerifier.h
@@ -26,6 +26,7 @@
 
 namespace llvm {
 class VPRegionBlock;
+class VPlan;
 
 /// Struct with utility functions that can be used to check the consistency and
 /// invariants of a VPlan, including the components of its H-CFG.
@@ -35,6 +36,12 @@
   /// 1. Region/Block verification: Check the Region/Block verification
   /// invariants for every region in the H-CFG.
   void verifyHierarchicalCFG(const VPRegionBlock *TopRegion) const;
+
+  /// Verify invariants for general VPlans. Currently it checks the following:
+  /// 1. 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.
+  static bool verifyPlanIsValid(const VPlan &Plan);
 };
 } // namespace llvm
 
Index: llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp
+++ llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp
@@ -128,3 +128,28 @@
   assert(!TopRegion->getParent() && "VPlan Top Region should have no parent.");
   verifyRegionRec(TopRegion);
 }
+
+bool VPlanVerifier::verifyPlanIsValid(const VPlan &Plan) {
+  auto Iter = depth_first(
+      VPBlockRecursiveTraversalWrapper<const VPBlockBase *>(Plan.getEntry()));
+  for (const VPBasicBlock *VPBB :
+       VPBlockUtils::blocksOnly<const VPBasicBlock>(Iter)) {
+    // Verify that phi-like recipes are at the beginning of the block, with no
+    // other recipes in between.
+    auto RecipeI = VPBB->begin();
+    auto End = VPBB->end();
+    while (RecipeI != End && RecipeI->isPhi())
+      RecipeI++;
+
+    while (RecipeI != End) {
+      // FIXME: At the moment, creating a mask might insert non-phi recipes
+      // before VPBlendRecipes.
+      if (RecipeI->isPhi() && !isa<VPBlendRecipe>(&*RecipeI)) {
+        errs() << "Found phi-like recipe after non-phi recipes!\n";
+        return false;
+      }
+      RecipeI++;
+    }
+  }
+  return true;
+}
Index: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -9506,6 +9506,7 @@
   RSO.flush();
   Plan->setName(PlanName);
 
+  assert(VPlanVerifier::verifyPlanIsValid(*Plan) && "VPlan is invalid");
   return Plan;
 }
 


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