[PATCH] D114586: [VPlan] Verify plan entry and exit blocks, set correct exit block.

[Florian Hahn via Phabricator via llvm-commits]

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

Both the entry and exit blocks of the top-region of a plan must be
VPBasicBlocks. They also must have no predecessors or successors
respectively.

This invariant was broken when splitting a block for sink-after. To fix
the issue, set the exit block of the region *after* sink-after is done.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D114586

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


Index: llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp
+++ llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp
@@ -156,5 +156,25 @@
       RecipeI++;
     }
   }
+
+  const VPRegionBlock *TopRegion = cast<VPRegionBlock>(Plan.getEntry());
+  const VPBasicBlock *Entry = dyn_cast<VPBasicBlock>(TopRegion->getEntry());
+  if (!Entry) {
+    errs() << "VPlan entry block is not a VPBasicBlock\n";
+    return false;
+  }
+  if (Entry->getNumPredecessors() != 0) {
+    errs() << "VPlan entry block has predecessors\n";
+    return false;
+  }
+  const VPBasicBlock *Exit = dyn_cast<VPBasicBlock>(TopRegion->getExit());
+  if (!Exit) {
+    errs() << "VPlan exit block is not a VPBasicBlock\n";
+    return false;
+  }
+  if (Exit->getNumSuccessors() != 0) {
+    errs() << "VPlan exit block has successors\n";
+    return false;
+  }
   return true;
 }
Index: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -9560,7 +9560,6 @@
          !Plan->getEntry()->getEntryBasicBlock()->empty() &&
          "entry block must be set to a VPRegionBlock having a non-empty entry "
          "VPBasicBlock");
-  cast<VPRegionBlock>(Plan->getEntry())->setExit(VPBB);
   RecipeBuilder.fixHeaderPhis();
 
   // ---------------------------------------------------------------------------
@@ -9631,6 +9630,7 @@
     }
   }
 
+  cast<VPRegionBlock>(Plan->getEntry())->setExit(VPBB);
   // Now that sink-after is done, move induction recipes for optimized truncates
   // to the phi section of the header block.
   for (VPWidenIntOrFpInductionRecipe *Ind : InductionsToMove)


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