[PATCH] D126679: [VPlan] Update vector latch terminator edge to exit block after execution.

[Florian Hahn via Phabricator via llvm-commits]

fhahn updated this revision to Diff 433103.
fhahn added a comment.

Move code to set branch to ExitBB (aka middle.block) to VPBasicBlock::execute.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D126679/new/

https://reviews.llvm.org/D126679

Files:
  llvm/lib/Transforms/Vectorize/VPlan.cpp


Index: llvm/lib/Transforms/Vectorize/VPlan.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/VPlan.cpp
+++ llvm/lib/Transforms/Vectorize/VPlan.cpp
@@ -274,8 +274,6 @@
       assert(this == LoopRegion->getSingleSuccessor() &&
              "the current block must be the single successor of the region");
       PredBBTerminator->setSuccessor(0, NewBB);
-      PredBBTerminator->setSuccessor(
-          1, CFG.VPBB2IRBB[LoopRegion->getEntryBasicBlock()]);
     }
   }
   return NewBB;
@@ -297,6 +295,13 @@
     // ExitBB can be re-used for the exit block of the Plan.
     NewBB = State->CFG.ExitBB;
     State->CFG.PrevBB = NewBB;
+
+    // Update the branch instruction in the predecessor to branch to ExitBB.
+    VPBlockBase *PredVPBB = getSingleHierarchicalPredecessor();
+    VPBasicBlock *ExitingVPBB = PredVPBB->getExitingBasicBlock();
+    assert(PredVPBB->getSuccessors()[0] == this);
+    BasicBlock *ExitingBB = State->CFG.VPBB2IRBB[ExitingVPBB];
+    cast<BranchInst>(ExitingBB->getTerminator())->setSuccessor(0, NewBB);
   } else if (PrevVPBB && /* A */
              !((SingleHPred = getSingleHierarchicalPredecessor()) &&
                SingleHPred->getExitingBasicBlock() == PrevVPBB &&
@@ -783,11 +788,13 @@
              "empty entry block only expected in VPlanNativePath");
       Header = cast<VPBasicBlock>(Header->getSingleSuccessor());
     }
-    // TODO: Once the exit block is modeled in VPlan, use it instead of going
-    // through State.CFG.ExitBB.
-    BasicBlock *Exit = State.CFG.ExitBB;
 
-    Builder.CreateCondBr(Cond, Exit, State.CFG.VPBB2IRBB[Header]);
+    // Replace the temporary unreachable terminator with a new conditional
+    // branch, hooking it up to backward destination now and to forward
+    // destination(s) later when they are created.
+    BranchInst *CondBr = Builder.CreateCondBr(Cond, Builder.GetInsertBlock(),
+                                              State.CFG.VPBB2IRBB[Header]);
+    CondBr->setSuccessor(0, nullptr);
     Builder.GetInsertBlock()->getTerminator()->eraseFromParent();
     break;
   }


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