[llvm] [VPlan] Add BranchOnMultiCond, use for early exit plans. (PR #172750)

[Florian Hahn via llvm-commits]

================
@@ -3846,36 +3900,36 @@ void VPlanTransforms::handleUncountableEarlyExit(VPBasicBlock *EarlyExitingVPBB,
                               ? CondOfEarlyExitingVPBB
                               : Builder.createNot(CondOfEarlyExitingVPBB);
 
-  // Split the middle block and have it conditionally branch to the early exit
-  // block if CondToEarlyExit.
+  // Create a BranchOnMultiCond in the latch that branches to:
+  // [0] vector.early.exit, [1] middle block, [2] header (continue looping).
   VPValue *IsEarlyExitTaken =
       Builder.createNaryOp(VPInstruction::AnyOf, {CondToEarlyExit});
-  VPBasicBlock *NewMiddle = Plan.createVPBasicBlock("middle.split");
   VPBasicBlock *VectorEarlyExitVPBB =
       Plan.createVPBasicBlock("vector.early.exit");
-  VPBlockUtils::insertOnEdge(LatchVPBB, MiddleVPBB, NewMiddle);
-  VPBlockUtils::connectBlocks(NewMiddle, VectorEarlyExitVPBB);
-  NewMiddle->swapSuccessors();
+  VectorEarlyExitVPBB->setParent(LatchVPBB->getParent());
 
+  // Update PHI operands: copy from EarlyExitingVPBB to VectorEarlyExitVPBB.
+  unsigned PredIdx = EarlyExitVPBB->getIndexForPredecessor(EarlyExitingVPBB);
   VPBlockUtils::connectBlocks(VectorEarlyExitVPBB, EarlyExitVPBB);
 
-  // Update the exit phis in the early exit block.
-  VPBuilder MiddleBuilder(NewMiddle);
   VPBuilder EarlyExitB(VectorEarlyExitVPBB);
+  VPBuilder MiddleBuilder(cast<VPBasicBlock>(MiddleVPBB));
----------------
fhahn wrote:

done thanks

https://github.com/llvm/llvm-project/pull/172750