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

[via llvm-commits]

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@@ -3905,22 +3963,27 @@ void VPlanTransforms::handleUncountableEarlyExit(VPBasicBlock *EarlyExitingVPBB,
       ExitIRI->setOperand(EarlyExitIdx, IncomingFromEarlyExit);
     }
   }
-  MiddleBuilder.createNaryOp(VPInstruction::BranchOnCond, {IsEarlyExitTaken});
 
-  // Replace the condition controlling the non-early exit from the vector loop
-  // with one exiting if either the original condition of the vector latch is
-  // true or the early exit has been taken.
+  // Replace the conditional branch controlling the latch exit from the vector
+  // loop with a multi-conditional branch exiting to vector early exit if the
+  // early exit has been taken, exiting to middle block if the original
+  // condition of the vector latch is true, otherwise continuing back to header.
   auto *LatchExitingBranch = cast<VPInstruction>(LatchVPBB->getTerminator());
-  // Skip single-iteration loop region
   assert(LatchExitingBranch->getOpcode() == VPInstruction::BranchOnCount &&
          "Unexpected terminator");
   auto *IsLatchExitTaken =
       Builder.createICmp(CmpInst::ICMP_EQ, LatchExitingBranch->getOperand(0),
                          LatchExitingBranch->getOperand(1));
-  auto *AnyExitTaken = Builder.createNaryOp(
-      Instruction::Or, {IsEarlyExitTaken, IsLatchExitTaken});
-  Builder.createNaryOp(VPInstruction::BranchOnCond, AnyExitTaken);
+
+  DebugLoc LatchDL = LatchExitingBranch->getDebugLoc();
   LatchExitingBranch->eraseFromParent();
+
+  Builder.setInsertPoint(LatchVPBB);
+  Builder.createNaryOp(VPInstruction::BranchOnTwoConds,
+                       {IsEarlyExitTaken, IsLatchExitTaken}, LatchDL);
+  LatchVPBB->clearSuccessors();
+  LatchVPBB->setSuccessors({VectorEarlyExitVPBB, MiddleVPBB, HeaderVPBB});
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ayalz wrote:

Above used a pair of connectSuccessor(), twice. Is this intentional, otherwise better be consistent.

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