[llvm] [VPlan] Handle early exit before forming regions. (NFC) (PR #138393)

[via llvm-commits]

================
@@ -2460,64 +2460,63 @@ void VPlanTransforms::convertToConcreteRecipes(VPlan &Plan,
     R->eraseFromParent();
 }
 
-void VPlanTransforms::handleUncountableEarlyExit(
-    VPlan &Plan, Loop *OrigLoop, BasicBlock *UncountableExitingBlock,
-    VPRecipeBuilder &RecipeBuilder, VFRange &Range) {
-  VPRegionBlock *LoopRegion = Plan.getVectorLoopRegion();
-  auto *LatchVPBB = cast<VPBasicBlock>(LoopRegion->getExiting());
-  VPBuilder Builder(LatchVPBB->getTerminator());
-  auto *MiddleVPBB = Plan.getMiddleBlock();
-  VPValue *IsEarlyExitTaken = nullptr;
-
-  // Process the uncountable exiting block. Update IsEarlyExitTaken, which
-  // tracks if the uncountable early exit has been taken. Also split the middle
-  // block and have it conditionally branch to the early exit block if
-  // EarlyExitTaken.
-  auto *EarlyExitingBranch =
-      cast<BranchInst>(UncountableExitingBlock->getTerminator());
-  BasicBlock *TrueSucc = EarlyExitingBranch->getSuccessor(0);
-  BasicBlock *FalseSucc = EarlyExitingBranch->getSuccessor(1);
-  BasicBlock *EarlyExitIRBB =
-      !OrigLoop->contains(TrueSucc) ? TrueSucc : FalseSucc;
-  VPIRBasicBlock *VPEarlyExitBlock = Plan.getExitBlock(EarlyExitIRBB);
-
-  VPValue *EarlyExitNotTakenCond = RecipeBuilder.getBlockInMask(
-      OrigLoop->contains(TrueSucc) ? TrueSucc : FalseSucc);
-  auto *EarlyExitTakenCond = Builder.createNot(EarlyExitNotTakenCond);
-  IsEarlyExitTaken =
-      Builder.createNaryOp(VPInstruction::AnyOf, {EarlyExitTakenCond});
+void VPlanTransforms::handleUncountableEarlyExit(VPBasicBlock *EarlyExitingVPBB,
+                                                 VPBasicBlock *EarlyExitVPBB,
+
+                                                 VPlan &Plan,
+                                                 VPBasicBlock *HeaderVPBB,
+                                                 VPBasicBlock *LatchVPBB,
+                                                 VFRange &Range) {
+  using namespace llvm::VPlanPatternMatch;
 
+  VPBlockBase *MiddleVPBB = LatchVPBB->getSuccessors()[0];
+  if (!EarlyExitVPBB->getSinglePredecessor() &&
+      EarlyExitVPBB->getPredecessors()[0] != MiddleVPBB) {
+    assert(EarlyExitVPBB->getNumPredecessors() == 2 &&
+           EarlyExitVPBB->getPredecessors()[1] == MiddleVPBB &&
+           "unsupported earl exit VPBB");
+    // Early exit operand should always be last phi operand. If EarlyExitVPBB
+    // has two predecessors and MiddleVPBB isn't the first, swap the operands of
+    // the phis.
+    for (VPRecipeBase &R : EarlyExitVPBB->phis())
+      cast<VPIRPhi>(&R)->swapOperands();
+  }
+
+  VPBuilder Builder(LatchVPBB->getTerminator());
+  VPBlockBase *TrueSucc = EarlyExitingVPBB->getSuccessors()[0];
+  assert(
+      match(EarlyExitingVPBB->getTerminator(), m_BranchOnCond(m_VPValue())) &&
+      "Terminator must be be BranchOnCond");
+  VPValue *CondOfEarlyExitingVPBB =
+      EarlyExitingVPBB->getTerminator()->getOperand(0);
+  auto *CondToEarlyExit = TrueSucc == EarlyExitVPBB
+                              ? CondOfEarlyExitingVPBB
+                              : Builder.createNot(CondOfEarlyExitingVPBB);
+  EarlyExitingVPBB->getTerminator()->eraseFromParent();
+  VPBlockUtils::disconnectBlocks(EarlyExitingVPBB, EarlyExitVPBB);
+
----------------
ayalz wrote:

```suggestion
```
Have the caller take care of this, for all early exits consistently?


https://github.com/llvm/llvm-project/pull/138393