[llvm] [VPlan] Dispatch to multiple exit blocks via middle blocks. (PR #112138)

[Florian Hahn via llvm-commits]

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@@ -1796,3 +1802,57 @@ void VPlanTransforms::createInterleaveGroups(
       }
   }
 }
+
+void VPlanTransforms::handleUncountableEarlyExit(
+    VPlan &Plan, ScalarEvolution &SE, Loop *OrigLoop,
+    ArrayRef<BasicBlock *> UncountableExitingBlocks,
+    VPRecipeBuilder &RecipeBuilder) {
+  auto *LatchVPBB =
+      cast<VPBasicBlock>(Plan.getVectorLoopRegion()->getExiting());
+  VPBuilder Builder(LatchVPBB->getTerminator());
+  auto *MiddleVPBB = Plan.getMiddleBlock();
+  VPRegionBlock *LoopRegion = Plan.getVectorLoopRegion();
+  VPValue *EarlyExitTaken = nullptr;
+
+  // Process all uncountable exiting blocks. For each exiting block, update the
+  // EarlyExitTaken, which tracks if any uncountable early exit has been taken.
+  // Also split the middle block and branch to the exit block for the early exit
+  // if it has been taken.
+  for (BasicBlock *Exiting : UncountableExitingBlocks) {
+    auto *ExitingTerm = cast<BranchInst>(Exiting->getTerminator());
+    BasicBlock *TrueSucc = ExitingTerm->getSuccessor(0);
+    BasicBlock *FalseSucc = ExitingTerm->getSuccessor(1);
+    VPIRBasicBlock *VPExitBlock;
+    if (OrigLoop->getUniqueExitBlock()) {
+      VPExitBlock = cast<VPIRBasicBlock>(MiddleVPBB->getSuccessors()[0]);
+    } else {
+      VPExitBlock = VPIRBasicBlock::fromBasicBlock(
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fhahn wrote:

I think `UncountableExitingBlocks` should only have a single exiting block at the moment, updated to process only a single one for now

https://github.com/llvm/llvm-project/pull/112138