[VPlan] Generalize collectUsersInExitBlocks for multiple exit bbs.

Generalize collectUsersInExitBlock to collecting exit users in multiple
exit blocks. Exit blocks are leaf nodes in the VPlan (without
successors) except the scalar header.

Split off from #112138

Author: fhahn

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -8830,12 +8830,12 @@ static void addScalarResumePhis(VPRecipeBuilder &Builder, VPlan &Plan) {
   }
 }
 
-// Collect VPIRInstructions for phis in the original exit block that are modeled
+// Collect VPIRInstructions for phis in the exit blocks that are modeled
 // in VPlan and add the exiting VPValue as operand. Some exiting values are not
 // modeled explicitly yet and won't be included. Those are un-truncated
 // VPWidenIntOrFpInductionRecipe, VPWidenPointerInductionRecipe and induction
 // increments.
-static SetVector<VPIRInstruction *> collectUsersInExitBlock(
+static SetVector<VPIRInstruction *> collectUsersInExitBlocks(
     Loop *OrigLoop, VPRecipeBuilder &Builder, VPlan &Plan,
     const MapVector<PHINode *, InductionDescriptor> &Inductions) {
   SetVector<VPIRInstruction *> ExitUsersToFix;
@@ -8882,8 +8882,8 @@ static SetVector<VPIRInstruction *> collectUsersInExitBlock(
 // Add exit values to \p Plan. Extracts are added for each entry in \p
 // ExitUsersToFix if needed and their operands are updated.
 static void
-addUsersInExitBlock(VPlan &Plan,
-                    const SetVector<VPIRInstruction *> &ExitUsersToFix) {
+addUsersInExitBlocks(VPlan &Plan,
+                     const SetVector<VPIRInstruction *> &ExitUsersToFix) {
   if (ExitUsersToFix.empty())
     return;
 
@@ -9179,12 +9179,11 @@ LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(VFRange &Range) {
     VPlanTransforms::handleUncountableEarlyExit(*Plan, *PSE.getSE(), OrigLoop,
                                                 RecipeBuilder);
   }
-    addScalarResumePhis(RecipeBuilder, *Plan);
-    SetVector<VPIRInstruction *> ExitUsersToFix = collectUsersInExitBlock(
-        OrigLoop, RecipeBuilder, *Plan, Legal->getInductionVars());
-    addExitUsersForFirstOrderRecurrences(*Plan, ExitUsersToFix);
-    addUsersInExitBlock(*Plan, ExitUsersToFix);
-
+  addScalarResumePhis(RecipeBuilder, *Plan);
+  SetVector<VPIRInstruction *> ExitUsersToFix = collectUsersInExitBlocks(
+      OrigLoop, RecipeBuilder, *Plan, Legal->getInductionVars());
+  addExitUsersForFirstOrderRecurrences(*Plan, ExitUsersToFix);
+  addUsersInExitBlocks(*Plan, ExitUsersToFix);
   // ---------------------------------------------------------------------------
   // Transform initial VPlan: Apply previously taken decisions, in order, to
   // bring the VPlan to its final state.