[llvm] [VPlan] Generalize collectUsersInExitBlocks for multiple exit bbs. (PR #115066)

[Florian Hahn via llvm-commits]

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@@ -306,6 +306,15 @@ template <> struct GraphTraits<VPlan *> {
   }
 };
 
+inline auto VPlan::getExitBlocks() {
+  VPBlockBase *ScalarHeader = getScalarHeader();
+  return make_filter_range(
+      VPBlockUtils::blocksOnly<VPIRBasicBlock>(
+          vp_depth_first_shallow(getVectorLoopRegion()->getSingleSuccessor())),
+      [ScalarHeader](VPIRBasicBlock *VPIRBB) {
+        return VPIRBB != ScalarHeader && VPIRBB->getNumSuccessors() == 0;
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fhahn wrote:

It should always return the exit blocks currently in the VPlan, so if some transformation replaces/removes some of the exit blocks, the result would be different. But at the moment, the exit blocks should be fixed, we know them at time of construction and can wrap them in VPIRBasicBlocks and those shouldn't change (and if they change the transform would be responsible to make sure the exit phis are updated accordingly).

Is there anything particular in VPlan::execute you are thinking of? (We replace VPBasicBlocks with VPIRBasicBlocks in some cases if they are only created during skeleton creation, but that shouldn't be the case for the exit blocks)

https://github.com/llvm/llvm-project/pull/115066