[llvm] [VPlan] Build initial VPlan 0 using HCFGBuilder for inner loops. (NFC) (PR #124432)

[via llvm-commits]

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@@ -9312,23 +9317,45 @@ LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(VFRange &Range) {
   RecipeBuilder.collectScaledReductions(Range);
 
   auto *MiddleVPBB = Plan->getMiddleBlock();
+  ReversePostOrderTraversal<VPBlockShallowTraversalWrapper<VPBlockBase *>> RPOT(
+      Plan->getVectorLoopRegion()->getEntry());
+
   VPBasicBlock::iterator MBIP = MiddleVPBB->getFirstNonPhi();
-  for (BasicBlock *BB : make_range(DFS.beginRPO(), DFS.endRPO())) {
-    // Relevant instructions from basic block BB will be grouped into VPRecipe
-    // ingredients and fill a new VPBasicBlock.
-    if (VPBB != HeaderVPBB)
-      VPBB->setName(BB->getName());
-    Builder.setInsertPoint(VPBB);
+  VPBlockBase *PrevVPBB = nullptr;
+  for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(RPOT)) {
+    // Skip VPBBs not corresponding to any input IR basic blocks.
+    if (!HCFGBuilder.getIRBBForVPB(VPBB))
+      continue;
 
-    if (VPBB == HeaderVPBB)
+    // Create mask based on the IR BB corresponding to VPBB.
+    // TODO: Predicate directly based on VPlan.
+    if (VPBB == HeaderVPBB) {
+      Builder.setInsertPoint(VPBB, VPBB->getFirstNonPhi());
       RecipeBuilder.createHeaderMask();
-    else if (NeedsMasks)
-      RecipeBuilder.createBlockInMask(BB);
+    } else if (NeedsMasks) {
+      Builder.setInsertPoint(VPBB, VPBB->begin());
+      RecipeBuilder.createBlockInMask(HCFGBuilder.getIRBBForVPB(VPBB));
----------------
ayalz wrote:

Time to move edge masks and block masks to be cached according to VPBB's rather than IRBB's?
Rather than hacking VPlanHCFGBuilder and PlainCFGBuilder to record and retrieve IRBB for VPBB.

https://github.com/llvm/llvm-project/pull/124432