[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));
+    }
 
-    // Introduce each ingredient into VPlan.
+    // Convert input VPInstructions to widened recipes.
     // TODO: Model and preserve debug intrinsics in VPlan.
-    for (Instruction &I : drop_end(BB->instructionsWithoutDebug(false))) {
-      Instruction *Instr = &I;
+    for (VPRecipeBase &R : make_early_inc_range(*VPBB)) {
+      auto *SingleDef = dyn_cast<VPSingleDefRecipe>(&R);
+      if (!isa<VPWidenPHIRecipe>(&R) &&
+          (!isa<VPInstruction>(SingleDef) || !SingleDef->getUnderlyingValue()))
+        continue;
+
+      if (match(&R, m_BranchOnCond(m_VPValue())) ||
+          (isa<VPInstruction>(&R) &&
+           cast<VPInstruction>(&R)->getOpcode() == Instruction::Switch)) {
+        R.eraseFromParent();
+        break;
+      }
+
+      // TODO: Gradually replace uses of underlying instruction by analyses on
+      // VPlan.
+      Instruction *Instr = SingleDef->getUnderlyingInstr();
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ayalz wrote:

nit: define Instr earlier to be reused above.

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