[llvm] [VPlan] Convert to concrete recipes before dissolving loop regions. NFCI (PR #141999)

[Luke Lau via llvm-commits]

https://github.com/lukel97 created https://github.com/llvm/llvm-project/pull/141999

After updating #118638 on tip of tree, expanding VPWidenIntOrFpInductionRecipes fails because it needs the loop region to get the latch to insert the increment into:

    VPBasicBlock *ExitingBB = Plan->getVectorLoopRegion()->getExitingBasicBlock();
    Builder.setInsertPoint(ExitingBB, ExitingBB->getTerminator()->getIterator());
    auto *Next = Builder.createNaryOp(AddOp, {Prev, Inc}, Flags,
                                      WidenIVR->getDebugLoc(), "vec.ind.next");

However after #117506, the region is dissolved so it doesn't work.

This shuffles the dissolveLoopRegions steps to be after convertToConcreteRecipes so we can use the region when expanding VPWidenIntOrFpInductionRecipes


>From 70c4fc11ab6e36f532f8065649a68c67aa165a79 Mon Sep 17 00:00:00 2001
From: Luke Lau <luke at igalia.com>
Date: Thu, 29 May 2025 18:55:20 +0100
Subject: [PATCH] [VPlan] Convert to concrete recipes before dissolving loop
 regions. NFCI

After updating #118638 on tip of tree, expanding VPWidenIntOrFpInductionRecipes fails because it needs the loop region to get the latch to insert the increment into:

    VPBasicBlock *ExitingBB = Plan->getVectorLoopRegion()->getExitingBasicBlock();
    Builder.setInsertPoint(ExitingBB, ExitingBB->getTerminator()->getIterator());
    auto *Next = Builder.createNaryOp(AddOp, {Prev, Inc}, Flags,
                                      WidenIVR->getDebugLoc(), "vec.ind.next");

However after #117506, the region is dissolved so it doesn't work.

This shuffles the dissolveLoopRegions steps to be after convertToConcreteRecipes so we can use the region when expanding VPWidenIntOrFpInductionRecipes
---
 llvm/lib/Transforms/Vectorize/LoopVectorize.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 90e224ea8f37a..6bd06410614de 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -7568,14 +7568,14 @@ DenseMap<const SCEV *, Value *> LoopVectorizationPlanner::executePlan(
       TTI.getRegisterBitWidth(TargetTransformInfo::RGK_FixedWidthVector));
   VPlanTransforms::removeDeadRecipes(BestVPlan);
 
+  VPlanTransforms::convertToConcreteRecipes(BestVPlan,
+                                            *Legal->getWidestInductionType());
   // Retrieve and store the middle block before dissolving regions. Regions are
   // dissolved after optimizing for VF and UF, which completely removes unneeded
   // loop regions first.
   VPBasicBlock *MiddleVPBB =
       BestVPlan.getVectorLoopRegion() ? BestVPlan.getMiddleBlock() : nullptr;
   VPlanTransforms::dissolveLoopRegions(BestVPlan);
-  VPlanTransforms::convertToConcreteRecipes(BestVPlan,
-                                            *Legal->getWidestInductionType());
   // Perform the actual loop transformation.
   VPTransformState State(&TTI, BestVF, LI, DT, ILV.AC, ILV.Builder, &BestVPlan,
                          OrigLoop->getParentLoop(),