[llvm] [IVDesc] Make getCastInsts return an ArrayRef (NFC) (PR #169021)

[Ramkumar Ramachandra via llvm-commits]

https://github.com/artagnon updated https://github.com/llvm/llvm-project/pull/169021

>From e00cdcda53b61b1bc9583ad5e6282dac2f7154c6 Mon Sep 17 00:00:00 2001
From: Ramkumar Ramachandra <ramkumar.ramachandra at codasip.com>
Date: Fri, 21 Nov 2025 10:27:16 +0000
Subject: [PATCH 1/2] [IVDesc] Make getCastInsts return an ArrayRef (NFC)

To make it clear that the return value is immutable.
---
 llvm/include/llvm/Analysis/IVDescriptors.h                  | 4 +---
 llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp | 2 +-
 llvm/lib/Transforms/Vectorize/LoopVectorize.cpp             | 3 +--
 llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp           | 2 +-
 4 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/llvm/include/llvm/Analysis/IVDescriptors.h b/llvm/include/llvm/Analysis/IVDescriptors.h
index 654a5f10cea96..724ab8364249d 100644
--- a/llvm/include/llvm/Analysis/IVDescriptors.h
+++ b/llvm/include/llvm/Analysis/IVDescriptors.h
@@ -454,9 +454,7 @@ class InductionDescriptor {
   /// Returns a reference to the type cast instructions in the induction
   /// update chain, that are redundant when guarded with a runtime
   /// SCEV overflow check.
-  const SmallVectorImpl<Instruction *> &getCastInsts() const {
-    return RedundantCasts;
-  }
+  ArrayRef<Instruction *> getCastInsts() const { return RedundantCasts; }
 
 private:
   /// Private constructor - used by \c isInductionPHI.
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
index 86e742ca5fec1..ba21bbbe112e6 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
@@ -684,7 +684,7 @@ void LoopVectorizationLegality::addInductionPhi(
   // in the vectorized loop body, record them here. All casts could be recorded
   // here for ignoring, but suffices to record only the first (as it is the
   // only one that may bw used outside the cast sequence).
-  const SmallVectorImpl<Instruction *> &Casts = ID.getCastInsts();
+  ArrayRef<Instruction *> Casts = ID.getCastInsts();
   if (!Casts.empty())
     InductionCastsToIgnore.insert(*Casts.begin());
 
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 5b8725178521e..5ae90aa76c27d 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -6575,8 +6575,7 @@ void LoopVectorizationCostModel::collectValuesToIgnore() {
   // detection.
   for (const auto &Induction : Legal->getInductionVars()) {
     const InductionDescriptor &IndDes = Induction.second;
-    const SmallVectorImpl<Instruction *> &Casts = IndDes.getCastInsts();
-    VecValuesToIgnore.insert_range(Casts);
+    VecValuesToIgnore.insert_range(IndDes.getCastInsts());
   }
 }
 
diff --git a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
index a6a03c0d805fd..6cffdcce4013d 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
@@ -512,7 +512,7 @@ static void removeRedundantInductionCasts(VPlan &Plan) {
     // replace it with the original IV. Note that only the final cast is
     // expected to have users outside the cast-chain and the dead casts left
     // over will be cleaned up later.
-    auto &Casts = IV->getInductionDescriptor().getCastInsts();
+    ArrayRef<Instruction *> Casts = IV->getInductionDescriptor().getCastInsts();
     VPValue *FindMyCast = IV;
     for (Instruction *IRCast : reverse(Casts)) {
       VPSingleDefRecipe *FoundUserCast = nullptr;

>From 656efc1f26126abf71fd7764bafcd5690a53c36c Mon Sep 17 00:00:00 2001
From: Ramkumar Ramachandra <ramkumar.ramachandra at codasip.com>
Date: Mon, 24 Nov 2025 08:26:44 +0000
Subject: [PATCH 2/2] [IVDesc] Update hdr comment

---
 llvm/include/llvm/Analysis/IVDescriptors.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/include/llvm/Analysis/IVDescriptors.h b/llvm/include/llvm/Analysis/IVDescriptors.h
index 724ab8364249d..2c8484fde5b16 100644
--- a/llvm/include/llvm/Analysis/IVDescriptors.h
+++ b/llvm/include/llvm/Analysis/IVDescriptors.h
@@ -451,7 +451,7 @@ class InductionDescriptor {
                           : Instruction::BinaryOpsEnd;
   }
 
-  /// Returns a reference to the type cast instructions in the induction
+  /// Returns an ArrayRef to the type cast instructions in the induction
   /// update chain, that are redundant when guarded with a runtime
   /// SCEV overflow check.
   ArrayRef<Instruction *> getCastInsts() const { return RedundantCasts; }