diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index deb8ee2d88055..cad11b4ff96a4 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -886,7 +886,6 @@ static std::optional<unsigned> getExtractIndex(const Instruction *E) {
   return *EI->idx_begin();
 }
 
-namespace llvm {
 /// Checks if the provided value does not require scheduling. It does not
 /// require scheduling if this is not an instruction or it is an instruction
 /// that does not read/write memory and all operands are either not instructions
@@ -901,18 +900,18 @@ static bool isUsedOutsideBlock(Value *V);
 /// require scheduling if all operands and all users do not need to be scheduled
 /// in the current basic block.
 static bool doesNotNeedToBeScheduled(Value *V);
-} // namespace llvm
 
-namespace {
 /// \returns true if \p Opcode is allowed as part of the main/alternate
 /// instruction for SLP vectorization.
 ///
 /// Example of unsupported opcode is SDIV that can potentially cause UB if the
 /// "shuffled out" lane would result in division by zero.
-bool isValidForAlternation(unsigned Opcode) {
+static bool isValidForAlternation(unsigned Opcode) {
   return !Instruction::isIntDivRem(Opcode);
 }
 
+namespace {
+
 /// Helper class that determines VL can use the same opcode.
 /// Alternate instruction is supported. In addition, it supports interchangeable
 /// instruction. An interchangeable instruction is an instruction that can be
@@ -1816,8 +1815,6 @@ static SmallVector<Constant *> replicateMask(ArrayRef<Constant *> Val,
   return NewVal;
 }
 
-namespace llvm {
-
 static void inversePermutation(ArrayRef<unsigned> Indices,
                                SmallVectorImpl<int> &Mask) {
   Mask.clear();
@@ -1922,10 +1919,8 @@ getNumberOfParts(const TargetTransformInfo &TTI, VectorType *VecTy,
   return NumParts;
 }
 
-namespace slpvectorizer {
-
 /// Bottom Up SLP Vectorizer.
-class BoUpSLP {
+class slpvectorizer::BoUpSLP {
   class TreeEntry;
   class ScheduleEntity;
   class ScheduleData;
@@ -6084,9 +6079,7 @@ class BoUpSLP {
   DenseSet<unsigned> ExtraBitWidthNodes;
 };
 
-} // end namespace slpvectorizer
-
-template <> struct DenseMapInfo<BoUpSLP::EdgeInfo> {
+template <> struct llvm::DenseMapInfo<BoUpSLP::EdgeInfo> {
   using FirstInfo = DenseMapInfo<BoUpSLP::TreeEntry *>;
   using SecondInfo = DenseMapInfo<unsigned>;
   static BoUpSLP::EdgeInfo getEmptyKey() {
@@ -6110,7 +6103,7 @@ template <> struct DenseMapInfo<BoUpSLP::EdgeInfo> {
   }
 };
 
-template <> struct GraphTraits<BoUpSLP *> {
+template <> struct llvm::GraphTraits<BoUpSLP *> {
   using TreeEntry = BoUpSLP::TreeEntry;
 
   /// NodeRef has to be a pointer per the GraphWriter.
@@ -6171,7 +6164,8 @@ template <> struct GraphTraits<BoUpSLP *> {
   static unsigned size(BoUpSLP *R) { return R->VectorizableTree.size(); }
 };
 
-template <> struct DOTGraphTraits<BoUpSLP *> : public DefaultDOTGraphTraits {
+template <>
+struct llvm::DOTGraphTraits<BoUpSLP *> : public DefaultDOTGraphTraits {
   using TreeEntry = BoUpSLP::TreeEntry;
 
   DOTGraphTraits(bool IsSimple = false) : DefaultDOTGraphTraits(IsSimple) {}
@@ -6205,8 +6199,6 @@ template <> struct DOTGraphTraits<BoUpSLP *> : public DefaultDOTGraphTraits {
   }
 };
 
-} // end namespace llvm
-
 BoUpSLP::~BoUpSLP() {
   SmallVector<WeakTrackingVH> DeadInsts;
   for (auto *I : DeletedInstructions) {
diff --git a/llvm/lib/Transforms/Vectorize/VPlanPatternMatch.h b/llvm/lib/Transforms/Vectorize/VPlanPatternMatch.h
index 447e2d70d941f..5d65d9bf34bcc 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanPatternMatch.h
+++ b/llvm/lib/Transforms/Vectorize/VPlanPatternMatch.h
@@ -17,8 +17,7 @@
 
 #include "VPlan.h"
 
-namespace llvm {
-namespace VPlanPatternMatch {
+namespace llvm::VPlanPatternMatch {
 
 template <typename Val, typename Pattern> bool match(Val *V, const Pattern &P) {
   return P.match(V);
@@ -878,7 +877,6 @@ template <typename T> inline OneUse_match<T> m_OneUse(const T &SubPattern) {
   return SubPattern;
 }
 
-} // namespace VPlanPatternMatch
-} // namespace llvm
+} // namespace llvm::VPlanPatternMatch
 
 #endif