diff --git a/llvm/include/llvm/Analysis/InlineCost.h b/llvm/include/llvm/Analysis/InlineCost.h
index 7e567895215a1..57f452853d2d6 100644
--- a/llvm/include/llvm/Analysis/InlineCost.h
+++ b/llvm/include/llvm/Analysis/InlineCost.h
@@ -102,7 +102,7 @@ class InlineCost {
   const char *Reason = nullptr;
 
   /// The cost-benefit pair computed by cost-benefit analysis.
-  std::optional<CostBenefitPair> CostBenefit = std::nullopt;
+  std::optional<CostBenefitPair> CostBenefit;
 
   // Trivial constructor, interesting logic in the factory functions below.
   InlineCost(int Cost, int Threshold, int StaticBonusApplied,
diff --git a/llvm/include/llvm/DWP/DWP.h b/llvm/include/llvm/DWP/DWP.h
index ff2614000fe10..543354d86bbb5 100644
--- a/llvm/include/llvm/DWP/DWP.h
+++ b/llvm/include/llvm/DWP/DWP.h
@@ -44,7 +44,7 @@ struct InfoSectionUnitHeader {
 
   // dwo_id field. This resides in the header only if Version >= 5.
   // In earlier versions, it is read from DW_AT_GNU_dwo_id.
-  std::optional<uint64_t> Signature = std::nullopt;
+  std::optional<uint64_t> Signature;
 
   // Derived from the length of Length field.
   dwarf::DwarfFormat Format = dwarf::DwarfFormat::DWARF32;
diff --git a/llvm/include/llvm/IR/Instructions.h b/llvm/include/llvm/IR/Instructions.h
index 1ba544dd5143a..3177cfe0a6a01 100644
--- a/llvm/include/llvm/IR/Instructions.h
+++ b/llvm/include/llvm/IR/Instructions.h
@@ -3612,7 +3612,7 @@ class SwitchInst : public Instruction {
 /// their prof branch_weights metadata.
 class SwitchInstProfUpdateWrapper {
   SwitchInst &SI;
-  std::optional<SmallVector<uint32_t, 8>> Weights = std::nullopt;
+  std::optional<SmallVector<uint32_t, 8>> Weights;
   bool Changed = false;
 
 protected:
diff --git a/llvm/include/llvm/LTO/Config.h b/llvm/include/llvm/LTO/Config.h
index 2dbe284ff449b..4c793697da022 100644
--- a/llvm/include/llvm/LTO/Config.h
+++ b/llvm/include/llvm/LTO/Config.h
@@ -53,7 +53,7 @@ struct Config {
   /// For adding passes that run right before codegen.
   std::function<void(legacy::PassManager &)> PreCodeGenPassesHook;
   std::optional<Reloc::Model> RelocModel = Reloc::PIC_;
-  std::optional<CodeModel::Model> CodeModel = std::nullopt;
+  std::optional<CodeModel::Model> CodeModel;
   CodeGenOpt::Level CGOptLevel = CodeGenOpt::Default;
   CodeGenFileType CGFileType = CGFT_ObjectFile;
   unsigned OptLevel = 2;
diff --git a/llvm/include/llvm/Object/ELF.h b/llvm/include/llvm/Object/ELF.h
index ed2afc6042245..9f90ab2e702aa 100644
--- a/llvm/include/llvm/Object/ELF.h
+++ b/llvm/include/llvm/Object/ELF.h
@@ -120,7 +120,7 @@ template <class T> struct DataRegion {
   }
 
   const T *First;
-  std::optional<uint64_t> Size = std::nullopt;
+  std::optional<uint64_t> Size;
   const uint8_t *BufEnd = nullptr;
 };
 
diff --git a/llvm/include/llvm/Target/TargetMachine.h b/llvm/include/llvm/Target/TargetMachine.h
index 2dd1c81995130..57365d2c74d69 100644
--- a/llvm/include/llvm/Target/TargetMachine.h
+++ b/llvm/include/llvm/Target/TargetMachine.h
@@ -110,7 +110,7 @@ class TargetMachine {
   unsigned O0WantsFastISel : 1;
 
   // PGO related tunables.
-  std::optional<PGOOptions> PGOOption = std::nullopt;
+  std::optional<PGOOptions> PGOOption;
 
 public:
   const TargetOptions DefaultOptions;
diff --git a/llvm/include/llvm/Transforms/IPO/Attributor.h b/llvm/include/llvm/Transforms/IPO/Attributor.h
index 59a0d2ae6f882..1d813cb8b3385 100644
--- a/llvm/include/llvm/Transforms/IPO/Attributor.h
+++ b/llvm/include/llvm/Transforms/IPO/Attributor.h
@@ -1385,7 +1385,7 @@ struct AttributorConfig {
   DenseSet<const char *> *Allowed = nullptr;
 
   /// Maximum number of iterations to run until fixpoint.
-  std::optional<unsigned> MaxFixpointIterations = std::nullopt;
+  std::optional<unsigned> MaxFixpointIterations;
 
   /// A callback function that returns an ORE object from a Function pointer.
   ///{
diff --git a/llvm/include/llvm/Transforms/Scalar/GVN.h b/llvm/include/llvm/Transforms/Scalar/GVN.h
index 888a537ba2596..b043cfb2c258c 100644
--- a/llvm/include/llvm/Transforms/Scalar/GVN.h
+++ b/llvm/include/llvm/Transforms/Scalar/GVN.h
@@ -72,11 +72,11 @@ class GVNLegacyPass;
 /// Intended use is to create a default object, modify parameters with
 /// additional setters and then pass it to GVN.
 struct GVNOptions {
-  std::optional<bool> AllowPRE = std::nullopt;
-  std::optional<bool> AllowLoadPRE = std::nullopt;
-  std::optional<bool> AllowLoadInLoopPRE = std::nullopt;
-  std::optional<bool> AllowLoadPRESplitBackedge = std::nullopt;
-  std::optional<bool> AllowMemDep = std::nullopt;
+  std::optional<bool> AllowPRE;
+  std::optional<bool> AllowLoadPRE;
+  std::optional<bool> AllowLoadInLoopPRE;
+  std::optional<bool> AllowLoadPRESplitBackedge;
+  std::optional<bool> AllowMemDep;
 
   GVNOptions() = default;
 
diff --git a/llvm/lib/Analysis/InlineCost.cpp b/llvm/lib/Analysis/InlineCost.cpp
index e39940ed6a9b5..309da995e5f3b 100644
--- a/llvm/lib/Analysis/InlineCost.cpp
+++ b/llvm/lib/Analysis/InlineCost.cpp
@@ -584,7 +584,7 @@ class InlineCostCallAnalyzer final : public CallAnalyzer {
   bool DecidedByCostBenefit = false;
 
   // The cost-benefit pair computed by cost-benefit analysis.
-  std::optional<CostBenefitPair> CostBenefit = std::nullopt;
+  std::optional<CostBenefitPair> CostBenefit;
 
   bool SingleBB = true;
 
diff --git a/llvm/lib/Analysis/MemorySSA.cpp b/llvm/lib/Analysis/MemorySSA.cpp
index 0e6a12261e23a..fec7a0fd35795 100644
--- a/llvm/lib/Analysis/MemorySSA.cpp
+++ b/llvm/lib/Analysis/MemorySSA.cpp
@@ -719,7 +719,7 @@ class ClobberWalker {
     T &curNode() const { return W->Paths[*N]; }
 
     Walker *W = nullptr;
-    std::optional<ListIndex> N = std::nullopt;
+    std::optional<ListIndex> N;
   };
 
   using def_path_iterator = generic_def_path_iterator<DefPath, ClobberWalker>;
diff --git a/llvm/lib/IR/DebugInfo.cpp b/llvm/lib/IR/DebugInfo.cpp
index 2a6f9b9673a36..94e1ad211eeab 100644
--- a/llvm/lib/IR/DebugInfo.cpp
+++ b/llvm/lib/IR/DebugInfo.cpp
@@ -1830,7 +1830,7 @@ void at::trackAssignments(Function::iterator Start, Function::iterator End,
   for (auto BBI = Start; BBI != End; ++BBI) {
     for (Instruction &I : *BBI) {
 
-      std::optional<AssignmentInfo> Info = std::nullopt;
+      std::optional<AssignmentInfo> Info;
       Value *ValueComponent = nullptr;
       Value *DestComponent = nullptr;
       if (auto *AI = dyn_cast<AllocaInst>(&I)) {
diff --git a/llvm/lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp b/llvm/lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp
index 1859195de86ef..afea2b2f5f754 100644
--- a/llvm/lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp
+++ b/llvm/lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp
@@ -99,7 +99,7 @@ using LdStPairFlags = struct LdStPairFlags {
   // If not none, RenameReg can be used to rename the result register of the
   // first store in a pair. Currently this only works when merging stores
   // forward.
-  std::optional<MCPhysReg> RenameReg = std::nullopt;
+  std::optional<MCPhysReg> RenameReg;
 
   LdStPairFlags() = default;
 
diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 48dcce72ee45c..5baa7e78a58f6 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -1697,7 +1697,7 @@ class BoUpSLP {
       // Sometimes we have more than one option (e.g., Opcode and Undefs), so we
       // are using the score to differentiate between the two.
       struct BestOpData {
-        std::optional<unsigned> Idx = std::nullopt;
+        std::optional<unsigned> Idx;
         unsigned Score = 0;
       } BestOp;
       BestOp.Score =
diff --git a/llvm/unittests/IR/DebugInfoTest.cpp b/llvm/unittests/IR/DebugInfoTest.cpp
index 1930ecdd8cc9f..8a5157f292bbb 100644
--- a/llvm/unittests/IR/DebugInfoTest.cpp
+++ b/llvm/unittests/IR/DebugInfoTest.cpp
@@ -198,8 +198,8 @@ TEST(DIBuiler, CreateFile) {
   DIFile *F = DIB.createFile("main.c", "/");
   EXPECT_EQ(std::nullopt, F->getSource());
 
-  std::optional<DIFile::ChecksumInfo<StringRef>> Checksum = std::nullopt;
-  std::optional<StringRef> Source = std::nullopt;
+  std::optional<DIFile::ChecksumInfo<StringRef>> Checksum;
+  std::optional<StringRef> Source;
   F = DIB.createFile("main.c", "/", Checksum, Source);
   EXPECT_EQ(Source, F->getSource());
 
diff --git a/llvm/unittests/IR/MetadataTest.cpp b/llvm/unittests/IR/MetadataTest.cpp
index 05f1cc17dfdf3..926490f6b0b05 100644
--- a/llvm/unittests/IR/MetadataTest.cpp
+++ b/llvm/unittests/IR/MetadataTest.cpp
@@ -2219,8 +2219,8 @@ TEST_F(DIFileTest, EmptySource) {
   DIFile *N = DIFile::get(Context, "file", "dir");
   EXPECT_EQ(std::nullopt, N->getSource());
 
-  std::optional<DIFile::ChecksumInfo<StringRef>> Checksum = std::nullopt;
-  std::optional<StringRef> Source = std::nullopt;
+  std::optional<DIFile::ChecksumInfo<StringRef>> Checksum;
+  std::optional<StringRef> Source;
   N = DIFile::get(Context, "file", "dir", Checksum, Source);
   EXPECT_EQ(Source, N->getSource());