diff --git a/mlir/lib/Analysis/AffineStructures.cpp b/mlir/lib/Analysis/AffineStructures.cpp
--- a/mlir/lib/Analysis/AffineStructures.cpp
+++ b/mlir/lib/Analysis/AffineStructures.cpp
@@ -3346,7 +3346,7 @@
     newSyms->append(syms.begin(), syms.end());
   }
 
-  for (auto operand : llvm::enumerate(operands)) {
+  for (const auto &operand : llvm::enumerate(operands)) {
     // Compute replacement dim/sym of operand.
     AffineExpr replacement;
     auto dimIt = std::find(dims.begin(), dims.end(), operand.value());
diff --git a/mlir/lib/Analysis/LoopAnalysis.cpp b/mlir/lib/Analysis/LoopAnalysis.cpp
--- a/mlir/lib/Analysis/LoopAnalysis.cpp
+++ b/mlir/lib/Analysis/LoopAnalysis.cpp
@@ -353,7 +353,8 @@
   // Work backwards over the body of the block so that the shift of a use's
   // ancestor operation in the block gets recorded before it's looked up.
   DenseMap<Operation *, uint64_t> forBodyShift;
-  for (auto it : llvm::enumerate(llvm::reverse(forBody->getOperations()))) {
+  for (const auto &it :
+       llvm::enumerate(llvm::reverse(forBody->getOperations()))) {
     auto &op = it.value();
 
     // Get the index of the current operation, note that we are iterating in
diff --git a/mlir/lib/Analysis/NumberOfExecutions.cpp b/mlir/lib/Analysis/NumberOfExecutions.cpp
--- a/mlir/lib/Analysis/NumberOfExecutions.cpp
+++ b/mlir/lib/Analysis/NumberOfExecutions.cpp
@@ -52,7 +52,7 @@
   // Query RegionBranchOpInterface interface if it is available.
   if (auto regionInterface = dyn_cast<RegionBranchOpInterface>(parentOp)) {
     SmallVector<Attribute, 4> operands(parentOp->getNumOperands());
-    for (auto operandIt : llvm::enumerate(parentOp->getOperands()))
+    for (const auto &operandIt : llvm::enumerate(parentOp->getOperands()))
       matchPattern(operandIt.value(), m_Constant(&operands[operandIt.index()]));
 
     regionInterface.getNumRegionInvocations(operands, numRegionsInvocations);
diff --git a/mlir/lib/Analysis/SliceAnalysis.cpp b/mlir/lib/Analysis/SliceAnalysis.cpp
--- a/mlir/lib/Analysis/SliceAnalysis.cpp
+++ b/mlir/lib/Analysis/SliceAnalysis.cpp
@@ -86,7 +86,7 @@
   if (filter && !filter(op))
     return;
 
-  for (auto en : llvm::enumerate(op->getOperands())) {
+  for (const auto &en : llvm::enumerate(op->getOperands())) {
     auto operand = en.value();
     if (auto *definingOp = operand.getDefiningOp()) {
       if (backwardSlice->count(definingOp) == 0)
diff --git a/mlir/lib/Bindings/Python/IRCore.cpp b/mlir/lib/Bindings/Python/IRCore.cpp
--- a/mlir/lib/Bindings/Python/IRCore.cpp
+++ b/mlir/lib/Bindings/Python/IRCore.cpp
@@ -1154,7 +1154,7 @@
   resultTypes.reserve(resultTypeList.size());
   if (resultSegmentSpecObj.is_none()) {
     // Non-variadic result unpacking.
-    for (auto it : llvm::enumerate(resultTypeList)) {
+    for (const auto &it : llvm::enumerate(resultTypeList)) {
       try {
         resultTypes.push_back(py::cast<PyType *>(it.value()));
         if (!resultTypes.back())
@@ -1178,7 +1178,7 @@
                                 .str());
     }
     resultSegmentLengths.reserve(resultTypeList.size());
-    for (auto it :
+    for (const auto &it :
          llvm::enumerate(llvm::zip(resultTypeList, resultSegmentSpec))) {
       int segmentSpec = std::get<1>(it.value());
       if (segmentSpec == 1 || segmentSpec == 0) {
@@ -1239,7 +1239,7 @@
   operands.reserve(operands.size());
   if (operandSegmentSpecObj.is_none()) {
     // Non-sized operand unpacking.
-    for (auto it : llvm::enumerate(operandList)) {
+    for (const auto &it : llvm::enumerate(operandList)) {
       try {
         operands.push_back(py::cast<PyValue *>(it.value()));
         if (!operands.back())
@@ -1263,7 +1263,7 @@
                                 .str());
     }
     operandSegmentLengths.reserve(operandList.size());
-    for (auto it :
+    for (const auto &it :
          llvm::enumerate(llvm::zip(operandList, operandSegmentSpec))) {
       int segmentSpec = std::get<1>(it.value());
       if (segmentSpec == 1 || segmentSpec == 0) {
diff --git a/mlir/lib/Conversion/GPUCommon/GPUOpsLowering.cpp b/mlir/lib/Conversion/GPUCommon/GPUOpsLowering.cpp
--- a/mlir/lib/Conversion/GPUCommon/GPUOpsLowering.cpp
+++ b/mlir/lib/Conversion/GPUCommon/GPUOpsLowering.cpp
@@ -22,7 +22,7 @@
 
   SmallVector<LLVM::GlobalOp, 3> workgroupBuffers;
   workgroupBuffers.reserve(gpuFuncOp.getNumWorkgroupAttributions());
-  for (auto en : llvm::enumerate(gpuFuncOp.getWorkgroupAttributions())) {
+  for (const auto &en : llvm::enumerate(gpuFuncOp.getWorkgroupAttributions())) {
     Value attribution = en.value();
 
     auto type = attribution.getType().dyn_cast<MemRefType>();
@@ -89,7 +89,7 @@
     if (!workgroupBuffers.empty())
       zero = rewriter.create<LLVM::ConstantOp>(loc, i32Type,
                                                rewriter.getI32IntegerAttr(0));
-    for (auto en : llvm::enumerate(workgroupBuffers)) {
+    for (const auto &en : llvm::enumerate(workgroupBuffers)) {
       LLVM::GlobalOp global = en.value();
       Value address = rewriter.create<LLVM::AddressOfOp>(loc, global);
       auto elementType =
@@ -112,7 +112,7 @@
     // Rewrite private memory attributions to alloca'ed buffers.
     unsigned numWorkgroupAttributions = gpuFuncOp.getNumWorkgroupAttributions();
     auto int64Ty = IntegerType::get(rewriter.getContext(), 64);
-    for (auto en : llvm::enumerate(gpuFuncOp.getPrivateAttributions())) {
+    for (const auto &en : llvm::enumerate(gpuFuncOp.getPrivateAttributions())) {
       Value attribution = en.value();
       auto type = attribution.getType().cast<MemRefType>();
       assert(type && type.hasStaticShape() && "unexpected type in attribution");
diff --git a/mlir/lib/Conversion/GPUCommon/GPUToLLVMConversion.cpp b/mlir/lib/Conversion/GPUCommon/GPUToLLVMConversion.cpp
--- a/mlir/lib/Conversion/GPUCommon/GPUToLLVMConversion.cpp
+++ b/mlir/lib/Conversion/GPUCommon/GPUToLLVMConversion.cpp
@@ -634,7 +634,7 @@
                                                  arraySize, /*alignment=*/0);
   auto zero = builder.create<LLVM::ConstantOp>(loc, llvmInt32Type,
                                                builder.getI32IntegerAttr(0));
-  for (auto en : llvm::enumerate(arguments)) {
+  for (const auto &en : llvm::enumerate(arguments)) {
     auto index = builder.create<LLVM::ConstantOp>(
         loc, llvmInt32Type, builder.getI32IntegerAttr(en.index()));
     auto fieldPtr = builder.create<LLVM::GEPOp>(
diff --git a/mlir/lib/Conversion/GPUToSPIRV/GPUToSPIRV.cpp b/mlir/lib/Conversion/GPUToSPIRV/GPUToSPIRV.cpp
--- a/mlir/lib/Conversion/GPUToSPIRV/GPUToSPIRV.cpp
+++ b/mlir/lib/Conversion/GPUToSPIRV/GPUToSPIRV.cpp
@@ -206,7 +206,7 @@
   // LowerABIAttributesPass.
   TypeConverter::SignatureConversion signatureConverter(fnType.getNumInputs());
   {
-    for (auto argType : enumerate(funcOp.getType().getInputs())) {
+    for (const auto &argType : enumerate(funcOp.getType().getInputs())) {
       auto convertedType = typeConverter.convertType(argType.value());
       signatureConverter.addInputs(argType.index(), convertedType);
     }
diff --git a/mlir/lib/Conversion/GPUToVulkan/ConvertLaunchFuncToVulkanCalls.cpp b/mlir/lib/Conversion/GPUToVulkan/ConvertLaunchFuncToVulkanCalls.cpp
--- a/mlir/lib/Conversion/GPUToVulkan/ConvertLaunchFuncToVulkanCalls.cpp
+++ b/mlir/lib/Conversion/GPUToVulkan/ConvertLaunchFuncToVulkanCalls.cpp
@@ -222,7 +222,7 @@
   Value descriptorSet = builder.create<LLVM::ConstantOp>(
       loc, getInt32Type(), builder.getI32IntegerAttr(0));
 
-  for (auto en :
+  for (const auto &en :
        llvm::enumerate(cInterfaceVulkanLaunchCallOp.getOperands().drop_front(
            kVulkanLaunchNumConfigOperands))) {
     // Create LLVM constant for the descriptor binding index.
diff --git a/mlir/lib/Conversion/LLVMCommon/Pattern.cpp b/mlir/lib/Conversion/LLVMCommon/Pattern.cpp
--- a/mlir/lib/Conversion/LLVMCommon/Pattern.cpp
+++ b/mlir/lib/Conversion/LLVMCommon/Pattern.cpp
@@ -213,11 +213,11 @@
                              createIndexConstant(rewriter, loc, 0));
 
   // Fields 4: Sizes.
-  for (auto en : llvm::enumerate(sizes))
+  for (const auto &en : llvm::enumerate(sizes))
     memRefDescriptor.setSize(rewriter, loc, en.index(), en.value());
 
   // Field 5: Strides.
-  for (auto en : llvm::enumerate(strides))
+  for (const auto &en : llvm::enumerate(strides))
     memRefDescriptor.setStride(rewriter, loc, en.index(), en.value());
 
   return memRefDescriptor;
diff --git a/mlir/lib/Conversion/LLVMCommon/VectorPattern.cpp b/mlir/lib/Conversion/LLVMCommon/VectorPattern.cpp
--- a/mlir/lib/Conversion/LLVMCommon/VectorPattern.cpp
+++ b/mlir/lib/Conversion/LLVMCommon/VectorPattern.cpp
@@ -101,7 +101,7 @@
     // For this unrolled `position` corresponding to the `linearIndex`^th
     // element, extract operand vectors
     SmallVector<Value, 4> extractedOperands;
-    for (auto operand : llvm::enumerate(operands)) {
+    for (const auto &operand : llvm::enumerate(operands)) {
       extractedOperands.push_back(rewriter.create<LLVM::ExtractValueOp>(
           loc, operand1DVectorTypes[operand.index()], operand.value(),
           position));
diff --git a/mlir/lib/Conversion/MemRefToLLVM/MemRefToLLVM.cpp b/mlir/lib/Conversion/MemRefToLLVM/MemRefToLLVM.cpp
--- a/mlir/lib/Conversion/MemRefToLLVM/MemRefToLLVM.cpp
+++ b/mlir/lib/Conversion/MemRefToLLVM/MemRefToLLVM.cpp
@@ -1417,7 +1417,8 @@
     targetMemRef.setOffset(rewriter, loc, viewMemRef.offset(rewriter, loc));
 
     // Iterate over the dimensions and apply size/stride permutation.
-    for (auto en : llvm::enumerate(transposeOp.permutation().getResults())) {
+    for (const auto &en :
+         llvm::enumerate(transposeOp.permutation().getResults())) {
       int sourcePos = en.index();
       int targetPos = en.value().cast<AffineDimExpr>().getPosition();
       targetMemRef.setSize(rewriter, loc, targetPos,
diff --git a/mlir/lib/Conversion/PDLToPDLInterp/PDLToPDLInterp.cpp b/mlir/lib/Conversion/PDLToPDLInterp/PDLToPDLInterp.cpp
--- a/mlir/lib/Conversion/PDLToPDLInterp/PDLToPDLInterp.cpp
+++ b/mlir/lib/Conversion/PDLToPDLInterp/PDLToPDLInterp.cpp
@@ -736,7 +736,7 @@
   bool seenVariableLength = false;
   Type valueTy = builder.getType<pdl::ValueType>();
   Type valueRangeTy = pdl::RangeType::get(valueTy);
-  for (auto it : llvm::enumerate(resultTys)) {
+  for (const auto &it : llvm::enumerate(resultTys)) {
     Value &type = rewriteValues[it.value()];
     if (type)
       continue;
@@ -862,7 +862,7 @@
   // Otherwise, handle inference for each of the result types individually.
   OperandRange resultTypeValues = op.types();
   types.reserve(resultTypeValues.size());
-  for (auto it : llvm::enumerate(resultTypeValues)) {
+  for (const auto &it : llvm::enumerate(resultTypeValues)) {
     Value resultType = it.value();
 
     // Check for an already translated value.
diff --git a/mlir/lib/Conversion/PDLToPDLInterp/PredicateTree.cpp b/mlir/lib/Conversion/PDLToPDLInterp/PredicateTree.cpp
--- a/mlir/lib/Conversion/PDLToPDLInterp/PredicateTree.cpp
+++ b/mlir/lib/Conversion/PDLToPDLInterp/PredicateTree.cpp
@@ -162,7 +162,7 @@
                       builder.getAllOperands(opPos));
   } else {
     bool foundVariableLength = false;
-    for (auto operandIt : llvm::enumerate(operands)) {
+    for (const auto &operandIt : llvm::enumerate(operands)) {
       bool isVariadic = operandIt.value().getType().isa<pdl::RangeType>();
       foundVariableLength |= isVariadic;
 
@@ -460,7 +460,7 @@
             }
 
             // Default case: visit all the operands.
-            for (auto p : llvm::enumerate(operationOp.operands()))
+            for (const auto &p : llvm::enumerate(operationOp.operands()))
               toVisit.emplace(p.value(), entry.value, p.index(),
                               entry.depth + 1);
           })
diff --git a/mlir/lib/Conversion/SCFToGPU/SCFToGPU.cpp b/mlir/lib/Conversion/SCFToGPU/SCFToGPU.cpp
--- a/mlir/lib/Conversion/SCFToGPU/SCFToGPU.cpp
+++ b/mlir/lib/Conversion/SCFToGPU/SCFToGPU.cpp
@@ -261,7 +261,7 @@
   builder.setInsertionPointToStart(&launchOp.body().front());
   auto *lbArgumentIt = lbs.begin();
   auto *stepArgumentIt = steps.begin();
-  for (auto en : llvm::enumerate(ivs)) {
+  for (const auto &en : llvm::enumerate(ivs)) {
     Value id =
         en.index() < numBlockDims
             ? getDim3Value(launchOp.getBlockIds(), en.index())
diff --git a/mlir/lib/Conversion/SCFToSPIRV/SCFToSPIRV.cpp b/mlir/lib/Conversion/SCFToSPIRV/SCFToSPIRV.cpp
--- a/mlir/lib/Conversion/SCFToSPIRV/SCFToSPIRV.cpp
+++ b/mlir/lib/Conversion/SCFToSPIRV/SCFToSPIRV.cpp
@@ -387,7 +387,7 @@
   // the before region, which may not matching the whole op's result. Instead,
   // the scf.condition op returns values matching the whole op's results. So we
   // need to create/load/store variables according to that.
-  for (auto it : llvm::enumerate(condArgs)) {
+  for (const auto &it : llvm::enumerate(condArgs)) {
     auto res = it.value();
     auto i = it.index();
     auto pointerType =
diff --git a/mlir/lib/Conversion/SPIRVToLLVM/ConvertLaunchFuncToLLVMCalls.cpp b/mlir/lib/Conversion/SPIRVToLLVM/ConvertLaunchFuncToLLVMCalls.cpp
--- a/mlir/lib/Conversion/SPIRVToLLVM/ConvertLaunchFuncToLLVMCalls.cpp
+++ b/mlir/lib/Conversion/SPIRVToLLVM/ConvertLaunchFuncToLLVMCalls.cpp
@@ -208,7 +208,7 @@
     SmallVector<CopyInfo, 4> copyInfo;
     auto numKernelOperands = launchOp.getNumKernelOperands();
     auto kernelOperands = adaptor.getOperands().take_back(numKernelOperands);
-    for (auto operand : llvm::enumerate(kernelOperands)) {
+    for (const auto &operand : llvm::enumerate(kernelOperands)) {
       // Check if the kernel's operand is a ranked memref.
       auto memRefType = launchOp.getKernelOperand(operand.index())
                             .getType()
diff --git a/mlir/lib/Conversion/StandardToLLVM/StandardToLLVM.cpp b/mlir/lib/Conversion/StandardToLLVM/StandardToLLVM.cpp
--- a/mlir/lib/Conversion/StandardToLLVM/StandardToLLVM.cpp
+++ b/mlir/lib/Conversion/StandardToLLVM/StandardToLLVM.cpp
@@ -254,7 +254,7 @@
           rewriter.getNamedAttr(function_like_impl::getArgDictAttrName(),
                                 rewriter.getArrayAttr(newArgAttrs)));
     }
-    for (auto pair : llvm::enumerate(attributes)) {
+    for (const auto &pair : llvm::enumerate(attributes)) {
       if (pair.value().getName() == "llvm.linkage") {
         attributes.erase(attributes.begin() + pair.index());
         break;
diff --git a/mlir/lib/Conversion/TosaToLinalg/TosaToLinalg.cpp b/mlir/lib/Conversion/TosaToLinalg/TosaToLinalg.cpp
--- a/mlir/lib/Conversion/TosaToLinalg/TosaToLinalg.cpp
+++ b/mlir/lib/Conversion/TosaToLinalg/TosaToLinalg.cpp
@@ -725,7 +725,7 @@
     SmallVector<int64_t, 5> newShape;
     SmallVector<AffineExpr, 4> affineExprs;
     newShape.reserve(type.getRank());
-    for (auto it : llvm::enumerate(type.getShape())) {
+    for (const auto &it : llvm::enumerate(type.getShape())) {
       if (it.value() == resultTy.getDimSize(it.index())) {
         newShape.push_back(it.value());
         affineExprs.push_back(
@@ -1716,7 +1716,7 @@
     SmallVector<AffineExpr, 2> inputExprs;
     inputExprs.resize(resultTy.getRank());
     auto operandTy = input.getType().cast<ShapedType>();
-    for (auto permutation : llvm::enumerate(perms.getValues<APInt>())) {
+    for (const auto &permutation : llvm::enumerate(perms.getValues<APInt>())) {
       auto index = permutation.index();
       auto value = permutation.value().getZExtValue();
       if (!operandTy.hasRank() || operandTy.isDynamicDim(index)) {
diff --git a/mlir/lib/Conversion/VectorToGPU/VectorToGPU.cpp b/mlir/lib/Conversion/VectorToGPU/VectorToGPU.cpp
--- a/mlir/lib/Conversion/VectorToGPU/VectorToGPU.cpp
+++ b/mlir/lib/Conversion/VectorToGPU/VectorToGPU.cpp
@@ -451,7 +451,7 @@
                          llvm::DenseMap<Value, Value> &valueMapping) {
   SmallVector<Value> newOperands;
   SmallVector<std::pair<size_t, size_t>> argMapping;
-  for (auto operand : llvm::enumerate(op.getIterOperands())) {
+  for (const auto &operand : llvm::enumerate(op.getIterOperands())) {
     auto it = valueMapping.find(operand.value());
     if (it == valueMapping.end())
       continue;
@@ -476,7 +476,7 @@
   OpBuilder b(op);
   auto loop = cast<scf::ForOp>(op->getParentOp());
   auto yieldOperands = llvm::to_vector<4>(op.getOperands());
-  for (auto operand : llvm::enumerate(op.getOperands())) {
+  for (const auto &operand : llvm::enumerate(op.getOperands())) {
     auto it = valueMapping.find(operand.value());
     if (it == valueMapping.end())
       continue;
diff --git a/mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVM.cpp b/mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVM.cpp
--- a/mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVM.cpp
+++ b/mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVM.cpp
@@ -497,7 +497,7 @@
       eltType = llvmType.cast<VectorType>().getElementType();
     Value insert = rewriter.create<LLVM::UndefOp>(loc, llvmType);
     int64_t insPos = 0;
-    for (auto en : llvm::enumerate(maskArrayAttr)) {
+    for (const auto &en : llvm::enumerate(maskArrayAttr)) {
       int64_t extPos = en.value().cast<IntegerAttr>().getInt();
       Value value = adaptor.v1();
       if (extPos >= v1Dim) {
@@ -883,7 +883,8 @@
     desc.setOffset(rewriter, loc, zero);
 
     // Fill size and stride descriptors in memref.
-    for (auto indexedSize : llvm::enumerate(targetMemRefType.getShape())) {
+    for (const auto &indexedSize :
+         llvm::enumerate(targetMemRefType.getShape())) {
       int64_t index = indexedSize.index();
       auto sizeAttr =
           rewriter.getIntegerAttr(rewriter.getIndexType(), indexedSize.value());
diff --git a/mlir/lib/Dialect/Affine/IR/AffineOps.cpp b/mlir/lib/Dialect/Affine/IR/AffineOps.cpp
--- a/mlir/lib/Dialect/Affine/IR/AffineOps.cpp
+++ b/mlir/lib/Dialect/Affine/IR/AffineOps.cpp
@@ -681,7 +681,7 @@
   for (auto *container : {&dims, &syms}) {
     bool isDim = (container == &dims);
     auto &repls = isDim ? dimReplacements : symReplacements;
-    for (auto en : llvm::enumerate(*container)) {
+    for (const auto &en : llvm::enumerate(*container)) {
       Value v = en.value();
       if (!v) {
         assert(isDim ? !map->isFunctionOfDim(en.index())
diff --git a/mlir/lib/Dialect/Async/Transforms/AsyncRuntimeRefCounting.cpp b/mlir/lib/Dialect/Async/Transforms/AsyncRuntimeRefCounting.cpp
--- a/mlir/lib/Dialect/Async/Transforms/AsyncRuntimeRefCounting.cpp
+++ b/mlir/lib/Dialect/Async/Transforms/AsyncRuntimeRefCounting.cpp
@@ -418,7 +418,7 @@
         continue;
 
       // Update terminator `successor` block to `refCountingBlock`.
-      for (auto pair : llvm::enumerate(terminator->getSuccessors()))
+      for (const auto &pair : llvm::enumerate(terminator->getSuccessors()))
         if (pair.value() == successor)
           terminator->setSuccessor(refCountingBlock, pair.index());
     }
diff --git a/mlir/lib/Dialect/GPU/IR/GPUDialect.cpp b/mlir/lib/Dialect/GPU/IR/GPUDialect.cpp
--- a/mlir/lib/Dialect/GPU/IR/GPUDialect.cpp
+++ b/mlir/lib/Dialect/GPU/IR/GPUDialect.cpp
@@ -940,7 +940,7 @@
         .attachNote(function.getLoc())
         .append("return type declared here");
 
-  for (auto pair : llvm::enumerate(
+  for (const auto &pair : llvm::enumerate(
            llvm::zip(function.getType().getResults(), returnOp.operands()))) {
     Type type;
     Value operand;
diff --git a/mlir/lib/Dialect/GPU/Transforms/KernelOutlining.cpp b/mlir/lib/Dialect/GPU/Transforms/KernelOutlining.cpp
--- a/mlir/lib/Dialect/GPU/Transforms/KernelOutlining.cpp
+++ b/mlir/lib/Dialect/GPU/Transforms/KernelOutlining.cpp
@@ -54,7 +54,7 @@
   createForAllDimensions<gpu::BlockDimOp>(builder, loc, indexOps);
   // Replace the leading 12 function args with the respective thread/block index
   // operations. Iterate backwards since args are erased and indices change.
-  for (auto indexOp : enumerate(indexOps))
+  for (const auto &indexOp : enumerate(indexOps))
     map.map(firstBlock.getArgument(indexOp.index()), indexOp.value());
 }
 
@@ -173,7 +173,7 @@
   // Map arguments from gpu.launch region to the arguments of the gpu.func
   // operation.
   Block &entryBlock = outlinedFuncBody.front();
-  for (auto operand : enumerate(operands))
+  for (const auto &operand : enumerate(operands))
     map.map(operand.value(), entryBlock.getArgument(operand.index()));
 
   // Clone the region of the gpu.launch operation into the gpu.func operation.
diff --git a/mlir/lib/Dialect/GPU/Transforms/MemoryPromotion.cpp b/mlir/lib/Dialect/GPU/Transforms/MemoryPromotion.cpp
--- a/mlir/lib/Dialect/GPU/Transforms/MemoryPromotion.cpp
+++ b/mlir/lib/Dialect/GPU/Transforms/MemoryPromotion.cpp
@@ -89,7 +89,7 @@
       });
 
   // Map the innermost loops to threads in reverse order.
-  for (auto en :
+  for (const auto &en :
        llvm::enumerate(llvm::reverse(llvm::makeArrayRef(ivs).take_back(
            GPUDialect::getNumWorkgroupDimensions())))) {
     Value v = en.value();
diff --git a/mlir/lib/Dialect/LLVMIR/IR/LLVMDialect.cpp b/mlir/lib/Dialect/LLVMIR/IR/LLVMDialect.cpp
--- a/mlir/lib/Dialect/LLVMIR/IR/LLVMDialect.cpp
+++ b/mlir/lib/Dialect/LLVMIR/IR/LLVMDialect.cpp
@@ -1484,7 +1484,7 @@
 // list is parsed, returns -1.
 static int parseOptionalKeywordAlternative(OpAsmParser &parser,
                                            ArrayRef<StringRef> keywords) {
-  for (auto en : llvm::enumerate(keywords)) {
+  for (const auto &en : llvm::enumerate(keywords)) {
     if (succeeded(parser.parseOptionalKeyword(en.value())))
       return en.index();
   }
diff --git a/mlir/lib/Dialect/Linalg/Analysis/DependenceAnalysis.cpp b/mlir/lib/Dialect/Linalg/Analysis/DependenceAnalysis.cpp
--- a/mlir/lib/Dialect/Linalg/Analysis/DependenceAnalysis.cpp
+++ b/mlir/lib/Dialect/Linalg/Analysis/DependenceAnalysis.cpp
@@ -103,7 +103,7 @@
 LinalgDependenceGraph::LinalgDependenceGraph(Aliases &aliases,
                                              ArrayRef<LinalgOp> ops)
     : aliases(aliases), linalgOps(ops.begin(), ops.end()) {
-  for (auto en : llvm::enumerate(linalgOps)) {
+  for (const auto &en : llvm::enumerate(linalgOps)) {
     linalgOpPositions.insert(
         std::make_pair(en.value().getOperation(), en.index()));
   }
diff --git a/mlir/lib/Dialect/Linalg/IR/LinalgOps.cpp b/mlir/lib/Dialect/Linalg/IR/LinalgOps.cpp
--- a/mlir/lib/Dialect/Linalg/IR/LinalgOps.cpp
+++ b/mlir/lib/Dialect/Linalg/IR/LinalgOps.cpp
@@ -1093,7 +1093,7 @@
     return op.emitError("expected the block to have ") << rank << " arguments";
 
   // Note: the number and type of yield values are checked in the YieldOp.
-  for (auto en : llvm::enumerate(block.getArgumentTypes())) {
+  for (const auto &en : llvm::enumerate(block.getArgumentTypes())) {
     if (!en.value().isIndex())
       return op.emitOpError("expected block argument ")
              << (en.index() + 1) << " to be an index";
@@ -1204,7 +1204,7 @@
   SmallVector<OpFoldResult, 4> low, high;
   auto rankedTensorType = type.cast<RankedTensorType>();
   assert(rankedTensorType.hasStaticShape());
-  for (auto en : enumerate(rankedTensorType.getShape())) {
+  for (const auto &en : enumerate(rankedTensorType.getShape())) {
     AffineExpr d0;
     bindDims(b.getContext(), d0);
     auto dimOp = b.createOrFold<tensor::DimOp>(loc, source, en.index());
@@ -1275,7 +1275,7 @@
   // Initialize all the ranges to {zero, one, one}. All the `ub`s are
   // overwritten.
   SmallVector<Range> loopRanges(reifiedShapes[0].size(), {zero, one, one});
-  for (auto ub : enumerate(reifiedShapes[0]))
+  for (const auto &ub : enumerate(reifiedShapes[0]))
     loopRanges[ub.index()].size = ub.value();
   return loopRanges;
 }
@@ -2001,7 +2001,7 @@
     // Store ids of the corresponding old and new input operands.
     SmallVector<int64_t, 2> oldInputIdToNew(tiledLoop.inputs().size(),
                                             kNoMatch);
-    for (auto en : llvm::enumerate(
+    for (const auto &en : llvm::enumerate(
              llvm::zip(tiledLoop.inputs(), tiledLoop.getRegionInputArgs()))) {
       Value in, bbArg;
       size_t index = en.index();
@@ -2215,7 +2215,7 @@
     SmallVector<int64_t, 2> oldResultIdToNew(tiledLoop.getNumResults(),
                                              kNoMatch);
     SmallVector<Value, 2> resultReplacement(tiledLoop.getNumResults());
-    for (auto en : llvm::enumerate(
+    for (const auto &en : llvm::enumerate(
              llvm::zip(tiledLoop.outputs(), tiledLoop.getRegionOutputArgs()))) {
       size_t index = en.index();
       Value out = std::get<0>(en.value());
diff --git a/mlir/lib/Dialect/Linalg/Transforms/Bufferize.cpp b/mlir/lib/Dialect/Linalg/Transforms/Bufferize.cpp
--- a/mlir/lib/Dialect/Linalg/Transforms/Bufferize.cpp
+++ b/mlir/lib/Dialect/Linalg/Transforms/Bufferize.cpp
@@ -43,7 +43,7 @@
 
   // Allocate a buffer for every tensor result.
   assert(linalgOp.getNumOutputs() == linalgOp->getNumResults());
-  for (auto en : llvm::enumerate(linalgOp->getResultTypes())) {
+  for (const auto &en : llvm::enumerate(linalgOp->getResultTypes())) {
     size_t resultIndex = en.index();
     Type resultType = en.value();
 
diff --git a/mlir/lib/Dialect/Linalg/Transforms/DropUnitDims.cpp b/mlir/lib/Dialect/Linalg/Transforms/DropUnitDims.cpp
--- a/mlir/lib/Dialect/Linalg/Transforms/DropUnitDims.cpp
+++ b/mlir/lib/Dialect/Linalg/Transforms/DropUnitDims.cpp
@@ -186,7 +186,7 @@
     DenseSet<unsigned> unitDims;
     SmallVector<unsigned, 4> unitDimsReductionLoops;
     ArrayAttr iteratorTypes = genericOp.iterator_types();
-    for (auto expr : enumerate(invertedMap.getResults())) {
+    for (const auto &expr : enumerate(invertedMap.getResults())) {
       if (AffineDimExpr dimExpr = expr.value().dyn_cast<AffineDimExpr>())
         if (dims[dimExpr.getPosition()] == 1)
           unitDims.insert(expr.index());
@@ -205,7 +205,7 @@
     // Compute the iterator types of the modified op by dropping the one-trip
     // count loops.
     SmallVector<Attribute, 4> newIteratorTypes;
-    for (auto attr : llvm::enumerate(iteratorTypes)) {
+    for (const auto &attr : llvm::enumerate(iteratorTypes)) {
       if (!unitDims.count(attr.index()))
         newIteratorTypes.push_back(attr.value());
     }
@@ -439,7 +439,7 @@
     // If any result tensor has a modified shape, then add reshape to recover
     // the original shape.
     SmallVector<Value, 4> resultReplacements;
-    for (auto result : llvm::enumerate(replacementOp.getResults())) {
+    for (const auto &result : llvm::enumerate(replacementOp.getResults())) {
       unsigned index = result.index() + replacementOp.getNumInputs();
       auto origResultType = genericOp.getResult(result.index()).getType();
 
@@ -465,7 +465,7 @@
 getReassociationMapForFoldingUnitDims(ArrayRef<OpFoldResult> mixedSizes) {
   SmallVector<ReassociationIndices> reassociation;
   ReassociationIndices curr;
-  for (auto it : llvm::enumerate(mixedSizes)) {
+  for (const auto &it : llvm::enumerate(mixedSizes)) {
     auto dim = it.index();
     auto size = it.value();
     curr.push_back(dim);
diff --git a/mlir/lib/Dialect/Linalg/Transforms/ElementwiseOpFusion.cpp b/mlir/lib/Dialect/Linalg/Transforms/ElementwiseOpFusion.cpp
--- a/mlir/lib/Dialect/Linalg/Transforms/ElementwiseOpFusion.cpp
+++ b/mlir/lib/Dialect/Linalg/Transforms/ElementwiseOpFusion.cpp
@@ -563,7 +563,7 @@
   // dimension of the original op.
   SmallVector<unsigned> numExpandedDims(fusedIndexMap.getNumDims(), 1);
   expandedShapeMap.resize(fusedIndexMap.getNumDims());
-  for (auto resultExpr : llvm::enumerate(fusedIndexMap.getResults())) {
+  for (const auto &resultExpr : llvm::enumerate(fusedIndexMap.getResults())) {
     unsigned pos = resultExpr.value().cast<AffineDimExpr>().getPosition();
     AffineMap foldedDims = reassociationMaps[resultExpr.index()];
     numExpandedDims[pos] = foldedDims.getNumResults();
@@ -579,7 +579,7 @@
   // Compute reassociation map from the original op to the expanded op.
   unsigned sum = 0;
   reassociation.reserve(fusedIndexMap.getNumDims());
-  for (auto numFoldedDim : llvm::enumerate(numExpandedDims)) {
+  for (const auto &numFoldedDim : llvm::enumerate(numExpandedDims)) {
     auto seq = llvm::seq<int64_t>(sum, sum + numFoldedDim.value());
     reassociation.emplace_back(seq.begin(), seq.end());
     sum += numFoldedDim.value();
@@ -859,7 +859,7 @@
     if (!genericOp.hasTensorSemantics())
       return failure();
     SmallVector<OpOperand *> inputOperands = genericOp.getInputOperands();
-    for (auto en : llvm::enumerate(inputOperands)) {
+    for (const auto &en : llvm::enumerate(inputOperands)) {
       auto reshapeOp = en.value()->get().getDefiningOp<TensorReshapeOp>();
       if (!reshapeOp)
         continue;
@@ -974,7 +974,7 @@
     // 1. Look for tensor_expand_shape operands and figure out save the
     // dimensions merged.
     SmallVector<OpOperand *> inputOperands = genericOp.getInputOperands();
-    for (auto en : llvm::enumerate(inputOperands)) {
+    for (const auto &en : llvm::enumerate(inputOperands)) {
       auto reshapeOp =
           en.value()->get().template getDefiningOp<tensor::ExpandShapeOp>();
       if (!reshapeOp)
@@ -1008,7 +1008,7 @@
     // 2. Verify that we can merge the dimensions in the linalg and that we
     // don't need to create new reshapes operands. Inserting new reshape
     // operands would defeat the purpose of the transformation.
-    for (auto en : llvm::enumerate(inputOperands)) {
+    for (const auto &en : llvm::enumerate(inputOperands)) {
       if (en.value()->get() == newOperands[en.index()]) {
         AffineMap map = genericOp.getTiedIndexingMap(en.value());
         for (unsigned i : llvm::seq(unsigned(0), map.getNumResults())) {
@@ -1058,7 +1058,7 @@
                                 newOp.region().begin());
     // 6. Reshape the so that the type matches the uses.
     SmallVector<Value> newResults;
-    for (auto result : llvm::enumerate(newOp->getResults())) {
+    for (const auto &result : llvm::enumerate(newOp->getResults())) {
       newResults.push_back(rewriter.create<tensor::ExpandShapeOp>(
           genericOp->getLoc(), genericOp.getOutputTensorTypes()[result.index()],
           result.value(), reassociation));
@@ -1405,7 +1405,7 @@
     // All inputs should be constants.
     int numInputs = genericOp.getNumInputs();
     SmallVector<DenseIntOrFPElementsAttr> inputValues(numInputs);
-    for (auto operand : llvm::enumerate(genericOp.getInputOperands())) {
+    for (const auto &operand : llvm::enumerate(genericOp.getInputOperands())) {
       if (!matchPattern(operand.value()->get(),
                         m_Constant(&inputValues[operand.index()])))
         return failure();
@@ -1710,7 +1710,7 @@
           continue;
         modifiedOutput = true;
         SmallVector<Value> dynamicDims;
-        for (auto dim : llvm::enumerate(operandType.getShape())) {
+        for (const auto &dim : llvm::enumerate(operandType.getShape())) {
           if (dim.value() != ShapedType::kDynamicSize)
             continue;
           dynamicDims.push_back(rewriter.createOrFold<tensor::DimOp>(
diff --git a/mlir/lib/Dialect/Linalg/Transforms/Fusion.cpp b/mlir/lib/Dialect/Linalg/Transforms/Fusion.cpp
--- a/mlir/lib/Dialect/Linalg/Transforms/Fusion.cpp
+++ b/mlir/lib/Dialect/Linalg/Transforms/Fusion.cpp
@@ -89,7 +89,7 @@
     LLVM_DEBUG(llvm::dbgs()
                << "getShapeDefiningLoopRange map: " << map << "\n");
     SmallVector<Value, 8> shapeRanges(map.getNumResults(), nullptr);
-    for (auto en : llvm::enumerate(map.getResults())) {
+    for (const auto &en : llvm::enumerate(map.getResults())) {
       auto dimExpr = en.value().dyn_cast<AffineDimExpr>();
       if (!dimExpr)
         continue;
@@ -252,7 +252,7 @@
   LLVM_DEBUG(llvm::dbgs() << "Producer map: " << producerMap << "\n");
   DenseMap<unsigned, Range> fusedLoopsAndRanges;
   Value shapedOperand = consumerOpOperand.get();
-  for (auto en : llvm::enumerate(producerMap.getResults())) {
+  for (const auto &en : llvm::enumerate(producerMap.getResults())) {
     unsigned posInProducerLoop = en.value().cast<AffineDimExpr>().getPosition();
     fusedLoopsAndRanges[posInProducerLoop] = getRangeFromOperandShape(
         b, consumerOpOperand.getOwner()->getLoc(), shapedOperand, en.index());
@@ -523,7 +523,7 @@
 static AffineMap pruneReductionDimsFromMap(ArrayRef<Attribute> iteratorTypes,
                                            AffineMap map) {
   llvm::SmallDenseSet<unsigned> projectedDims;
-  for (auto attr : llvm::enumerate(iteratorTypes)) {
+  for (const auto &attr : llvm::enumerate(iteratorTypes)) {
     if (!isParallelIterator(attr.value()))
       projectedDims.insert(attr.index());
   }
@@ -812,7 +812,7 @@
   SmallVector<LinalgOp, 1> fusedOps(fusionCandidates.size());
   DenseMap<Operation *, LinalgOp> origOpToFusedOp;
   origOpToFusedOp[rootOp.getOperation()] = tiledOp;
-  for (auto candidate : enumerate(llvm::reverse(fusionCandidates))) {
+  for (const auto &candidate : enumerate(llvm::reverse(fusionCandidates))) {
     LinalgOp origOp = candidate.value();
     LinalgOp fusedOp = fuse(b, origOp, fusedLoopsAndRanges);
     origOpToFusedOp[origOp.getOperation()] = fusedOp;
diff --git a/mlir/lib/Dialect/Linalg/Transforms/FusionOnTensors.cpp b/mlir/lib/Dialect/Linalg/Transforms/FusionOnTensors.cpp
--- a/mlir/lib/Dialect/Linalg/Transforms/FusionOnTensors.cpp
+++ b/mlir/lib/Dialect/Linalg/Transforms/FusionOnTensors.cpp
@@ -42,7 +42,7 @@
 
   // Search the slice dimensions tiled by a tile loop dimension.
   DenseSet<int64_t> tiledSliceDimIndices;
-  for (auto en : enumerate(indexingMap.getResults())) {
+  for (const auto &en : enumerate(indexingMap.getResults())) {
     for (auto tiledLoopDim : tiledLoopDims) {
       if (en.value().isFunctionOfDim(tiledLoopDim))
         tiledSliceDimIndices.insert(en.index());
@@ -304,7 +304,7 @@
   // Update the root operation and append the loops and tile loop dimensions.
   rootOp = tiledRootOp->op;
   tileLoopOps.append(tiledRootOp->loops.begin(), tiledRootOp->loops.end());
-  for (auto en : enumerate(tileSizes)) {
+  for (const auto &en : enumerate(tileSizes)) {
     // Copy only the tiled loop dimensions with non-zero tile size.
     if (en.value() == 0)
       continue;
diff --git a/mlir/lib/Dialect/Linalg/Transforms/Hoisting.cpp b/mlir/lib/Dialect/Linalg/Transforms/Hoisting.cpp
--- a/mlir/lib/Dialect/Linalg/Transforms/Hoisting.cpp
+++ b/mlir/lib/Dialect/Linalg/Transforms/Hoisting.cpp
@@ -346,7 +346,7 @@
     changed = false;
     func.walk([&](scf::ForOp forOp) {
       Operation *yield = forOp.getBody()->getTerminator();
-      for (auto it : llvm::enumerate(forOp.getRegionIterArgs())) {
+      for (const auto &it : llvm::enumerate(forOp.getRegionIterArgs())) {
         OpOperand &ret = yield->getOpOperand(it.index());
         HoistableWrite write =
             getLoopInvariantTransferWriteOpDefining(forOp, ret);
diff --git a/mlir/lib/Dialect/Linalg/Transforms/Loops.cpp b/mlir/lib/Dialect/Linalg/Transforms/Loops.cpp
--- a/mlir/lib/Dialect/Linalg/Transforms/Loops.cpp
+++ b/mlir/lib/Dialect/Linalg/Transforms/Loops.cpp
@@ -277,7 +277,7 @@
     // Collect loop control parameters for parallel and sequential dimensions.
     SmallVector<Value, 3> seqLBs, seqUBs, seqSteps, seqIVs;
     SmallVector<Value, 3> parLBs, parUBs, parSteps, parIVs;
-    for (auto en : llvm::enumerate(
+    for (const auto &en : llvm::enumerate(
              llvm::zip(tiledLoop.lowerBound(), tiledLoop.upperBound(),
                        tiledLoop.step(), tiledLoop.getInductionVars()))) {
       Value lb, ub, step, iv;
diff --git a/mlir/lib/Dialect/Linalg/Transforms/Promotion.cpp b/mlir/lib/Dialect/Linalg/Transforms/Promotion.cpp
--- a/mlir/lib/Dialect/Linalg/Transforms/Promotion.cpp
+++ b/mlir/lib/Dialect/Linalg/Transforms/Promotion.cpp
@@ -87,7 +87,7 @@
   auto one = b.createOrFold<arith::ConstantIndexOp>(1);
 
   Value allocSize = one;
-  for (auto size : llvm::enumerate(boundingSubViewSize))
+  for (const auto &size : llvm::enumerate(boundingSubViewSize))
     allocSize = b.createOrFold<arith::MulIOp>(allocSize, size.value());
   Value buffer = allocBuffer(b, options, viewType.getElementType(), allocSize,
                              layout, alignment);
@@ -219,7 +219,7 @@
   SmallVector<OpFoldResult> partialSizes;
   fullSizes.reserve(rank);
   partialSizes.reserve(rank);
-  for (auto en : llvm::enumerate(subView.getOrCreateRanges(b, loc))) {
+  for (const auto &en : llvm::enumerate(subView.getOrCreateRanges(b, loc))) {
     auto rangeValue = en.value();
     // Try to extract a tight constant.
     LLVM_DEBUG(llvm::dbgs() << "Extract tightest: " << rangeValue.size << "\n");
diff --git a/mlir/lib/Dialect/Linalg/Transforms/Tiling.cpp b/mlir/lib/Dialect/Linalg/Transforms/Tiling.cpp
--- a/mlir/lib/Dialect/Linalg/Transforms/Tiling.cpp
+++ b/mlir/lib/Dialect/Linalg/Transforms/Tiling.cpp
@@ -179,7 +179,7 @@
       b, op.getLoc(), shapeSizesToLoopsMap, allShapeSizes, tileSizes);
 
   SmallVector<Attribute, 4> iteratorTypes;
-  for (auto attr :
+  for (const auto &attr :
        enumerate(op.iterator_types().cast<ArrayAttr>().getValue())) {
     if (loopIndexToRangeIndex.count(attr.index()))
       iteratorTypes.push_back(attr.value());
diff --git a/mlir/lib/Dialect/Linalg/Transforms/Transforms.cpp b/mlir/lib/Dialect/Linalg/Transforms/Transforms.cpp
--- a/mlir/lib/Dialect/Linalg/Transforms/Transforms.cpp
+++ b/mlir/lib/Dialect/Linalg/Transforms/Transforms.cpp
@@ -193,7 +193,7 @@
   SmallVector<int64_t> staticSizes;
   staticSizes.reserve(shape.size());
   auto shapedOp = cast<OffsetSizeAndStrideOpInterface>(sliceOp.getOperation());
-  for (auto en : enumerate(shapedOp.getMixedSizes())) {
+  for (const auto &en : enumerate(shapedOp.getMixedSizes())) {
     // Skip dropped dimensions.
     if (droppedDims.contains(en.index()))
       continue;
@@ -268,7 +268,7 @@
   // linalg op around because it uses the dims of the original results.
   SmallVector<Value> paddedSubviewResults;
   paddedSubviewResults.reserve(opToPad->getNumResults());
-  for (auto en : llvm::enumerate(paddedOp->getResults())) {
+  for (const auto &en : llvm::enumerate(paddedOp->getResults())) {
     Value paddedResult = en.value();
     int64_t resultNumber = en.index();
     int64_t rank = paddedResult.getType().cast<RankedTensorType>().getRank();
@@ -441,7 +441,7 @@
   // Tile the unfused loops;
   SmallVector<Value, 4> unfusedLoopTileSizes;
   Value zero = rewriter.create<arith::ConstantIndexOp>(op->getLoc(), 0);
-  for (auto tileSize : enumerate(tileSizes)) {
+  for (const auto &tileSize : enumerate(tileSizes)) {
     if (tiledAndFusedOps->fusedLoopDims.count(tileSize.index()))
       unfusedLoopTileSizes.push_back(zero);
     else
@@ -522,7 +522,7 @@
   }
 
   // Hoist the padding.
-  for (auto en : enumerate(depths)) {
+  for (const auto &en : enumerate(depths)) {
     OpOperand &opOperand = paddedOp->getOpOperand(en.index());
     auto padTensorOp = opOperand.get().getDefiningOp<PadTensorOp>();
     if (!padTensorOp || en.value() == 0)
diff --git a/mlir/lib/Dialect/Linalg/Transforms/Vectorization.cpp b/mlir/lib/Dialect/Linalg/Transforms/Vectorization.cpp
--- a/mlir/lib/Dialect/Linalg/Transforms/Vectorization.cpp
+++ b/mlir/lib/Dialect/Linalg/Transforms/Vectorization.cpp
@@ -256,7 +256,7 @@
   auto yieldOp = dyn_cast<linalg::YieldOp>(op);
   if (!yieldOp)
     return VectorizationResult{VectorizationStatus::Failure, nullptr};
-  for (auto outputs : llvm::enumerate(yieldOp.values())) {
+  for (const auto &outputs : llvm::enumerate(yieldOp.values())) {
     // TODO: Scan for an opportunity for reuse.
     // TODO: use a map.
     Value vectorValue = bvm.lookup(outputs.value());
diff --git a/mlir/lib/Dialect/Linalg/Utils/Utils.cpp b/mlir/lib/Dialect/Linalg/Utils/Utils.cpp
--- a/mlir/lib/Dialect/Linalg/Utils/Utils.cpp
+++ b/mlir/lib/Dialect/Linalg/Utils/Utils.cpp
@@ -169,7 +169,7 @@
 SmallVector<Value, 4> getDynOperands(Location loc, Value val, OpBuilder &b) {
   SmallVector<Value, 4> dynOperands;
   auto shapedType = val.getType().cast<ShapedType>();
-  for (auto dim : llvm::enumerate(shapedType.getShape())) {
+  for (const auto &dim : llvm::enumerate(shapedType.getShape())) {
     if (dim.value() == ShapedType::kDynamicSize)
       dynOperands.push_back(createOrFoldDimOp(b, loc, val, dim.index()));
   }
@@ -310,7 +310,7 @@
   SmallVector<OpFoldResult> foldedOffsets(offsets.begin(), offsets.end());
   AffineExpr dim1, dim2;
   bindDims(b.getContext(), dim1, dim2);
-  for (auto en : enumerate(producerOp.getMixedOffsets())) {
+  for (const auto &en : enumerate(producerOp.getMixedOffsets())) {
     SmallVector<Value> offsetValues = {
         getValueOrCreateConstantIndexOp(b, loc, foldedOffsets[en.index()]),
         getValueOrCreateConstantIndexOp(b, loc, en.value())};
@@ -403,7 +403,7 @@
   if (distributionOptions.hasValue()) {
     // Collect loop ranges for parallel dimensions.
     SmallVector<Range, 2> parallelLoopRanges;
-    for (auto iteratorType : enumerate(iteratorTypes))
+    for (const auto &iteratorType : enumerate(iteratorTypes))
       if (isParallelIterator(iteratorType.value()))
         parallelLoopRanges.push_back(loopRanges[iteratorType.index()]);
 
@@ -435,7 +435,7 @@
 
   // Filter out scf.for loops that were created out of parallel dimensions.
   SmallVector<scf::ForOp, 4> loops;
-  for (auto iteratorType : enumerate(iteratorTypes))
+  for (const auto &iteratorType : enumerate(iteratorTypes))
     if (isParallelIterator(iteratorType.value()))
       loops.push_back(loopNest.loops[iteratorType.index()]);
 
@@ -677,7 +677,7 @@
     distributionMethod.assign(distributionOptions->distributionMethod.begin(),
                               distributionOptions->distributionMethod.end());
     SmallVector<Range, 2> parallelLoopRanges;
-    for (auto iteratorType : enumerate(iteratorTypes)) {
+    for (const auto &iteratorType : enumerate(iteratorTypes)) {
       if (isParallelIterator(iteratorType.value()))
         parallelLoopRanges.push_back(loopRanges[iteratorType.index()]);
     }
@@ -686,7 +686,7 @@
     SmallVector<ProcInfo, 2> procInfo =
         options.procInfo(b, loc, parallelLoopRanges);
     unsigned index = 0;
-    for (auto iteratorType : enumerate(iteratorTypes)) {
+    for (const auto &iteratorType : enumerate(iteratorTypes)) {
       if (index >= procInfo.size())
         break;
       if (isParallelIterator(iteratorType.value())) {
diff --git a/mlir/lib/Dialect/Math/Transforms/PolynomialApproximation.cpp b/mlir/lib/Dialect/Math/Transforms/PolynomialApproximation.cpp
--- a/mlir/lib/Dialect/Math/Transforms/PolynomialApproximation.cpp
+++ b/mlir/lib/Dialect/Math/Transforms/PolynomialApproximation.cpp
@@ -134,7 +134,7 @@
     auto offsets = delinearize(strides, i);
 
     SmallVector<Value> extracted(expandedOperands.size());
-    for (auto tuple : llvm::enumerate(expandedOperands))
+    for (const auto &tuple : llvm::enumerate(expandedOperands))
       extracted[tuple.index()] =
           builder.create<vector::ExtractOp>(tuple.value(), offsets);
 
diff --git a/mlir/lib/Dialect/MemRef/IR/MemRefOps.cpp b/mlir/lib/Dialect/MemRef/IR/MemRefOps.cpp
--- a/mlir/lib/Dialect/MemRef/IR/MemRefOps.cpp
+++ b/mlir/lib/Dialect/MemRef/IR/MemRefOps.cpp
@@ -395,7 +395,7 @@
       };
       if (!checkCompatible(aOffset, bOffset))
         return false;
-      for (auto aStride : enumerate(aStrides))
+      for (const auto &aStride : enumerate(aStrides))
         if (!checkCompatible(aStride.value(), bStrides[aStride.index()]))
           return false;
     }
@@ -518,7 +518,7 @@
   if (originalType.getRank() == reducedType.getRank())
     return unusedDims;
 
-  for (auto dim : llvm::enumerate(sizes))
+  for (const auto &dim : llvm::enumerate(sizes))
     if (auto attr = dim.value().dyn_cast<Attribute>())
       if (attr.cast<IntegerAttr>().getInt() == 1)
         unusedDims.insert(dim.index());
@@ -1869,7 +1869,7 @@
   if (!unusedDims)
     return nullptr;
   SmallVector<int64_t> shape;
-  for (auto sizes : llvm::enumerate(nonRankReducedType.getShape())) {
+  for (const auto &sizes : llvm::enumerate(nonRankReducedType.getShape())) {
     if (unusedDims->count(sizes.index()))
       continue;
     shape.push_back(sizes.value());
@@ -2001,7 +2001,7 @@
   auto originalSizes = memRefType.getShape();
   // Compute permuted sizes.
   SmallVector<int64_t, 4> sizes(rank, 0);
-  for (auto en : llvm::enumerate(permutationMap.getResults()))
+  for (const auto &en : llvm::enumerate(permutationMap.getResults()))
     sizes[en.index()] =
         originalSizes[en.value().cast<AffineDimExpr>().getPosition()];
 
diff --git a/mlir/lib/Dialect/OpenMP/IR/OpenMPDialect.cpp b/mlir/lib/Dialect/OpenMP/IR/OpenMPDialect.cpp
--- a/mlir/lib/Dialect/OpenMP/IR/OpenMPDialect.cpp
+++ b/mlir/lib/Dialect/OpenMP/IR/OpenMPDialect.cpp
@@ -249,7 +249,7 @@
                         SmallVectorImpl<SmallString<12>> &modifiers) {
   if (modifiers.size() > 2)
     return parser.emitError(parser.getNameLoc()) << " unexpected modifier(s)";
-  for (auto mod : modifiers) {
+  for (const auto &mod : modifiers) {
     // Translate the string. If it has no value, then it was not a valid
     // modifier!
     auto symbol = symbolizeScheduleModifier(mod);
diff --git a/mlir/lib/Dialect/PDL/IR/PDL.cpp b/mlir/lib/Dialect/PDL/IR/PDL.cpp
--- a/mlir/lib/Dialect/PDL/IR/PDL.cpp
+++ b/mlir/lib/Dialect/PDL/IR/PDL.cpp
@@ -198,7 +198,7 @@
     return success();
 
   // Otherwise, make sure each of the types can be inferred.
-  for (auto it : llvm::enumerate(resultTypes)) {
+  for (const auto &it : llvm::enumerate(resultTypes)) {
     Operation *resultTypeOp = it.value().getDefiningOp();
     assert(resultTypeOp && "expected valid result type operation");
 
diff --git a/mlir/lib/Dialect/SCF/SCF.cpp b/mlir/lib/Dialect/SCF/SCF.cpp
--- a/mlir/lib/Dialect/SCF/SCF.cpp
+++ b/mlir/lib/Dialect/SCF/SCF.cpp
@@ -1248,7 +1248,7 @@
 
     // Replace the operation by the new one.
     SmallVector<Value, 4> repResults(op.getNumResults());
-    for (auto en : llvm::enumerate(usedResults))
+    for (const auto &en : llvm::enumerate(usedResults))
       repResults[en.value().getResultNumber()] = newOp.getResult(en.index());
     rewriter.replaceOp(op, repResults);
     return success();
@@ -1297,7 +1297,8 @@
     SmallVector<Value> results(op->getNumResults());
     assert(thenYieldArgs.size() == results.size());
     assert(elseYieldArgs.size() == results.size());
-    for (auto it : llvm::enumerate(llvm::zip(thenYieldArgs, elseYieldArgs))) {
+    for (const auto &it :
+         llvm::enumerate(llvm::zip(thenYieldArgs, elseYieldArgs))) {
       Value trueVal = std::get<0>(it.value());
       Value falseVal = std::get<1>(it.value());
       if (trueVal == falseVal)
@@ -1565,7 +1566,7 @@
 
     SmallVector<Value> prevValues;
     SmallVector<Value> nextValues;
-    for (auto pair : llvm::enumerate(combinedIf.getResults())) {
+    for (const auto &pair : llvm::enumerate(combinedIf.getResults())) {
       if (pair.index() < prevIf.getNumResults())
         prevValues.push_back(pair.value());
       else
@@ -2369,7 +2370,7 @@
     SmallVector<Type> newResultTypes;
     SmallVector<Value> newTermArgs;
     bool needUpdate = false;
-    for (auto it :
+    for (const auto &it :
          llvm::enumerate(llvm::zip(op.getResults(), afterArgs, termArgs))) {
       auto i = static_cast<unsigned>(it.index());
       Value result = std::get<0>(it.value());
@@ -2404,7 +2405,7 @@
     // null).
     SmallVector<Value> newResults(op.getNumResults());
     SmallVector<Value> newAfterBlockArgs(op.getNumResults());
-    for (auto it : llvm::enumerate(newResultsIndices)) {
+    for (const auto &it : llvm::enumerate(newResultsIndices)) {
       newResults[it.value()] = newWhile.getResult(it.index());
       newAfterBlockArgs[it.value()] = newAfterBlock.getArgument(it.index());
     }
diff --git a/mlir/lib/Dialect/SCF/Transforms/ForToWhile.cpp b/mlir/lib/Dialect/SCF/Transforms/ForToWhile.cpp
--- a/mlir/lib/Dialect/SCF/Transforms/ForToWhile.cpp
+++ b/mlir/lib/Dialect/SCF/Transforms/ForToWhile.cpp
@@ -69,7 +69,7 @@
 
     // Rewrite uses of the for-loop block arguments to the new while-loop
     // "after" arguments
-    for (auto barg : enumerate(forOp.getBody(0)->getArguments()))
+    for (const auto &barg : enumerate(forOp.getBody(0)->getArguments()))
       barg.value().replaceAllUsesWith(afterBlock->getArgument(barg.index()));
 
     // Inline for-loop body operations into 'after' region.
@@ -87,7 +87,7 @@
     // an extra value (the induction variable escapes the loop through being
     // carried in the set of iterargs). Instead, rewrite uses of the forOp
     // results.
-    for (auto arg : llvm::enumerate(forOp.getResults()))
+    for (const auto &arg : llvm::enumerate(forOp.getResults()))
       arg.value().replaceAllUsesWith(whileOp.getResult(arg.index() + 1));
 
     rewriter.eraseOp(forOp);
diff --git a/mlir/lib/Dialect/SCF/Transforms/LoopPipelining.cpp b/mlir/lib/Dialect/SCF/Transforms/LoopPipelining.cpp
--- a/mlir/lib/Dialect/SCF/Transforms/LoopPipelining.cpp
+++ b/mlir/lib/Dialect/SCF/Transforms/LoopPipelining.cpp
@@ -198,7 +198,7 @@
   llvm::SmallVector<Value> newLoopArg;
   // For existing loop argument initialize them with the right version from the
   // prologue.
-  for (auto retVal :
+  for (const auto &retVal :
        llvm::enumerate(forOp.getBody()->getTerminator()->getOperands())) {
     Operation *def = retVal.value().getDefiningOp();
     assert(def && "Only support loop carried dependencies of distance 1");
@@ -245,7 +245,7 @@
   rewriter.setInsertionPoint(newForOp.getBody(), newForOp.getBody()->begin());
   BlockAndValueMapping mapping;
   mapping.map(forOp.getInductionVar(), newForOp.getInductionVar());
-  for (auto arg : llvm::enumerate(forOp.getRegionIterArgs())) {
+  for (const auto &arg : llvm::enumerate(forOp.getRegionIterArgs())) {
     mapping.map(arg.value(), newForOp.getRegionIterArgs()[arg.index()]);
   }
   for (Operation *op : opOrder) {
@@ -325,7 +325,7 @@
     yieldOperands.push_back(mapping.lookupOrDefault(it.first));
   }
   // Map the yield operand to the forOp returned value.
-  for (auto retVal :
+  for (const auto &retVal :
        llvm::enumerate(forOp.getBody()->getTerminator()->getOperands())) {
     Operation *def = retVal.value().getDefiningOp();
     assert(def && "Only support loop carried dependencies of distance 1");
diff --git a/mlir/lib/Dialect/SCF/Transforms/ParallelLoopTiling.cpp b/mlir/lib/Dialect/SCF/Transforms/ParallelLoopTiling.cpp
--- a/mlir/lib/Dialect/SCF/Transforms/ParallelLoopTiling.cpp
+++ b/mlir/lib/Dialect/SCF/Transforms/ParallelLoopTiling.cpp
@@ -160,8 +160,8 @@
     ifInbound.getThenRegion().takeBody(op.getRegion());
     Block &thenBlock = ifInbound.getThenRegion().front();
     b.setInsertionPointToStart(innerLoop.getBody());
-    for (auto ivs : llvm::enumerate(llvm::zip(innerLoop.getInductionVars(),
-                                              outerLoop.getInductionVars()))) {
+    for (const auto &ivs : llvm::enumerate(llvm::zip(
+             innerLoop.getInductionVars(), outerLoop.getInductionVars()))) {
       auto newIndex = b.create<arith::AddIOp>(
           op.getLoc(), std::get<0>(ivs.value()), std::get<1>(ivs.value()));
       thenBlock.getArgument(ivs.index())
diff --git a/mlir/lib/Dialect/SPIRV/Transforms/LowerABIAttributesPass.cpp b/mlir/lib/Dialect/SPIRV/Transforms/LowerABIAttributesPass.cpp
--- a/mlir/lib/Dialect/SPIRV/Transforms/LowerABIAttributesPass.cpp
+++ b/mlir/lib/Dialect/SPIRV/Transforms/LowerABIAttributesPass.cpp
@@ -182,7 +182,7 @@
   auto indexType = typeConverter.getIndexType();
 
   auto attrName = spirv::getInterfaceVarABIAttrName();
-  for (auto argType : llvm::enumerate(funcOp.getType().getInputs())) {
+  for (const auto &argType : llvm::enumerate(funcOp.getType().getInputs())) {
     auto abiInfo = funcOp.getArgAttrOfType<spirv::InterfaceVarABIAttr>(
         argType.index(), attrName);
     if (!abiInfo) {
diff --git a/mlir/lib/Dialect/SPIRV/Transforms/SPIRVConversion.cpp b/mlir/lib/Dialect/SPIRV/Transforms/SPIRVConversion.cpp
--- a/mlir/lib/Dialect/SPIRV/Transforms/SPIRVConversion.cpp
+++ b/mlir/lib/Dialect/SPIRV/Transforms/SPIRVConversion.cpp
@@ -235,7 +235,7 @@
       return llvm::None;
 
     int64_t memrefSize = -1;
-    for (auto shape : enumerate(dims))
+    for (const auto &shape : enumerate(dims))
       memrefSize = std::max(memrefSize, shape.value() * strides[shape.index()]);
 
     return (offset + memrefSize) * elementSize.getValue();
@@ -557,7 +557,7 @@
     return failure();
 
   TypeConverter::SignatureConversion signatureConverter(fnType.getNumInputs());
-  for (auto argType : enumerate(fnType.getInputs())) {
+  for (const auto &argType : enumerate(fnType.getInputs())) {
     auto convertedType = getTypeConverter()->convertType(argType.value());
     if (!convertedType)
       return failure();
@@ -777,7 +777,7 @@
 
   Value linearizedIndex = builder.create<spirv::ConstantOp>(
       loc, integerType, IntegerAttr::get(integerType, offset));
-  for (auto index : llvm::enumerate(indices)) {
+  for (const auto &index : llvm::enumerate(indices)) {
     Value strideVal = builder.create<spirv::ConstantOp>(
         loc, integerType,
         IntegerAttr::get(integerType, strides[index.index()]));
diff --git a/mlir/lib/Dialect/Shape/IR/Shape.cpp b/mlir/lib/Dialect/Shape/IR/Shape.cpp
--- a/mlir/lib/Dialect/Shape/IR/Shape.cpp
+++ b/mlir/lib/Dialect/Shape/IR/Shape.cpp
@@ -1669,7 +1669,7 @@
           "ReduceOp operates on an extent tensor");
   }
 
-  for (auto type : llvm::enumerate(op.getInitVals()))
+  for (const auto &type : llvm::enumerate(op.getInitVals()))
     if (block.getArgument(type.index() + 2).getType() != type.value().getType())
       return op.emitOpError()
              << "type mismatch between argument " << type.index() + 2
diff --git a/mlir/lib/Dialect/StandardOps/Transforms/DecomposeCallGraphTypes.cpp b/mlir/lib/Dialect/StandardOps/Transforms/DecomposeCallGraphTypes.cpp
--- a/mlir/lib/Dialect/StandardOps/Transforms/DecomposeCallGraphTypes.cpp
+++ b/mlir/lib/Dialect/StandardOps/Transforms/DecomposeCallGraphTypes.cpp
@@ -67,7 +67,7 @@
 
     // Convert function arguments using the provided TypeConverter.
     TypeConverter::SignatureConversion conversion(functionType.getNumInputs());
-    for (auto argType : llvm::enumerate(functionType.getInputs())) {
+    for (const auto &argType : llvm::enumerate(functionType.getInputs())) {
       SmallVector<Type, 2> decomposedTypes;
       if (failed(typeConverter->convertType(argType.value(), decomposedTypes)))
         return failure();
diff --git a/mlir/lib/Dialect/Tensor/IR/TensorOps.cpp b/mlir/lib/Dialect/Tensor/IR/TensorOps.cpp
--- a/mlir/lib/Dialect/Tensor/IR/TensorOps.cpp
+++ b/mlir/lib/Dialect/Tensor/IR/TensorOps.cpp
@@ -1030,7 +1030,7 @@
   ArrayRef<int64_t> resultShape = getType().getShape();
   SmallVector<OpFoldResult> mixedSizes = getMixedSizes();
   unsigned shapePos = 0;
-  for (auto size : enumerate(mixedSizes)) {
+  for (const auto &size : enumerate(mixedSizes)) {
     Optional<int64_t> sizeVal = getConstantIntValue(size.value());
     // If the size is not 1, or if the current matched dimension of the result
     // is the same static shape as the size value (which is 1), then the
@@ -1052,7 +1052,7 @@
   SmallVector<OpFoldResult> mixedSizes = getMixedSizes();
   llvm::SmallDenseSet<unsigned> droppedDims = getDroppedDims();
   Location loc = getLoc();
-  for (auto size : enumerate(mixedSizes)) {
+  for (const auto &size : enumerate(mixedSizes)) {
     if (droppedDims.count(size.index()))
       continue;
     if (auto attr = size.value().dyn_cast<Attribute>()) {
diff --git a/mlir/lib/Dialect/Tosa/IR/TosaOps.cpp b/mlir/lib/Dialect/Tosa/IR/TosaOps.cpp
--- a/mlir/lib/Dialect/Tosa/IR/TosaOps.cpp
+++ b/mlir/lib/Dialect/Tosa/IR/TosaOps.cpp
@@ -1812,7 +1812,7 @@
     if (resultKnowledge.size() != yieldOp.getNumOperands())
       return failure();
 
-    for (auto it : llvm::enumerate(yieldOp.getOperands())) {
+    for (const auto &it : llvm::enumerate(yieldOp.getOperands())) {
       int32_t index = it.index();
       auto meet = ValueKnowledge::meet(
           resultKnowledge[index],
@@ -1857,7 +1857,7 @@
     if (resultKnowledge.size() != yieldOp.getNumOperands())
       return failure();
 
-    for (auto it : llvm::enumerate(yieldOp.getOperands())) {
+    for (const auto &it : llvm::enumerate(yieldOp.getOperands())) {
       int32_t index = it.index();
       if (auto meet = ValueKnowledge::meet(
               resultKnowledge[index],
diff --git a/mlir/lib/Dialect/Tosa/Transforms/TosaInferShapes.cpp b/mlir/lib/Dialect/Tosa/Transforms/TosaInferShapes.cpp
--- a/mlir/lib/Dialect/Tosa/Transforms/TosaInferShapes.cpp
+++ b/mlir/lib/Dialect/Tosa/Transforms/TosaInferShapes.cpp
@@ -132,7 +132,7 @@
     }
 
     for (auto yieldOp : yieldOps) {
-      for (auto it : llvm::enumerate(yieldOp.getOperands())) {
+      for (const auto &it : llvm::enumerate(yieldOp.getOperands())) {
         auto newKnowledge =
             ValueKnowledge::getKnowledgeFromType(it.value().getType());
         yieldTypeInfo[it.index()] =
diff --git a/mlir/lib/Dialect/Utils/ReshapeOpsUtils.cpp b/mlir/lib/Dialect/Utils/ReshapeOpsUtils.cpp
--- a/mlir/lib/Dialect/Utils/ReshapeOpsUtils.cpp
+++ b/mlir/lib/Dialect/Utils/ReshapeOpsUtils.cpp
@@ -253,7 +253,7 @@
     return true;
   unsigned nDims = reassociation[0].getNumDims();
   unsigned nextExpectedDim = 0;
-  for (auto it : llvm::enumerate(reassociation)) {
+  for (const auto &it : llvm::enumerate(reassociation)) {
     auto m = it.value();
     if (m.getNumDims() != nDims || m.getNumSymbols() != 0) {
       if (invalidIndex)
diff --git a/mlir/lib/Dialect/Vector/VectorMultiDimReductionTransforms.cpp b/mlir/lib/Dialect/Vector/VectorMultiDimReductionTransforms.cpp
--- a/mlir/lib/Dialect/Vector/VectorMultiDimReductionTransforms.cpp
+++ b/mlir/lib/Dialect/Vector/VectorMultiDimReductionTransforms.cpp
@@ -126,7 +126,7 @@
     // 1. Separate reduction and parallel dims.
     SmallVector<int64_t, 4> parallelDims, parallelShapes;
     SmallVector<int64_t, 4> reductionDims, reductionShapes;
-    for (auto it : llvm::enumerate(reductionMask)) {
+    for (const auto &it : llvm::enumerate(reductionMask)) {
       int64_t i = it.index();
       bool isReduction = it.value();
       if (isReduction) {
diff --git a/mlir/lib/Dialect/Vector/VectorOps.cpp b/mlir/lib/Dialect/Vector/VectorOps.cpp
--- a/mlir/lib/Dialect/Vector/VectorOps.cpp
+++ b/mlir/lib/Dialect/Vector/VectorOps.cpp
@@ -269,7 +269,7 @@
   result.addTypes(targetType);
 
   SmallVector<int64_t> reductionDims;
-  for (auto en : llvm::enumerate(reductionMask))
+  for (const auto &en : llvm::enumerate(reductionMask))
     if (en.value())
       reductionDims.push_back(en.index());
   result.addAttribute(getReductionDimsAttrName(),
@@ -613,7 +613,7 @@
   // that the number of map outputs equals the rank of its associated
   // vector operand.
   unsigned numIterators = op.iterator_types().getValue().size();
-  for (auto it : llvm::enumerate(op.indexing_maps())) {
+  for (const auto &it : llvm::enumerate(op.indexing_maps())) {
     auto index = it.index();
     auto map = it.value().cast<AffineMapAttr>().getValue();
     if (map.getNumSymbols() != 0)
@@ -693,7 +693,7 @@
 getDimMap(ArrayRef<AffineMap> indexingMaps, ArrayAttr iteratorTypes,
           StringRef targetIteratorTypeName, MLIRContext *context) {
   std::vector<std::pair<int64_t, int64_t>> dimMap;
-  for (auto it : llvm::enumerate(iteratorTypes)) {
+  for (const auto &it : llvm::enumerate(iteratorTypes)) {
     auto iteratorTypeName = it.value().cast<StringAttr>().getValue();
     if (iteratorTypeName != targetIteratorTypeName)
       continue;
@@ -713,7 +713,7 @@
   auto resVectorType = getResultType().dyn_cast<VectorType>();
   SmallVector<AffineMap, 4> indexingMaps(getIndexingMaps());
   SmallVector<int64_t, 2> iterationShape;
-  for (auto it : llvm::enumerate(iterator_types())) {
+  for (const auto &it : llvm::enumerate(iterator_types())) {
     // Search lhs/rhs map results for 'targetExpr'.
     auto targetExpr = getAffineDimExpr(it.index(), getContext());
     auto iteratorTypeName = it.value().cast<StringAttr>().getValue();
@@ -736,7 +736,7 @@
     std::vector<DenseMap<int64_t, int64_t>> &iterationIndexMap) {
   unsigned numMaps = indexing_maps().getValue().size();
   iterationIndexMap.resize(numMaps);
-  for (auto it : llvm::enumerate(indexing_maps())) {
+  for (const auto &it : llvm::enumerate(indexing_maps())) {
     auto index = it.index();
     auto map = it.value().cast<AffineMapAttr>().getValue();
     for (unsigned i = 0, e = map.getNumResults(); i < e; ++i) {
@@ -932,7 +932,7 @@
   if (positionAttr.size() > static_cast<unsigned>(op.getVectorType().getRank()))
     return op.emitOpError(
         "expected position attribute of rank smaller than vector rank");
-  for (auto en : llvm::enumerate(positionAttr)) {
+  for (const auto &en : llvm::enumerate(positionAttr)) {
     auto attr = en.value().dyn_cast<IntegerAttr>();
     if (!attr || attr.getInt() < 0 ||
         attr.getInt() >= op.getVectorType().getDimSize(en.index()))
@@ -1510,7 +1510,7 @@
     return op.emitOpError("mask length mismatch");
   // Verify all indices.
   int64_t indexSize = v1Type.getDimSize(0) + v2Type.getDimSize(0);
-  for (auto en : llvm::enumerate(maskAttr)) {
+  for (const auto &en : llvm::enumerate(maskAttr)) {
     auto attr = en.value().dyn_cast<IntegerAttr>();
     if (!attr || attr.getInt() < 0 || attr.getInt() >= indexSize)
       return op.emitOpError("mask index #")
@@ -1620,7 +1620,7 @@
       (positionAttr.size() != static_cast<unsigned>(destVectorType.getRank())))
     return op.emitOpError(
         "expected position attribute rank to match the dest vector rank");
-  for (auto en : llvm::enumerate(positionAttr)) {
+  for (const auto &en : llvm::enumerate(positionAttr)) {
     auto attr = en.value().dyn_cast<IntegerAttr>();
     if (!attr || attr.getInt() < 0 ||
         attr.getInt() >= destVectorType.getDimSize(en.index()))
@@ -2794,7 +2794,7 @@
       newIndices.push_back(getValueOrCreateConstantIndexOp(
           rewriter, extractOp.getLoc(), offset));
     }
-    for (auto it : llvm::enumerate(xferOp.indices())) {
+    for (const auto &it : llvm::enumerate(xferOp.indices())) {
       OpFoldResult offset =
           extractOp.getMixedOffsets()[it.index() + rankReduced];
       newIndices.push_back(rewriter.create<arith::AddIOp>(
@@ -3856,7 +3856,7 @@
   if (rank != size)
     return op.emitOpError("transposition length mismatch: ") << size;
   SmallVector<bool, 8> seen(rank, false);
-  for (auto ta : llvm::enumerate(transpAttr)) {
+  for (const auto &ta : llvm::enumerate(transpAttr)) {
     int64_t i = ta.value().cast<IntegerAttr>().getInt();
     if (i < 0 || i >= rank)
       return op.emitOpError("transposition index out of range: ") << i;
@@ -3947,7 +3947,7 @@
   // result dimension size.
   auto resultShape = resultType.getShape();
   SmallVector<int64_t, 4> maskDimSizes;
-  for (auto it : llvm::enumerate(op.mask_dim_sizes())) {
+  for (const auto &it : llvm::enumerate(op.mask_dim_sizes())) {
     int64_t attrValue = it.value().cast<IntegerAttr>().getInt();
     if (attrValue < 0 || attrValue > resultShape[it.index()])
       return op.emitOpError(
diff --git a/mlir/lib/Dialect/Vector/VectorTransferPermutationMapRewritePatterns.cpp b/mlir/lib/Dialect/Vector/VectorTransferPermutationMapRewritePatterns.cpp
--- a/mlir/lib/Dialect/Vector/VectorTransferPermutationMapRewritePatterns.cpp
+++ b/mlir/lib/Dialect/Vector/VectorTransferPermutationMapRewritePatterns.cpp
@@ -79,7 +79,7 @@
     // Apply the reverse transpose to deduce the type of the transfer_read.
     ArrayRef<int64_t> originalShape = op.getVectorType().getShape();
     SmallVector<int64_t> newVectorShape(originalShape.size());
-    for (auto pos : llvm::enumerate(permutation)) {
+    for (const auto &pos : llvm::enumerate(permutation)) {
       newVectorShape[pos.value()] = originalShape[pos.index()];
     }
 
diff --git a/mlir/lib/Dialect/Vector/VectorTransforms.cpp b/mlir/lib/Dialect/Vector/VectorTransforms.cpp
--- a/mlir/lib/Dialect/Vector/VectorTransforms.cpp
+++ b/mlir/lib/Dialect/Vector/VectorTransforms.cpp
@@ -53,7 +53,7 @@
 static SmallVector<Attribute, 4> adjustIter(ArrayAttr iteratorTypes,
                                             int64_t index) {
   SmallVector<Attribute, 4> results;
-  for (auto it : llvm::enumerate(iteratorTypes)) {
+  for (const auto &it : llvm::enumerate(iteratorTypes)) {
     int64_t idx = it.index();
     if (idx == index)
       continue;
@@ -871,7 +871,7 @@
     auto srcMap = rewriter.getMultiDimIdentityMap(reductionMask.size());
     SmallVector<AffineExpr> exprs;
     SmallVector<StringRef> iteratorTypes;
-    for (auto isReduceDim : llvm::enumerate(reductionMask)) {
+    for (const auto &isReduceDim : llvm::enumerate(reductionMask)) {
       if (!isReduceDim.value()) {
         iteratorTypes.push_back(getParallelIteratorTypeName());
         exprs.push_back(rewriter.getAffineDimExpr(isReduceDim.index()));
@@ -997,7 +997,7 @@
           broadcast.getVectorType().getRank() - srcType.getRank();
       bool innerDimBroadcast = false;
       SmallVector<AffineExpr> originalDims;
-      for (auto dim : llvm::enumerate(srcType.getShape())) {
+      for (const auto &dim : llvm::enumerate(srcType.getShape())) {
         if (dim.value() !=
             broadcast.getVectorType().getDimSize(rankDiff + dim.index())) {
           innerDimBroadcast = true;
diff --git a/mlir/lib/Dialect/Vector/VectorUnrollDistribute.cpp b/mlir/lib/Dialect/Vector/VectorUnrollDistribute.cpp
--- a/mlir/lib/Dialect/Vector/VectorUnrollDistribute.cpp
+++ b/mlir/lib/Dialect/Vector/VectorUnrollDistribute.cpp
@@ -52,7 +52,7 @@
       getVectorOffset(originalShape, targetShape, index);
   // Compute 'sliceIndices' by adding 'sliceOffsets[i]' to 'indices[i]'.
   SmallVector<Value> slicedIndices(indices.begin(), indices.end());
-  for (auto dim : llvm::enumerate(permutationMap.getResults())) {
+  for (const auto &dim : llvm::enumerate(permutationMap.getResults())) {
     if (isBroadcast(dim.value()))
       continue;
     unsigned pos = dim.value().cast<AffineDimExpr>().getPosition();
@@ -429,7 +429,7 @@
     for (unsigned i : llvm::seq(unsigned(0), affineMap.getNumResults()))
       map[affineMap.getDimPosition(i)] = extract.getResultType().getDimSize(i);
     SmallVector<Value, 4> extractOperands;
-    for (auto it : llvm::enumerate(contract.getIndexingMaps())) {
+    for (const auto &it : llvm::enumerate(contract.getIndexingMaps())) {
       // For each operands calculate the new vector type after distribution.
       Value operand = contract->getOperand(it.index());
       auto vecType = operand.getType().cast<VectorType>();
diff --git a/mlir/lib/IR/AffineExpr.cpp b/mlir/lib/IR/AffineExpr.cpp
--- a/mlir/lib/IR/AffineExpr.cpp
+++ b/mlir/lib/IR/AffineExpr.cpp
@@ -1020,7 +1020,7 @@
   // as lhs/rhs, and store the indices, constant coefficient corresponding to
   // the indices in `coefficients` map, and affine expression corresponding to
   // in indices in `indexToExprMap` map.
-  for (auto it : llvm::enumerate(localExprs)) {
+  for (const auto &it : llvm::enumerate(localExprs)) {
     AffineExpr expr = it.value();
     if (flatExprs[numDims + numSymbols + it.index()] == 0)
       continue;
diff --git a/mlir/lib/IR/AffineMap.cpp b/mlir/lib/IR/AffineMap.cpp
--- a/mlir/lib/IR/AffineMap.cpp
+++ b/mlir/lib/IR/AffineMap.cpp
@@ -121,7 +121,7 @@
   if (getNumDims() < getNumResults())
     return false;
   unsigned suffixStart = getNumDims() - getNumResults();
-  for (auto idxAndExpr : llvm::enumerate(getResults())) {
+  for (const auto &idxAndExpr : llvm::enumerate(getResults())) {
     unsigned resIdx = idxAndExpr.index();
     AffineExpr expr = idxAndExpr.value();
     if (auto constExpr = expr.dyn_cast<AffineConstantExpr>()) {
@@ -168,7 +168,7 @@
       getNumResults() > getNumInputs() ? getNumResults() - getNumInputs() : 0;
   llvm::SmallBitVector dimFound(std::max(getNumInputs(), getNumResults()),
                                 false);
-  for (auto idxAndExpr : llvm::enumerate(getResults())) {
+  for (const auto &idxAndExpr : llvm::enumerate(getResults())) {
     unsigned resIdx = idxAndExpr.index();
     AffineExpr expr = idxAndExpr.value();
     // Each result may be either a constant 0 (broadcast dimension) or a
@@ -675,7 +675,7 @@
     return map;
   assert(map.getNumSymbols() == 0 && "expected map without symbols");
   SmallVector<AffineExpr, 4> exprs(map.getNumDims());
-  for (auto en : llvm::enumerate(map.getResults())) {
+  for (const auto &en : llvm::enumerate(map.getResults())) {
     auto expr = en.value();
     // Skip non-permutations.
     if (auto d = expr.dyn_cast<AffineDimExpr>()) {
diff --git a/mlir/lib/IR/BuiltinTypes.cpp b/mlir/lib/IR/BuiltinTypes.cpp
--- a/mlir/lib/IR/BuiltinTypes.cpp
+++ b/mlir/lib/IR/BuiltinTypes.cpp
@@ -1036,7 +1036,7 @@
   }
 
   // AffineExpr for strides.
-  for (auto en : llvm::enumerate(strides)) {
+  for (const auto &en : llvm::enumerate(strides)) {
     auto dim = en.index();
     auto stride = en.value();
     assert(stride != 0 && "Invalid stride specification");
diff --git a/mlir/lib/IR/Verifier.cpp b/mlir/lib/IR/Verifier.cpp
--- a/mlir/lib/IR/Verifier.cpp
+++ b/mlir/lib/IR/Verifier.cpp
@@ -316,7 +316,7 @@
       for (Operation &op : block) {
         if (isReachable) {
           // Check that operands properly dominate this use.
-          for (auto operand : llvm::enumerate(op.getOperands())) {
+          for (const auto &operand : llvm::enumerate(op.getOperands())) {
             if (domInfo.properlyDominates(operand.value(), &op))
               continue;
 
diff --git a/mlir/lib/Interfaces/ControlFlowInterfaces.cpp b/mlir/lib/Interfaces/ControlFlowInterfaces.cpp
--- a/mlir/lib/Interfaces/ControlFlowInterfaces.cpp
+++ b/mlir/lib/Interfaces/ControlFlowInterfaces.cpp
@@ -131,7 +131,7 @@
                                  << succInputsTypes.size();
     }
 
-    for (auto typesIdx :
+    for (const auto &typesIdx :
          llvm::enumerate(llvm::zip(*sourceTypes, succInputsTypes))) {
       Type sourceType = std::get<0>(typesIdx.value());
       Type inputType = std::get<1>(typesIdx.value());
@@ -266,7 +266,7 @@
             return false;
           // Compute index of region.
           int64_t beginIndex = -1;
-          for (auto it : llvm::enumerate(branchOp->getRegions()))
+          for (const auto &it : llvm::enumerate(branchOp->getRegions()))
             if (&it.value() == begin)
               beginIndex = it.index();
           assert(beginIndex != -1 && "could not find region in op");
diff --git a/mlir/lib/Interfaces/InferTypeOpInterface.cpp b/mlir/lib/Interfaces/InferTypeOpInterface.cpp
--- a/mlir/lib/Interfaces/InferTypeOpInterface.cpp
+++ b/mlir/lib/Interfaces/InferTypeOpInterface.cpp
@@ -189,7 +189,7 @@
   if (failed(componentTypeFn(context, location, operands, attributes, regions,
                              retComponents)))
     return failure();
-  for (auto shapeAndType : retComponents) {
+  for (const auto &shapeAndType : retComponents) {
     assert(shapeAndType.getAttribute() == nullptr && "attribute not supported");
     if (shapeAndType.hasRank())
       inferredReturnTypes.push_back(RankedTensorType::get(
diff --git a/mlir/lib/Reducer/ReductionTreePass.cpp b/mlir/lib/Reducer/ReductionTreePass.cpp
--- a/mlir/lib/Reducer/ReductionTreePass.cpp
+++ b/mlir/lib/Reducer/ReductionTreePass.cpp
@@ -41,7 +41,7 @@
   std::vector<Operation *> opsNotInRange;
   std::vector<Operation *> opsInRange;
   size_t keepIndex = 0;
-  for (auto op : enumerate(region.getOps())) {
+  for (const auto &op : enumerate(region.getOps())) {
     int index = op.index();
     if (keepIndex < rangeToKeep.size() &&
         index == rangeToKeep[keepIndex].second)
diff --git a/mlir/lib/Rewrite/ByteCode.cpp b/mlir/lib/Rewrite/ByteCode.cpp
--- a/mlir/lib/Rewrite/ByteCode.cpp
+++ b/mlir/lib/Rewrite/ByteCode.cpp
@@ -198,9 +198,9 @@
         maxTypeRangeMemoryIndex(maxTypeRangeMemoryIndex),
         maxValueRangeMemoryIndex(maxValueRangeMemoryIndex),
         maxLoopLevel(maxLoopLevel) {
-    for (auto it : llvm::enumerate(constraintFns))
+    for (const auto &it : llvm::enumerate(constraintFns))
       constraintToMemIndex.try_emplace(it.value().first(), it.index());
-    for (auto it : llvm::enumerate(rewriteFns))
+    for (const auto &it : llvm::enumerate(rewriteFns))
       externalRewriterToMemIndex.try_emplace(it.value().first(), it.index());
   }
 
@@ -631,7 +631,7 @@
     ByteCodeLiveRange &defRange = defIt.second;
 
     // Try to allocate to an existing index.
-    for (auto existingIndexIt : llvm::enumerate(allocatedIndices)) {
+    for (const auto &existingIndexIt : llvm::enumerate(allocatedIndices)) {
       ByteCodeLiveRange &existingRange = existingIndexIt.value();
       if (!defRange.overlaps(existingRange)) {
         existingRange.unionWith(defRange);
diff --git a/mlir/lib/Rewrite/PatternApplicator.cpp b/mlir/lib/Rewrite/PatternApplicator.cpp
--- a/mlir/lib/Rewrite/PatternApplicator.cpp
+++ b/mlir/lib/Rewrite/PatternApplicator.cpp
@@ -53,7 +53,7 @@
   // Apply the cost model to the bytecode patterns first, and then the native
   // patterns.
   if (const PDLByteCode *bytecode = frozenPatternList.getPDLByteCode()) {
-    for (auto it : llvm::enumerate(bytecode->getPatterns()))
+    for (const auto &it : llvm::enumerate(bytecode->getPatterns()))
       mutableByteCodeState->updatePatternBenefit(it.index(), model(it.value()));
   }
 
diff --git a/mlir/lib/Target/LLVMIR/ConvertFromLLVMIR.cpp b/mlir/lib/Target/LLVMIR/ConvertFromLLVMIR.cpp
--- a/mlir/lib/Target/LLVMIR/ConvertFromLLVMIR.cpp
+++ b/mlir/lib/Target/LLVMIR/ConvertFromLLVMIR.cpp
@@ -821,7 +821,7 @@
   currentEntryBlock = blockList[0];
 
   // Add function arguments to the entry block.
-  for (auto kv : llvm::enumerate(f->args()))
+  for (const auto &kv : llvm::enumerate(f->args()))
     instMap[&kv.value()] =
         blockList[0]->addArgument(functionType.getParamType(kv.index()));
 
diff --git a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
--- a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
+++ b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
@@ -380,7 +380,7 @@
     // the case branch that was taken.
     if (switchOp.getDefaultDestination() == current)
       return switchOp.getDefaultOperands()[index];
-    for (auto i : llvm::enumerate(switchOp.getCaseDestinations()))
+    for (const auto &i : llvm::enumerate(switchOp.getCaseDestinations()))
       if (i.value() == current)
         return switchOp.getCaseOperands(i.index())[index];
   }
diff --git a/mlir/lib/Transforms/BufferResultsToOutParams.cpp b/mlir/lib/Transforms/BufferResultsToOutParams.cpp
--- a/mlir/lib/Transforms/BufferResultsToOutParams.cpp
+++ b/mlir/lib/Transforms/BufferResultsToOutParams.cpp
@@ -25,7 +25,7 @@
   // Collect information about the results will become appended arguments.
   SmallVector<Type, 6> erasedResultTypes;
   SmallVector<unsigned, 6> erasedResultIndices;
-  for (auto resultType : llvm::enumerate(functionType.getResults())) {
+  for (const auto &resultType : llvm::enumerate(functionType.getResults())) {
     if (resultType.value().isa<BaseMemRefType>()) {
       erasedResultIndices.push_back(resultType.index());
       erasedResultTypes.push_back(resultType.value());
diff --git a/mlir/lib/Transforms/PipelineDataTransfer.cpp b/mlir/lib/Transforms/PipelineDataTransfer.cpp
--- a/mlir/lib/Transforms/PipelineDataTransfer.cpp
+++ b/mlir/lib/Transforms/PipelineDataTransfer.cpp
@@ -84,7 +84,7 @@
   OpBuilder bOuter(forOp);
   // Put together alloc operands for any dynamic dimensions of the memref.
   SmallVector<Value, 4> allocOperands;
-  for (auto dim : llvm::enumerate(oldMemRefType.getShape())) {
+  for (const auto &dim : llvm::enumerate(oldMemRefType.getShape())) {
     if (dim.value() == ShapedType::kDynamicSize)
       allocOperands.push_back(bOuter.createOrFold<memref::DimOp>(
           forOp.getLoc(), oldMemRef, dim.index()));
diff --git a/mlir/lib/Transforms/Utils/DialectConversion.cpp b/mlir/lib/Transforms/Utils/DialectConversion.cpp
--- a/mlir/lib/Transforms/Utils/DialectConversion.cpp
+++ b/mlir/lib/Transforms/Utils/DialectConversion.cpp
@@ -252,7 +252,7 @@
     op->setLoc(loc);
     op->setAttrs(attrs);
     op->setOperands(operands);
-    for (auto it : llvm::enumerate(successors))
+    for (const auto &it : llvm::enumerate(successors))
       op->setSuccessor(it.value(), it.index());
   }
 
@@ -1255,7 +1255,7 @@
   remapped.reserve(llvm::size(values));
 
   SmallVector<Type, 1> legalTypes;
-  for (auto it : llvm::enumerate(values)) {
+  for (const auto &it : llvm::enumerate(values)) {
     Value operand = it.value();
     Type origType = operand.getType();
 
diff --git a/mlir/lib/Transforms/Utils/InliningUtils.cpp b/mlir/lib/Transforms/Utils/InliningUtils.cpp
--- a/mlir/lib/Transforms/Utils/InliningUtils.cpp
+++ b/mlir/lib/Transforms/Utils/InliningUtils.cpp
@@ -215,7 +215,7 @@
   } else {
     // Otherwise, there were multiple blocks inlined. Add arguments to the post
     // insertion block to represent the results to replace.
-    for (auto resultToRepl : llvm::enumerate(resultsToReplace)) {
+    for (const auto &resultToRepl : llvm::enumerate(resultsToReplace)) {
       resultToRepl.value().replaceAllUsesWith(postInsertBlock->addArgument(
           regionResultTypes[resultToRepl.index()]));
     }
diff --git a/mlir/lib/Transforms/Utils/LoopUtils.cpp b/mlir/lib/Transforms/Utils/LoopUtils.cpp
--- a/mlir/lib/Transforms/Utils/LoopUtils.cpp
+++ b/mlir/lib/Transforms/Utils/LoopUtils.cpp
@@ -3355,7 +3355,7 @@
 
   // Add the body for the full tile loop nest.
   BlockAndValueMapping operandMap;
-  for (auto loopEn : llvm::enumerate(inputNest))
+  for (const auto &loopEn : llvm::enumerate(inputNest))
     operandMap.map(loopEn.value().getInductionVar(),
                    fullTileLoops[loopEn.index()].getInductionVar());
   b = OpBuilder::atBlockTerminator(fullTileLoops.back().getBody());
diff --git a/mlir/lib/Transforms/Utils/RegionUtils.cpp b/mlir/lib/Transforms/Utils/RegionUtils.cpp
--- a/mlir/lib/Transforms/Utils/RegionUtils.cpp
+++ b/mlir/lib/Transforms/Utils/RegionUtils.cpp
@@ -589,7 +589,7 @@
         1 + blocksToMerge.size(),
         SmallVector<Value, 8>(operandsToMerge.size()));
     unsigned curOpIndex = 0;
-    for (auto it : llvm::enumerate(operandsToMerge)) {
+    for (const auto &it : llvm::enumerate(operandsToMerge)) {
       unsigned nextOpOffset = it.value().first - curOpIndex;
       curOpIndex = it.value().first;
 
diff --git a/mlir/test/lib/Dialect/Test/TestPatterns.cpp b/mlir/test/lib/Dialect/Test/TestPatterns.cpp
--- a/mlir/test/lib/Dialect/Test/TestPatterns.cpp
+++ b/mlir/test/lib/Dialect/Test/TestPatterns.cpp
@@ -182,7 +182,7 @@
   if (failed(shapedOp.reifyReturnTypeShapes(b, op->getOperands(), shapes)) ||
       !llvm::hasSingleElement(shapes))
     return;
-  for (auto it : llvm::enumerate(shapes)) {
+  for (const auto &it : llvm::enumerate(shapes)) {
     op->emitRemark() << "value " << it.index() << ": "
                      << it.value().getDefiningOp();
   }
diff --git a/mlir/test/lib/IR/TestPrintDefUse.cpp b/mlir/test/lib/IR/TestPrintDefUse.cpp
--- a/mlir/test/lib/IR/TestPrintDefUse.cpp
+++ b/mlir/test/lib/IR/TestPrintDefUse.cpp
@@ -41,7 +41,7 @@
 
       // Print information about the user of each of the result.
       llvm::outs() << "Has " << op->getNumResults() << " results:\n";
-      for (auto indexedResult : llvm::enumerate(op->getResults())) {
+      for (const auto &indexedResult : llvm::enumerate(op->getResults())) {
         Value result = indexedResult.value();
         llvm::outs() << "  - Result " << indexedResult.index();
         if (result.use_empty()) {
diff --git a/mlir/test/lib/IR/TestSlicing.cpp b/mlir/test/lib/IR/TestSlicing.cpp
--- a/mlir/test/lib/IR/TestSlicing.cpp
+++ b/mlir/test/lib/IR/TestSlicing.cpp
@@ -33,7 +33,7 @@
       builder.create<FuncOp>(loc, clonedFuncOpName, parentFuncOp.getType());
   BlockAndValueMapping mapper;
   builder.setInsertionPointToEnd(clonedFuncOp.addEntryBlock());
-  for (auto arg : enumerate(parentFuncOp.getArguments()))
+  for (const auto &arg : enumerate(parentFuncOp.getArguments()))
     mapper.map(arg.value(), clonedFuncOp.getArgument(arg.index()));
   SetVector<Operation *> slice;
   getBackwardSlice(op, &slice);
diff --git a/mlir/tools/mlir-linalg-ods-gen/mlir-linalg-ods-yaml-gen.cpp b/mlir/tools/mlir-linalg-ods-gen/mlir-linalg-ods-yaml-gen.cpp
--- a/mlir/tools/mlir-linalg-ods-gen/mlir-linalg-ods-yaml-gen.cpp
+++ b/mlir/tools/mlir-linalg-ods-gen/mlir-linalg-ods-yaml-gen.cpp
@@ -361,7 +361,7 @@
 
 static Optional<int>
 findTensorDefArgIndex(StringRef name, SmallVectorImpl<LinalgOperandDef> &args) {
-  for (auto it : llvm::enumerate(args)) {
+  for (const auto &it : llvm::enumerate(args)) {
     if (it.value().name == name)
       return it.index();
   }
@@ -382,7 +382,7 @@
     return std::string("helper.getFloat64Type()");
 
   // Search all argument types.
-  for (auto it : llvm::enumerate(args)) {
+  for (const auto &it : llvm::enumerate(args)) {
     if (it.value().typeVar == typeVar)
       return llvm::formatv("block.getArgument({0}).getType()", it.index())
           .str();
diff --git a/mlir/tools/mlir-tblgen/AttrOrTypeDefGen.cpp b/mlir/tools/mlir-tblgen/AttrOrTypeDefGen.cpp
--- a/mlir/tools/mlir-tblgen/AttrOrTypeDefGen.cpp
+++ b/mlir/tools/mlir-tblgen/AttrOrTypeDefGen.cpp
@@ -561,7 +561,7 @@
       MethodParameter("const KeyTy &", "tblgenKey"));
   if (!def.hasStorageCustomConstructor()) {
     auto &body = construct->body().indent();
-    for (auto it : llvm::enumerate(params)) {
+    for (const auto &it : llvm::enumerate(params)) {
       body << formatv("auto {0} = std::get<{1}>(tblgenKey);\n",
                       it.value().getName(), it.index());
     }
diff --git a/mlir/tools/mlir-tblgen/AttrOrTypeFormatGen.cpp b/mlir/tools/mlir-tblgen/AttrOrTypeFormatGen.cpp
--- a/mlir/tools/mlir-tblgen/AttrOrTypeFormatGen.cpp
+++ b/mlir/tools/mlir-tblgen/AttrOrTypeFormatGen.cpp
@@ -660,7 +660,7 @@
   /// Collect all of the attribute's or type's parameters.
   SmallVector<std::unique_ptr<Element>> vars;
   /// Ensure that none of the parameters have already been captured.
-  for (auto it : llvm::enumerate(def.getParameters())) {
+  for (const auto &it : llvm::enumerate(def.getParameters())) {
     if (seenParams.test(it.index())) {
       return emitError("`params` captures duplicate parameter: " +
                        it.value().getName());
diff --git a/mlir/tools/mlir-tblgen/LLVMIRIntrinsicGen.cpp b/mlir/tools/mlir-tblgen/LLVMIRIntrinsicGen.cpp
--- a/mlir/tools/mlir-tblgen/LLVMIRIntrinsicGen.cpp
+++ b/mlir/tools/mlir-tblgen/LLVMIRIntrinsicGen.cpp
@@ -65,7 +65,7 @@
                                          const char *listName) {
   auto results = record.getValueAsListOfDefs(listName);
   IndicesTy overloadedOps(results.size());
-  for (auto r : llvm::enumerate(results)) {
+  for (const auto &r : llvm::enumerate(results)) {
     llvm::MVT::SimpleValueType vt = getValueType(r.value());
     switch (vt) {
     case llvm::MVT::iAny:
diff --git a/mlir/tools/mlir-tblgen/OpDefinitionsGen.cpp b/mlir/tools/mlir-tblgen/OpDefinitionsGen.cpp
--- a/mlir/tools/mlir-tblgen/OpDefinitionsGen.cpp
+++ b/mlir/tools/mlir-tblgen/OpDefinitionsGen.cpp
@@ -2265,7 +2265,7 @@
 
   body << "  {\n    unsigned index = 0; (void)index;\n";
 
-  for (auto staticValue : llvm::enumerate(values)) {
+  for (const auto &staticValue : llvm::enumerate(values)) {
     const NamedTypeConstraint &value = staticValue.value();
 
     bool hasPredicate = value.hasPredicate();
@@ -2330,7 +2330,7 @@
     return;
 
   body << "  {\n    unsigned index = 0; (void)index;\n";
-  for (auto it : llvm::enumerate(regions)) {
+  for (const auto &it : llvm::enumerate(regions)) {
     const auto &region = it.value();
     if (canSkip(region))
       continue;
diff --git a/mlir/tools/mlir-tblgen/OpDocGen.cpp b/mlir/tools/mlir-tblgen/OpDocGen.cpp
--- a/mlir/tools/mlir-tblgen/OpDocGen.cpp
+++ b/mlir/tools/mlir-tblgen/OpDocGen.cpp
@@ -235,7 +235,7 @@
 
   os << "\nSyntax:\n\n```\n!" << def.getDialect().getName() << "."
      << def.getMnemonic() << "<\n";
-  for (auto it : llvm::enumerate(parameters)) {
+  for (const auto &it : llvm::enumerate(parameters)) {
     const AttrOrTypeParameter &param = it.value();
     os << "  " << param.getSyntax();
     if (it.index() < (parameters.size() - 1))
diff --git a/mlir/tools/mlir-tblgen/OpPythonBindingGen.cpp b/mlir/tools/mlir-tblgen/OpPythonBindingGen.cpp
--- a/mlir/tools/mlir-tblgen/OpPythonBindingGen.cpp
+++ b/mlir/tools/mlir-tblgen/OpPythonBindingGen.cpp
@@ -916,7 +916,7 @@
 
 /// Emits named accessors to regions.
 static void emitRegionAccessors(const Operator &op, raw_ostream &os) {
-  for (auto en : llvm::enumerate(op.getRegions())) {
+  for (const auto &en : llvm::enumerate(op.getRegions())) {
     const NamedRegion &region = en.value();
     if (region.name.empty())
       continue;