[mlir] Remove redundant declarations (NFC) (llvm#166714)

In C++17, static constexpr members are implicitly inline, so they no
longer require an out-of-line definition.

Identified with readability-redundant-declaration.

Author: kazutakahirata

mlir/lib/Dialect/Async/IR/Async.cpp

@@ -17,8 +17,6 @@ using namespace mlir::async;
 
 #include "mlir/Dialect/Async/IR/AsyncOpsDialect.cpp.inc"
 
-constexpr StringRef AsyncDialect::kAllowedToBlockAttrName;
-
 void AsyncDialect::initialize() {
   addOperations<
 #define GET_OP_LIST

mlir/lib/Dialect/DLTI/DLTI.cpp

@@ -606,11 +606,6 @@ FailureOr<Attribute> dlti::query(Operation *op, ArrayRef<StringRef> keys,
   return dlti::query(op, entryKeys, emitError);
 }
 
-constexpr const StringLiteral mlir::DLTIDialect::kDataLayoutAttrName;
-constexpr const StringLiteral mlir::DLTIDialect::kDataLayoutEndiannessKey;
-constexpr const StringLiteral mlir::DLTIDialect::kDataLayoutEndiannessBig;
-constexpr const StringLiteral mlir::DLTIDialect::kDataLayoutEndiannessLittle;
-
 namespace {
 class TargetDataLayoutInterface : public DataLayoutDialectInterface {
 public:

mlir/lib/Dialect/LLVMIR/IR/LLVMDialect.cpp

@@ -640,8 +640,6 @@ SuccessorOperands SwitchOp::getSuccessorOperands(unsigned index) {
 // Code for LLVM::GEPOp.
 //===----------------------------------------------------------------------===//
 
-constexpr int32_t GEPOp::kDynamicIndex;
-
 GEPIndicesAdaptor<ValueRange> GEPOp::getIndices() {
   return GEPIndicesAdaptor<ValueRange>(getRawConstantIndicesAttr(),
                                        getDynamicIndices());

mlir/lib/Dialect/Transform/Interfaces/TransformInterfaces.cpp

@@ -47,8 +47,6 @@ static bool happensBefore(Operation *a, Operation *b) {
 // TransformState
 //===----------------------------------------------------------------------===//
 
-constexpr const Value transform::TransformState::kTopLevelValue;
-
 transform::TransformState::TransformState(
     Region *region, Operation *payloadRoot,
     const RaggedArray<MappedValue> &extraMappings,

mlir/lib/IR/BuiltinTypeInterfaces.cpp

@@ -34,8 +34,6 @@ unsigned FloatType::getFPMantissaWidth() {
 // ShapedType
 //===----------------------------------------------------------------------===//
 
-constexpr int64_t ShapedType::kDynamic;
-
 int64_t ShapedType::getNumElements(ArrayRef<int64_t> shape) {
   int64_t num = 1;
   for (int64_t dim : shape) {

mlir/lib/IR/Operation.cpp

@@ -375,9 +375,6 @@ llvm::hash_code Operation::hashProperties() {
 // Operation Ordering
 //===----------------------------------------------------------------------===//
 
-constexpr unsigned Operation::kInvalidOrderIdx;
-constexpr unsigned Operation::kOrderStride;
-
 /// Given an operation 'other' that is within the same parent block, return
 /// whether the current operation is before 'other' in the operation list
 /// of the parent block.