[mlir] generate enum translation functions with unused attribute

[ftynse]

Summary

The functions translating enums to LLVM IR are generated in a single
file included in many places, not all of which use all translations.
Generate functions with "unused" attribute to silence compiler warnings.

mlir/lib/Target/LLVMIR/Dialect/LLVMIR/LLVMToLLVMIRTranslation.cpp

 #include "llvm/IR/MDBuilder.h"
 #include "llvm/IR/MatrixBuilder.h"
 #include "llvm/IR/Operator.h"
 
 using namespace mlir;
 using namespace mlir::LLVM;
 using mlir::LLVM::detail::getLLVMConstant;
 
-// The include below has a static function unused in this translation unit,
-// declare it as such to silence a warning.
-static LLVM_ATTRIBUTE_UNUSED ::llvm::GlobalValue::LinkageTypes
-convertLinkageToLLVM(::mlir::LLVM::Linkage value);
-
 #include "mlir/Dialect/LLVMIR/LLVMConversionEnumsToLLVM.inc"
 
 /// Convert MLIR integer comparison predicate to LLVM IR comparison predicate.
 static llvm::CmpInst::Predicate getLLVMCmpPredicate(ICmpPredicate p) {
   switch (p) {
   case LLVM::ICmpPredicate::eq:
     return llvm::CmpInst::Predicate::ICMP_EQ;
   case LLVM::ICmpPredicate::ne:

mlir/lib/Target/LLVMIR/ModuleTranslation.cpp

 #include "llvm/IR/Verifier.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/Cloning.h"
 
 using namespace mlir;
 using namespace mlir::LLVM;
 using namespace mlir::LLVM::detail;
 
-// The include below has a static function unused in this translation unit,
-// declare it as such to silence a warning.
-static LLVM_ATTRIBUTE_UNUSED ::llvm::InlineAsm::AsmDialect
-convertAsmDialectToLLVM(::mlir::LLVM::AsmDialect value);
-
 #include "mlir/Dialect/LLVMIR/LLVMConversionEnumsToLLVM.inc"
 
 /// Builds a constant of a sequential LLVM type `type`, potentially containing
 /// other sequential types recursively, from the individual constant values
 /// provided in `constants`. `shape` contains the number of elements in nested
 /// sequential types. Reports errors at `loc` and returns nullptr on error.
 static llvm::Constant *
 buildSequentialConstant(ArrayRef<llvm::Constant *> &constants,

mlir/tools/mlir-tblgen/LLVMIRConversionGen.cpp

 static void emitOneEnumToConversion(const llvm::Record *record,
                                     raw_ostream &os) {
   LLVMEnumAttr enumAttr(record);
   StringRef llvmClass = enumAttr.getLLVMClassName();
   StringRef cppClassName = enumAttr.getEnumClassName();
   StringRef cppNamespace = enumAttr.getCppNamespace();
 
   // Emit the function converting the enum attribute to its LLVM counterpart.
-  os << formatv("static {0} convert{1}ToLLVM({2}::{1} value) {{\n", llvmClass,
-                cppClassName, cppNamespace);
+  os << formatv(
+      "static LLVM_ATTRIBUTE_UNUSED {0} convert{1}ToLLVM({2}::{1} value) {{\n",
+      llvmClass, cppClassName, cppNamespace);
   os << "  switch (value) {\n";
 
   for (const auto &enumerant : enumAttr.getAllCases()) {
     StringRef llvmEnumerant = enumerant.getLLVMEnumerant();
     StringRef cppEnumerant = enumerant.getSymbol();
     os << formatv("  case {0}::{1}::{2}:\n", cppNamespace, cppClassName,
                   cppEnumerant);
     os << formatv("    return {0}::{1};\n", llvmClass, llvmEnumerant);

 static void emitOneEnumFromConversion(const llvm::Record *record,
                                       raw_ostream &os) {
   LLVMEnumAttr enumAttr(record);
   StringRef llvmClass = enumAttr.getLLVMClassName();
   StringRef cppClassName = enumAttr.getEnumClassName();
   StringRef cppNamespace = enumAttr.getCppNamespace();
 
   // Emit the function converting the enum attribute from its LLVM counterpart.
-  os << formatv("inline {0}::{1} convert{1}FromLLVM({2} value) {{\n",
+  os << formatv("inline LLVM_ATTRIBUTE_UNUSED {0}::{1} convert{1}FromLLVM({2} "
+                "value) {{\n",
                 cppNamespace, cppClassName, llvmClass);
   os << "  switch (value) {\n";
 
   for (const auto &enumerant : enumAttr.getAllCases()) {
     StringRef llvmEnumerant = enumerant.getLLVMEnumerant();
     StringRef cppEnumerant = enumerant.getSymbol();
     os << formatv("  case {0}::{1}:\n", llvmClass, llvmEnumerant);
     os << formatv("    return {0}::{1}::{2};\n", cppNamespace, cppClassName,