[NFC][OpenMP] Move the default declare mapper name suffix to OMPConstants.h (#141964)

This patch moves the default declare mapper name suffix
".omp.default.mapper" to the OMPConstants.h file to be used everywhere
for lowering.

Author: TIFitis

flang/lib/Lower/OpenMP/ClauseProcessor.cpp

@@ -1156,7 +1156,8 @@ void ClauseProcessor::processMapObjects(
         typeSpec = &object.sym()->GetType()->derivedTypeSpec();
 
       if (typeSpec) {
-        mapperIdName = typeSpec->name().ToString() + ".omp.default.mapper";
+        mapperIdName =
+            typeSpec->name().ToString() + llvm::omp::OmpDefaultMapperName;
         if (auto *sym = converter.getCurrentScope().FindSymbol(mapperIdName))
           mapperIdName = converter.mangleName(mapperIdName, sym->owner());
       }

flang/lib/Lower/OpenMP/OpenMP.cpp

@@ -2424,7 +2424,7 @@ genTargetOp(lower::AbstractConverter &converter, lower::SymMap &symTable,
       if (sym.GetType()->category() == semantics::DeclTypeSpec::TypeDerived) {
         auto &typeSpec = sym.GetType()->derivedTypeSpec();
         std::string mapperIdName =
-            typeSpec.name().ToString() + ".omp.default.mapper";
+            typeSpec.name().ToString() + llvm::omp::OmpDefaultMapperName;
         if (auto *sym = converter.getCurrentScope().FindSymbol(mapperIdName))
           mapperIdName = converter.mangleName(mapperIdName, sym->owner());
         if (converter.getModuleOp().lookupSymbol(mapperIdName))

flang/lib/Parser/openmp-parsers.cpp

@@ -1402,7 +1402,7 @@ static OmpMapperSpecifier ConstructOmpMapperSpecifier(
   // This matches the syntax: <type-spec> :: <variable-name>
   if (DerivedTypeSpec * derived{std::get_if<DerivedTypeSpec>(&typeSpec.u)}) {
     return OmpMapperSpecifier{
-        std::get<Name>(derived->t).ToString() + ".omp.default.mapper",
+        std::get<Name>(derived->t).ToString() + llvm::omp::OmpDefaultMapperName,
         std::move(typeSpec), std::move(varName)};
   }
   return OmpMapperSpecifier{std::string("omp.default.mapper"),

llvm/include/llvm/Frontend/OpenMP/OMPConstants.h

@@ -190,6 +190,9 @@ enum class OMPScheduleType {
   LLVM_MARK_AS_BITMASK_ENUM(/* LargestValue */ ModifierMask)
 };
 
+// Default OpenMP mapper name suffix.
+inline constexpr const char *OmpDefaultMapperName = ".omp.default.mapper";
+
 /// Values for bit flags used to specify the mapping type for
 /// offloading.
 enum class OpenMPOffloadMappingFlags : uint64_t {