[llvm] [IR]Support set/read/update the section prefix for global objects (PR #125757)

[Snehasish Kumar via llvm-commits]

================
@@ -286,6 +287,35 @@ void GlobalObject::setSection(StringRef S) {
   setGlobalObjectFlag(HasSectionHashEntryBit, !S.empty());
 }
 
+void GlobalObject::setSectionPrefix(StringRef Prefix) {
+  MDBuilder MDB(getContext());
+  setMetadata(LLVMContext::MD_section_prefix,
+              MDB.createGlobalObjectSectionPrefix(Prefix));
+}
+
+void GlobalObject::updateSectionPrefix(StringRef Prefix,
----------------
snehasish wrote:

In the cases that I could find in #125756 we could use something like `if (! getSectionPrefix == "hot") setSectionPrefix("unlikely");` instead of this helper. Do we really need a helper for this?

https://github.com/llvm/llvm-project/pull/125757