[llvm] [NFCI][Globals]For GlobalObjects, add updateSectionPrefix and change setSectionPrefix to handle empty strings (PR #158460)

[Snehasish Kumar via llvm-commits]

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@@ -121,9 +121,14 @@ class GlobalObject : public GlobalValue {
   /// appropriate default object file section.
   LLVM_ABI void setSection(StringRef S);
 
-  /// Set the section prefix for this global object.
+  /// Set the section prefix for this global object. If \p Prefix is empty,
+  /// the section prefix metadata will be cleared if it exists.
   LLVM_ABI void setSectionPrefix(StringRef Prefix);
 
+  /// If \p Prefix is different from existing prefix, update section prefix.
+  /// Returns true if an update happens and false otherwise.
+  LLVM_ABI bool updateSectionPrefix(StringRef Prefix);
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snehasish wrote:

Since updateSectionPrefix calls setSectionPrefix and empty string will drop the metadata here too. I wonder if it's worth noting. 

https://github.com/llvm/llvm-project/pull/158460