[NFCI][Globals] In GlobalObjects::setSectionPrefix, do conditional update if existing prefix is not equivalent to the new one. Returns whether prefix changed. (#158460)

Before this change, `setSectionPrefix` overwrites existing section
prefix with new one unconditionally.

After this change, `setSectionPrefix` checks for equivalences, updates
conditionally and returns whether an update happens.

Update the existing callers to make use of the return value. [PR
155337](https://github.com/llvm/llvm-project/pull/155337/files#diff-cc0c67ac89807f4453f0cfea9164944a4650cd6873a468a0f907e7158818eae9)
is a motivating use case whether the 'update' semantic is needed.

1 files changed, 4 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index 9db4c9e..92d8768 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -583,23 +583,23 @@ bool CodeGenPrepare::_run(Function &F) {
   // if requested.
   if (BBSectionsGuidedSectionPrefix && BBSectionsProfileReader &&
       BBSectionsProfileReader->isFunctionHot(F.getName())) {
-    F.setSectionPrefix("hot");
+    EverMadeChange |= F.setSectionPrefix("hot");
   } else if (ProfileGuidedSectionPrefix) {
     // The hot attribute overwrites profile count based hotness while profile
     // counts based hotness overwrite the cold attribute.
     // This is a conservative behabvior.
     if (F.hasFnAttribute(Attribute::Hot) ||
         PSI->isFunctionHotInCallGraph(&F, *BFI))
-      F.setSectionPrefix("hot");
+      EverMadeChange |= F.setSectionPrefix("hot");
     // If PSI shows this function is not hot, we will placed the function
     // into unlikely section if (1) PSI shows this is a cold function, or
     // (2) the function has a attribute of cold.
     else if (PSI->isFunctionColdInCallGraph(&F, *BFI) ||
              F.hasFnAttribute(Attribute::Cold))
-      F.setSectionPrefix("unlikely");
+      EverMadeChange |= F.setSectionPrefix("unlikely");
     else if (ProfileUnknownInSpecialSection && PSI->hasPartialSampleProfile() &&
              PSI->isFunctionHotnessUnknown(F))
-      F.setSectionPrefix("unknown");
+      EverMadeChange |= F.setSectionPrefix("unknown");
   }
 
   /// This optimization identifies DIV instructions that can be