[Sema] Avoid repeated hash lookups (NFC) (#112156)

Author: kazutakahirata

clang/lib/Sema/SemaAttr.cpp

@@ -750,12 +750,10 @@ bool Sema::UnifySection(StringRef SectionName, int SectionFlags,
   if (auto A = Decl->getAttr<SectionAttr>())
     if (A->isImplicit())
       PragmaLocation = A->getLocation();
-  auto SectionIt = Context.SectionInfos.find(SectionName);
-  if (SectionIt == Context.SectionInfos.end()) {
-    Context.SectionInfos[SectionName] =
-        ASTContext::SectionInfo(Decl, PragmaLocation, SectionFlags);
+  auto [SectionIt, Inserted] = Context.SectionInfos.try_emplace(
+      SectionName, Decl, PragmaLocation, SectionFlags);
+  if (Inserted)
     return false;
-  }
   // A pre-declared section takes precedence w/o diagnostic.
   const auto &Section = SectionIt->second;
   if (Section.SectionFlags == SectionFlags ||