[lld] [lld][ELF] Introduce an option to keep data section prefix. (PR #148985)

[Mingming Liu via llvm-commits]

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@@ -105,13 +110,41 @@ StringRef LinkerScript::getOutputSectionName(const InputSectionBase *s) const {
     return ".text";
   }
 
-  for (StringRef v : {".data.rel.ro", ".data",       ".rodata",
-                      ".bss.rel.ro",  ".bss",        ".ldata",
-                      ".lrodata",     ".lbss",       ".gcc_except_table",
-                      ".init_array",  ".fini_array", ".tbss",
-                      ".tdata",       ".ARM.exidx",  ".ARM.extab",
-                      ".ctors",       ".dtors",      ".sbss",
-                      ".sdata",       ".srodata"})
+  // When zKeepDataSectionPrefix is true, keep .hot and .unlikely suffixes
+  // in data sections.
+  static constexpr StringRef dataSectionPrefixes[] = {
+      ".data.rel.ro", ".data", ".rodata", ".bss.rel.ro", ".bss",
+  };
+
+  for (auto [index, v] : llvm::enumerate(dataSectionPrefixes)) {
+    if (isSectionPrefix(v, s->name)) {
+      // The .bss.rel.ro section is considered rarely accessed. So this section
----------------
mingmingl-llvm wrote:

> Make if (isSectionPrefix(v, s->name)) { early return.

Just to confirm, is the early return primarily aimed at optimizing the path where zKeepDataSectionPrefix is false? I'll go ahead and implement it that way.

> .bss.rel.ro is currently only used by LLD's copy relocation feature, not generated by compilers. It's unnecessary to custom stuff with index != 3. Just remove the condition.

Thanks for the information. Removed 'index = 3' stuff, and updated lld/test/ELF/data-section-prefix.s accordingly to have .bss.rel.ro without any prefix.

https://github.com/llvm/llvm-project/pull/148985