llvm-project

2274fd8f - [BOLT] Compute local code section names lazily to reduce memory (#214890)

[BOLT] Compute local code section names lazily to reduce memory (#214890) Every BinaryFunction eagerly materialized two std::string members at construction: CodeSectionName (".local.text.<name>") and ColdCodeSectionName (".local.cold.text.<name>"), built by appending the full function name to a fixed prefix. On ELF the name is the (often large, mangled) symbol name, which is already owned by the function's MCSymbol. So every function stored two extra heap copies of its name -- for all functions, whether or not they were ever emitted into a per-function section. During discoverFileObjects on a large binary, this eager construction (buildSectionName -> Twine::str) accounted for 1-2% of RSS (1770MB). Here we make both members std::optional<std::string>, left empty by default, and recompute the default name on demand in getCodeSectionName() from the function's name. Only functions with an explicitly assigned section name (via setCodeSectionName/setColdCodeSectionName -- mostly short constants such as ".text"/".text.cold" set during reordering, plus the injected/patch cases) store a string. The common, unoptimized function stores nothing.