[lld] [lld] Glob-based BP compression sort groups (PR #185661)

[Zhaoxuan Jiang via llvm-commits]

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@@ -69,6 +73,10 @@ template <class D> struct BPOrderer {
   std::optional<StringRef> static getResolvedLinkageName(StringRef name) {
     return {};
   }
+
+  std::string static getCompressionSubgroupKey(const Section &sec) {
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nocchijiang wrote:

The default `getCompressionSubgroupKey()` is needed for ELF, where we use the shared implementation as-is and do not need backend-specific subgrouping beyond the default single bucket. For Mach-O, this is intended to be overridden soon by the `N_COLD_FUNC` work in #183909, where section-level grouping is not enough because cold and non-cold functions can live in the same section.

If you'd prefer a different shape here, do you have a recommendation?

https://github.com/llvm/llvm-project/pull/185661