[lld] [LLD] Add CLASS syntax to SECTIONS (PR #95323)

[Daniel Thornburgh via llvm-commits]

================
@@ -490,99 +494,131 @@ static void sortInputSections(MutableArrayRef<InputSectionBase *> vec,
 SmallVector<InputSectionBase *, 0>
 LinkerScript::computeInputSections(const InputSectionDescription *cmd,
                                    ArrayRef<InputSectionBase *> sections,
-                                   const OutputSection &outCmd) {
+                                   const SectionBase &outCmd) {
   SmallVector<InputSectionBase *, 0> ret;
-  SmallVector<size_t, 0> indexes;
-  DenseSet<size_t> seen;
   DenseSet<InputSectionBase *> spills;
-  auto sortByPositionThenCommandLine = [&](size_t begin, size_t end) {
-    llvm::sort(MutableArrayRef<size_t>(indexes).slice(begin, end - begin));
-    for (size_t i = begin; i != end; ++i)
-      ret[i] = sections[indexes[i]];
-    sortInputSections(
-        MutableArrayRef<InputSectionBase *>(ret).slice(begin, end - begin),
-        config->sortSection, SortSectionPolicy::None);
+
+  const auto flagsMatch = [cmd](InputSectionBase *sec) {
+    return (sec->flags & cmd->withFlags) == cmd->withFlags &&
+           (sec->flags & cmd->withoutFlags) == 0;
   };
 
   // Collects all sections that satisfy constraints of Cmd.
-  size_t sizeAfterPrevSort = 0;
-  for (const SectionPattern &pat : cmd->sectionPatterns) {
-    size_t sizeBeforeCurrPat = ret.size();
-
-    for (size_t i = 0, e = sections.size(); i != e; ++i) {
-      // Skip if the section is dead or has been matched by a previous pattern
-      // in this input section description.
-      InputSectionBase *sec = sections[i];
-      if (!sec->isLive() || seen.contains(i))
-        continue;
-
-      // For --emit-relocs we have to ignore entries like
-      //   .rela.dyn : { *(.rela.data) }
-      // which are common because they are in the default bfd script.
-      // We do not ignore SHT_REL[A] linker-synthesized sections here because
-      // want to support scripts that do custom layout for them.
-      if (isa<InputSection>(sec) &&
-          cast<InputSection>(sec)->getRelocatedSection())
-        continue;
-
-      // Check the name early to improve performance in the common case.
-      if (!pat.sectionPat.match(sec->name))
-        continue;
-
-      if (!cmd->matchesFile(sec->file) || pat.excludesFile(sec->file) ||
-          (sec->flags & cmd->withFlags) != cmd->withFlags ||
-          (sec->flags & cmd->withoutFlags) != 0)
-        continue;
-
-      if (sec->parent) {
-        // Skip if not allowing multiple matches.
-        if (!config->enableNonContiguousRegions)
+  if (cmd->className.empty()) {
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mysterymath wrote:

Ah, that's a great point. I like `classRef`; the type prevents confusing name vs actual class ptr.

https://github.com/llvm/llvm-project/pull/95323