[llvm] [DTLTO][LLVM] Integrated Distributed ThinLTO (DTLTO) (PR #127749)

[Teresa Johnson via llvm-commits]

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@@ -2142,3 +2182,322 @@ std::vector<int> lto::generateModulesOrdering(ArrayRef<BitcodeModule *> R) {
   });
   return ModulesOrdering;
 }
+
+namespace {
+// For this out-of-process backend no codegen is done when invoked for each
+// task. Instead we generate the required information (e.g. the summary index
+// shard, import list, etc..) to allow for the codegen to be performed
+// externally (similar to WriteIndexesThinBackend). This backend's `wait`
+// function then invokes an external distributor process to do backend
+// compilations.
+class OutOfProcessThinBackend : public CGThinBackend {
+  using SString = SmallString<128>;
+
+  BumpPtrAllocator Alloc;
+  StringSaver Saver{Alloc};
+
+  SString LinkerOutputFile;
+
+  SString DistributorPath;
+  ArrayRef<StringRef> DistributorArgs;
+
+  SString RemoteCompiler;
+  ArrayRef<StringRef> RemoteCompilerArgs;
+
+  bool SaveTemps;
+
+  SmallVector<StringRef, 0> CodegenOptions;
+  DenseSet<StringRef> CommonInputs;
+
+  // Information specific to individual backend compilation job.
+  struct Job {
+    unsigned Task;
+    StringRef ModuleID;
+    StringRef NativeObjectPath;
+    StringRef SummaryIndexPath;
+    ImportsFilesContainer ImportFiles;
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teresajohnson wrote:

Nit: make the spelling consistent, probably "ImportsFiles" everywhere (plural Imports).

https://github.com/llvm/llvm-project/pull/127749