[llvm] [BOLT][DWARF][NFC] Add parallelization for processing of DWO debug information (PR #100282)

[Sayhaan Siddiqui via llvm-commits]

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@@ -744,9 +754,12 @@ void DWARFRewriter::updateDebugInfo() {
           *DWODIEBuildersByCU.emplace_back(std::move(DWODIEBuilderPtr)).get();
       if (CU->getVersion() >= 5)
         StrOffstsWriter->finalizeSection(*CU, DIEBlder);
-      processSplitCU(*CU, **SplitCU, DIEBlder, *TempRangesSectionWriter,
-                     AddressWriter, DWOName, DwarfOutputPath, DWODIEBuilder);
+      ThreadPool.async([&, DwarfOutputPath, DWOName, CU, SplitCU] {
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sayhaan wrote:

They go out of scope and cause a seg fault.

https://github.com/llvm/llvm-project/pull/100282