[llvm] [RFC][BOLT] Add a new parallel DWARF processing(2/2) (PR #197859)

[Jinjie Huang via llvm-commits]

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@@ -535,43 +603,107 @@ static void emitDWOBuilder(const std::string &DWOName,
                          StrOffstsWriter, StrWriter, TempRangesSectionWriter);
 }
 
-using DWARFUnitVec = std::vector<DWARFUnit *>;
-using CUPartitionVector = std::vector<DWARFUnitVec>;
-/// Partitions CUs in to buckets. Bucket size is controlled by
-/// cu-processing-batch-size. All the CUs that have cross CU reference reference
-/// as a source are put in to the same initial bucket.
-static CUPartitionVector partitionCUs(DWARFContext &DwCtx) {
-  CUPartitionVector Vec(2);
-  unsigned Counter = 0;
-  const DWARFDebugAbbrev *Abbr = DwCtx.getDebugAbbrev();
-  for (std::unique_ptr<DWARFUnit> &CU : DwCtx.compile_units()) {
-    Expected<const DWARFAbbreviationDeclarationSet *> AbbrDeclSet =
-        Abbr->getAbbreviationDeclarationSet(CU->getAbbreviationsOffset());
-    if (!AbbrDeclSet) {
-      consumeError(AbbrDeclSet.takeError());
-      return Vec;
-    }
-    bool CrossCURefFound = false;
-    for (const DWARFAbbreviationDeclaration &Decl : *AbbrDeclSet.get()) {
-      for (const DWARFAbbreviationDeclaration::AttributeSpec &Attr :
-           Decl.attributes()) {
-        if (Attr.Form == dwarf::DW_FORM_ref_addr) {
-          CrossCURefFound = true;
+static SmallVector<SmallVector<DWARFUnit *>> partitionCUs(DWARFContext &DwCtx) {
+  SmallVector<DWARFUnit *, 0> AllCUs;
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Jinjie-Huang wrote:

Reserving the size should be better?

https://github.com/llvm/llvm-project/pull/197859