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

[via llvm-commits]

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@@ -429,6 +455,48 @@ static bool getLowAndHighPC(const DIE &Die, const DWARFUnit &DU,
   return false;
 }
 
+static void fixupDWARFRanges(DIEBuilder &DIEBlder, DWARFUnit &Unit,
+                             uint64_t Offset) {
+  if (Offset == 0)
+    return;
+
+  const uint16_t Version = Unit.getVersion();
+  if (Version >= 5) {
+    DIE *CUDie = DIEBlder.getUnitDIEbyUnit(Unit);
+    DIEValue RngBaseVal = CUDie->findAttribute(dwarf::DW_AT_rnglists_base);
+    if (RngBaseVal) {
+      uint64_t OldVal = RngBaseVal.getDIEInteger().getValue();
+      DIEBlder.replaceValue(CUDie, dwarf::DW_AT_rnglists_base,
+                            RngBaseVal.getForm(), DIEInteger(OldVal + Offset));
+    }
+  }
+
+  const auto &DIs = DIEBlder.getDIEsByUnit(Unit);
+  for (const auto &DI : DIs) {
+    DIE *Die = DI->Die;
+    DIEValue RangesVal = Die->findAttribute(dwarf::DW_AT_ranges);
+    if (RangesVal &&
+        (Version < 5 || RangesVal.getForm() == dwarf::DW_FORM_sec_offset)) {
+      uint64_t OldVal = RangesVal.getDIEInteger().getValue();
+      // Empty ranges are stored at offset 0 in both local and global
+      // buffers, so must not be shifted during merge.
+      if (OldVal != DebugRangesSectionWriter::getEmptyRangesOffset())
+        DIEBlder.replaceValue(Die, dwarf::DW_AT_ranges, RangesVal.getForm(),
+                              DIEInteger(OldVal + Offset));
+    }
+
+    if (Version < 5) {
----------------
Thrrreeee wrote:

This is not duplicate logic. `fixupDWARFRanges() `adjusts DW_AT_ranges / DW_AT_GNU_ranges_base values by a merge offset when per-bucket local ranges buffers are appended to the global buffer. `finalizeCompileUnits() `performs the deferred final patch for split DWARF: the real global .debug_ranges base is only known after the per-DWO ranges buffer is appended.（earlier code may only record the CU DIE in `updateDWARFObjectAddressRanges()` / `convertToRangesPatchDebugInfo()`  ）

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