[llvm] [DWARF] Speedup .gdb_index dumping (PR #151806)

[David Blaikie via llvm-commits]

================
@@ -60,6 +61,24 @@ void DWARFGdbIndex::dumpSymbolTable(raw_ostream &OS) const {
                ", filled slots:",
                SymbolTableOffset, (uint64_t)SymbolTable.size())
      << '\n';
+
+  std::unordered_map<uint32_t, decltype(ConstantPoolVectors)::const_iterator>
+      CuVectorMap{};
+  CuVectorMap.reserve(ConstantPoolVectors.size());
+  const auto FindCuVector =
+      [&CuVectorMap, notFound = ConstantPoolVectors.end()](uint32_t vecOffset) {
+        const auto it = CuVectorMap.find(vecOffset);
+        if (it != CuVectorMap.end()) {
+          return it->second;
+        }
----------------
dwblaikie wrote:

LLVM's coding style skips `{}` on single-line blocks, and reduces scope where possible, so probably something like:
```
if (auto it = CuVectorMap.find(vecOffset); it != CuVectorMap.end())
  return it->second;
```

https://github.com/llvm/llvm-project/pull/151806