[PATCH] D99978: Fixed CodeView GuidAdapter::format to handle GUID bytes in the right order.

[Alexandre Ganea via Phabricator via llvm-commits]

aganea added inline comments.


================
Comment at: llvm/lib/DebugInfo/CodeView/Formatters.cpp:28
   static const char *Lookup = "0123456789ABCDEF";
+  static const uint8_t Order[16] = {3, 2, 1,  0,  5,  4,  7,  6,
+                                    8, 9, 10, 11, 12, 13, 14, 15};
----------------
I know the patch you're proposing is more optimal in terms of runtime performance, but it adds an extra layer of complexity for a reader who was to figure out why memory is read in that way. Since GUIDs are not that used in binary files, performance is maybe less of a concern. We could maybe rewrite the code to be more self-documenting, something along those lines?
```
void GuidAdapter::format(raw_ostream &Stream, StringRef Style) {
  assert(Item.size() == 16 && "Expected 16-byte GUID");
  struct _GUID {
    support::ulittle32_t Data1;
    support::ulittle16_t Data2;
    support::ulittle16_t Data3;
    support::ubig64_t Data4;
  };
  const _GUID *G = reinterpret_cast<const _GUID *>(Item.data());
  Stream << "{"
         << format_hex_no_prefix(G->Data1, sizeof(G->Data1), /*Upper=*/true)
         << '-'
         << format_hex_no_prefix(G->Data2, sizeof(G->Data2), /*Upper=*/true)
         << '-'
         << format_hex_no_prefix(G->Data3, sizeof(G->Data3), /*Upper=*/true)
         << '-'
         << format_hex_no_prefix(G->Data4, sizeof(G->Data4), /*Upper=*/true)
         << "}";
}
```


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D99978/new/

https://reviews.llvm.org/D99978