[clang] [llvm] Compute GUIDs once and store in metadata (PR #184065)

[Owen Rodley via cfe-commits]

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@@ -7304,9 +7280,13 @@ ModuleSummaryIndexBitcodeReader::getValueInfoFromValueId(unsigned ValueId) {
 void ModuleSummaryIndexBitcodeReader::setValueGUID(
     uint64_t ValueID, StringRef ValueName, GlobalValue::LinkageTypes Linkage,
     StringRef SourceFileName) {
-  std::string GlobalId =
-      GlobalValue::getGlobalIdentifier(ValueName, Linkage, SourceFileName);
-  auto ValueGUID = GlobalValue::getGUIDAssumingExternalLinkage(GlobalId);
+  GlobalValue::GUID ValueGUID = 0;
+  if (ValueID < DefinedGUIDs.size())
+    ValueGUID = DefinedGUIDs[ValueID];
+  if (ValueGUID == 0)
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orodley wrote:

I think it might be possible in theory? The `DefinedGUIDs` list is just initialised to all zeroes and then we set the GUID for every `ValueID`, as long as it has one. So if a particular value doesn't get an assigned `GUID` because it `isDeclaration` then its entry will be 0. I'll try changing this and seeing if this is ever possible in practice.

https://github.com/llvm/llvm-project/pull/184065