[clang] [TableGen] Avoid repeated hash lookups (NFC) (PR #109372)

[Nikita Popov via cfe-commits]

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@@ -896,9 +896,8 @@ static void OCL2Qual(Sema &S, const OpenCLTypeStruct &Ty,
     if (ImageTypesMap.contains(T->getValueAsString("Name")))
       continue;
     // Check we have not seen this Type
-    if (TypesSeen.contains(T->getValueAsString("Name")))
+    if (!TypesSeen.try_emplace(T->getValueAsString("Name"), true).second)
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nikic wrote:

This is pretty weird, can we make it a StringSet instead? Doesn't look like the value is used.

https://github.com/llvm/llvm-project/pull/109372