[llvm] [AArch64] Make compiling arm_neon.h faster (PR #226378)

[Alexis Engelke via llvm-commits]

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@@ -165,10 +166,15 @@ std::optional<AArch64::ExtensionInfo>
 AArch64::parseArchExtension(StringRef ArchExt) {
   if (ArchExt.empty())
     return {};
-  for (const auto &A : Extensions) {
-    if (ArchExt == StrTab[A.UserVisibleName] || ArchExt == StrTab[A.Alias])
-      return A;
-  }
+  static const StringMap<const ExtensionInfo *> NameToExtension = [] {
+    StringMap<const ExtensionInfo *> Map;
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aengelke wrote:

DenseMap<StringRef, X>, strings don't need to be copied/owned.

https://github.com/llvm/llvm-project/pull/226378