[clang] Add fine-grained `__has_feature()` cutout (PR #170822)

[Florian Mayer via cfe-commits]

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@@ -736,6 +743,22 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
   // -f(-no)sanitize=leak should change whether leak detection is enabled by
   // default in ASan?
 
+  // Error if a non-UBSan sanitizer is passed to
+  // `-fsanitize-ignore-for-ubsan-feature=`.
+  //
+  // `shift` is a `SANITIZER_GROUP()`, and so is expanded into its constituents
+  // by `expandSanitizerGroups()` above, though the physical bit is not included
+  // in `SanitizerKind::Undefined`.
+  const SanitizerMask not_ubsan_mask =
+      IgnoreForUbsanFeature &
+      ~(SanitizerKind::Undefined | SanitizerKind::ShiftGroup);
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fmayer wrote:

hmmm. not sure this gymnastics are worth if for the warning

https://github.com/llvm/llvm-project/pull/170822