[clang] [Reland][Clang][CodeGen][UBSan] Add more precise attributes to recoverable ubsan handlers (PR #135135)

[Eli Friedman via cfe-commits]

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@@ -3615,6 +3618,23 @@ static void emitCheckHandlerCall(CodeGenFunction &CGF,
         .addAttribute(llvm::Attribute::NoUnwind);
   }
   B.addUWTableAttr(llvm::UWTableKind::Default);
+  // Add more precise attributes to recoverable ubsan handlers for better
+  // optimizations.
+  if (CGF.CGM.getCodeGenOpts().OptimizationLevel > 0 && MayReturn) {
+    // __ubsan_handle_dynamic_type_cache_miss reads the vtable, which is also
+    // accessible by the current module.
+    if (CheckHandler != SanitizerHandler::DynamicTypeCacheMiss) {
+      llvm::MemoryEffects ME =
+          llvm::MemoryEffects::argMemOnly(llvm::ModRefInfo::Ref) |
+          llvm::MemoryEffects::inaccessibleMemOnly();
+      if (MayReadFromPtrToInt)
+        ME |= llvm::MemoryEffects::readOnly();
+      B.addMemoryAttr(ME);
+    }
+    // If the handler does not return, it must interact with the environment in
+    // an observable way.
+    B.addAttribute(llvm::Attribute::MustProgress);
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efriedma-quic wrote:

I know this isn't new... but I don't think this "mustprogress" marking actually does anything useful.  "mustprogress" is more a characteristic of function definitions, not calls.

https://github.com/llvm/llvm-project/pull/135135