[CLANG] Fix potential integer overflow value in getRVVTypeSize()

[Manna]

Summary

In getRVVTypeSize(clang::​ASTContext &, clang::​BuiltinType const *) potential integer overflow occurs on expression VScale->first * MinElts with type unsigned int (32 bits, unsigned) is evaluated using 32-bit arithmetic, and then used in a context that expects an expression of type uint64_t (64 bits, unsigned).

To avoid integer overflow, this patch changes the types of variables MinElts and EltSize to uint64_t instead of the cast.

[erichkeane]

clang/lib/AST/ASTContext.cpp

9567

I think I'd suggest just changing the types of these two variables instead of the cast.

[Manna]

Thank you @erichkeane for review and comments. I have changed the types of variables MinElts and EltSize to uint64_t instead of the cast.

clang/lib/AST/ASTContext.cpp

 static uint64_t getRVVTypeSize(ASTContext &Context, const BuiltinType *Ty) {
   assert(Ty->isRVVVLSBuiltinType() && "Invalid RVV Type");
   auto VScale = Context.getTargetInfo().getVScaleRange(Context.getLangOpts());
   if (!VScale)
     return 0;
 
   ASTContext::BuiltinVectorTypeInfo Info = Context.getBuiltinVectorTypeInfo(Ty);
 
   unsigned EltSize = Context.getTypeSize(Info.ElementType);
   unsigned MinElts = Info.EC.getKnownMinValue();
-  return VScale->first * MinElts * EltSize;
+  return VScale->first * static_cast<uint64_t>(MinElts) * EltSize;
 }
 
 bool ASTContext::areCompatibleRVVTypes(QualType FirstType,
                                        QualType SecondType) {
   assert(
       ((FirstType->isRVVSizelessBuiltinType() && SecondType->isVectorType()) ||
        (FirstType->isVectorType() && SecondType->isRVVSizelessBuiltinType())) &&
       "Expected RVV builtin type and vector type!");