[BitcodeReader] fix a logic error in vector type element validation

[woodruffw]

Summary

The current code checks whether the vector's element type is a valid structure element type, rather than a valid vector element type. The two have separate implementations and but only accept very slightly different sets of types, which is probably why this wasn't caught before.

[woodruffw]

Increase the context for the patch.

[woodruffw]

Gentle ping for review.

[xgupta]

LGTM, Thanks.

[woodruffw]

Thanks! I don't have commit access so I'll need someone else to do the merge :-)

[xgupta]

just doing after a check-llvm.

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

case bitc::TYPE_CODE_ARRAY:     // ARRAY: [numelts, eltty]
       break;
     case bitc::TYPE_CODE_VECTOR:    // VECTOR: [numelts, eltty] or
                                     //         [numelts, eltty, scalable]
       if (Record.size() < 2)
         return error("Invalid record");
       if (Record[0] == 0)
         return error("Invalid vector length");
       ResultTy = getTypeByID(Record[1]);
-      if (!ResultTy || !StructType::isValidElementType(ResultTy))
+      if (!ResultTy || !VectorType::isValidElementType(ResultTy))
         return error("Invalid type");
       bool Scalable = Record.size() > 2 ? Record[2] : false;
       ResultTy = VectorType::get(ResultTy, Record[0], Scalable);
       break;
     }
 
     if (NumRecords >= TypeList.size())
       return error("Invalid TYPE table");