[llvm-dev] LLVM map to specific data model?

Christophe Demez via llvm-dev llvm-dev at lists.llvm.org
Wed Feb 28 08:37:01 PST 2018

I'm currently working on a query engine based on LLVM and looking for 
the "best" approach to map our own generic "data model" within the 

When I do a query, lets say I have athletes and wish to apply a query 
like this :

     age > 18 && result.speed > 15

Here is my data model, it is generic data model and a data schema that 
describe the 'form' of the data. Here are some pseudo-code :

     struct Data
       vector<double> doubleValues;
       vector<double> intValues;
       vector<double> stringValues;

       vector<Data>   children;

     enum class DataPropertyType

     struct DataProperty
       DataPropertyType type;
       string name;
       int index;
       DataSchema* children = nullptr;

     struct DataSchema
       vector<DataProperty> properties;

     // Construct the schema

     DataSchema schPerformance;
     schPerformance.push_back( DataProperty {DPT_DOUBLE, "speed", 0} );

     DataSchema schPerson;
     schPerson.push_back( DataProperty {DPT_INT, "age", 0} );
     schPerson.push_back( DataProperty {DPT_CHILDREN, "result", 1, 
schPerformance}     );

     // Construct one item
     Data performance;
     performance.doubleValues[0] = 20; // speed

     Data person;
     person.intValues[0] = 20; // age
     person.children[0] = performance; // performance

What I wish, is to use the existing 'data schema', predefined before the 
query execution, to allow LLVM to 'map' its JIT directly to my 
structure, it is all about performance.
I wish to avoid dynamic schema lookup and introspection.

The idea is to use the DataSchema and the 'indexes' information + type 
information during code generation.

Then, I have a list of 'Data' I which to filter, lets say :

     // Example of use
     vector<Data> datas;

     ... populate the datas

     vector<Data> result;
     foreach(Data& data : datas)
       if ( query.filter(data) ) result.push_back(data);

Do you know a way, or the best way to apply such strategy ?


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