Dataflow: Another minor join-order fix

[aschackmull]

The first commit tweaks a join-order slightly: We can add the final column of readStepFwd to the join as a noop, but then ap2 = apCons(c, ap1) becomes implied and can be dropped, which simplifies things. This was mainly motivated by the second commit to get a cleaner RA diff.

The second commit fixes an actual join-order issue in S6Graph::localStep/10.
Before:

[2025-01-16 10:31:51] Evaluated non-recursive predicate DataFlowImpl::MakeImpl<Location::Location,DataFlowImplSpecific::JavaDataFlow>::Impl<SensitiveLoggingQuery::SensitiveLoggerFlow::C>::S6Graph::localStep/10#eaf7e0b3@d7e3e562 in 46ms (size: 49487).
Evaluated relational algebra for predicate DataFlowImpl::MakeImpl<Location::Location,DataFlowImplSpecific::JavaDataFlow>::Impl<SensitiveLoggingQuery::SensitiveLoggerFlow::C>::S6Graph::localStep/10#eaf7e0b3@d7e3e562 with tuple counts:
           63139   ~2%    {8} r1 = SCAN `num#DataFlowImpl::MakeImpl<Location::Location,DataFlowImplSpecific::JavaDataFlow>::Impl<SensitiveLoggingQuery::SensitiveLoggerFlow::C>::S6Graph::TPathNodeMid#2a7e4aad` OUTPUT In.0, In.4, In.5, In.6, In.1, In.2, In.3, In.7
            3680   ~0%    {10}    | JOIN WITH `DataFlowImpl::MakeImpl<Location::Location,DataFlowImplSpecific::JavaDataFlow>::Impl<SensitiveLoggingQuery::SensitiveLoggerFlow::C>::Stage6::fwdFlowRead/12#00c1fd2f_0123910115678#join_rhs` ON FIRST 7 OUTPUT Lhs.7, Rhs.7, Lhs.4, Lhs.5, Lhs.6, Rhs.8, Rhs.9, Rhs.10, _, _
            3680   ~0%    {10}    | REWRITE WITH Out.8 := "", Out.9 := false
                      
           63139   ~5%    {8} r2 = SCAN `num#DataFlowImpl::MakeImpl<Location::Location,DataFlowImplSpecific::JavaDataFlow>::Impl<SensitiveLoggingQuery::SensitiveLoggerFlow::C>::S6Graph::TPathNodeMid#2a7e4aad` OUTPUT In.5, In.0, In.1, In.2, In.3, In.4, In.6, In.7
        12371270   ~0%    {10}    | JOIN WITH `DataFlowImpl::MakeImpl<Location::Location,DataFlowImplSpecific::JavaDataFlow>::Impl<SensitiveLoggingQuery::SensitiveLoggerFlow::C>::AccessPath.isCons/2#dispred#830d3217_201#join_rhs` ON FIRST 1 OUTPUT Lhs.1, Lhs.5, Lhs.0, Lhs.6, Rhs.2, Lhs.2, Lhs.3, Lhs.4, Lhs.7, Rhs.1
            1915   ~0%    {10}    | JOIN WITH `DataFlowImpl::MakeImpl<Location::Location,DataFlowImplSpecific::JavaDataFlow>::Impl<SensitiveLoggingQuery::SensitiveLoggerFlow::C>::Stage6::fwdFlowStore/11#24237f6c_012348910567#join_rhs` ON FIRST 8 OUTPUT Lhs.8, Rhs.10, Lhs.5, Lhs.6, Lhs.7, Rhs.8, Lhs.9, Rhs.9, _, _
            1915   ~1%    {10}    | REWRITE WITH Out.8 := "", Out.9 := true
            ...

After:

[2025-01-16 12:10:51] Evaluated non-recursive predicate DataFlowImpl::MakeImpl<Location::Location,DataFlowImplSpecific::JavaDataFlow>::Impl<SensitiveLoggingQuery::SensitiveLoggerFlow::C>::S6Graph::localStep/10#eaf7e0b3@93954fc8 in 6ms (size: 49487).
Evaluated relational algebra for predicate DataFlowImpl::MakeImpl<Location::Location,DataFlowImplSpecific::JavaDataFlow>::Impl<SensitiveLoggingQuery::SensitiveLoggerFlow::C>::S6Graph::localStep/10#eaf7e0b3@93954fc8 with tuple counts:
        63139   ~0%    {8} r1 = SCAN `num#DataFlowImpl::MakeImpl<Location::Location,DataFlowImplSpecific::JavaDataFlow>::Impl<SensitiveLoggingQuery::SensitiveLoggerFlow::C>::S6Graph::TPathNodeMid#2a7e4aad` OUTPUT In.0, In.4, In.5, In.6, In.1, In.2, In.3, In.7
                   
         3680   ~0%    {10} r2 = JOIN r1 WITH `DataFlowImpl::MakeImpl<Location::Location,DataFlowImplSpecific::JavaDataFlow>::Impl<SensitiveLoggingQuery::SensitiveLoggerFlow::C>::Stage6::fwdFlowRead/12#00c1fd2f_0123910115678#join_rhs` ON FIRST 7 OUTPUT Lhs.7, Rhs.7, Lhs.4, Lhs.5, Lhs.6, Rhs.8, Rhs.9, Rhs.10, _, _
         3680   ~0%    {10}    | REWRITE WITH Out.8 := "", Out.9 := false
                   
         1920   ~0%    {9} r3 = JOIN r1 WITH `DataFlowImpl::MakeImpl<Location::Location,DataFlowImplSpecific::JavaDataFlow>::Impl<SensitiveLoggingQuery::SensitiveLoggerFlow::C>::Stage6::fwdFlowStore/11#24237f6c_012389104567#join_rhs` ON FIRST 7 OUTPUT Rhs.7, Lhs.2, Lhs.4, Lhs.5, Lhs.6, Lhs.7, Rhs.8, Rhs.9, Rhs.10
         1915   ~0%    {10}    | JOIN WITH `DataFlowImpl::MakeImpl<Location::Location,DataFlowImplSpecific::JavaDataFlow>::Impl<SensitiveLoggingQuery::SensitiveLoggerFlow::C>::AccessPath.isCons/2#dispred#830d3217_120#join_rhs` ON FIRST 2 OUTPUT Lhs.5, Lhs.8, Lhs.2, Lhs.3, Lhs.4, Lhs.6, Rhs.2, Lhs.7, _, _
         1915   ~0%    {10}    | REWRITE WITH Out.8 := "", Out.9 := true
         ...

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• shared/dataflow/codeql/dataflow/internal/DataFlowImpl.qll: Language not supported

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[hvitved]

Let's maybe do a DCA run for all languages (incl. JS) before merging.

[aschackmull]

Dca is uneventful, merging.