Python: Fix bad join in scope entry transfer

[tausbn]

How it started:

Tuple counts for Base::BaseFlow::scope_entry_value_transfer_from_earlier#f76ef5bb#ffff/4@f2af49f5 after 18s:
1526390  ~0%     {3} r1 = JOIN Base::BaseFlow::scope_entry_value_transfer_from_earlier#f76ef5bb#ffff#shared WITH Essa::EssaVariable::getScope#dispred#f0820431#ff ON FIRST 1 OUTPUT Rhs.1 'pred_scope', Lhs.0 'pred_var', Lhs.1
7798319  ~0%     {4} r2 = JOIN r1 WITH Scope::Scope::precedes#dispred#f0820431#ff ON FIRST 1 OUTPUT Rhs.1 'succ_scope', Lhs.1 'pred_var', Lhs.2, Lhs.0 'pred_scope'

5427334  ~0%     {4} r3 = JOIN Base::BaseFlow::scope_entry_value_transfer_from_earlier#f76ef5bb#ffff#shared#1 WITH Scope::Scope::precedes#dispred#f0820431#ff ON FIRST 1 OUTPUT Lhs.1 'pred_var', Lhs.2, Lhs.0 'pred_scope', Rhs.1 'succ_scope'
5426883  ~0%     {4} r4 = r3 AND NOT Base::BaseFlow::scope_entry_value_transfer_from_earlier#f76ef5bb#ffff#antijoin_rhs(Lhs.0 'pred_var', Lhs.1, Lhs.2 'pred_scope', Lhs.3)
5426883  ~0%     {5} r5 = SCAN r4 OUTPUT In.3, "__init__", In.0 'pred_var', In.1, In.2 'pred_scope'
2002084  ~0%     {4} r6 = JOIN r5 WITH Scope::Scope::getName#dispred#f0820431#fb ON FIRST 2 OUTPUT Lhs.0, Lhs.2 'pred_var', Lhs.3, Lhs.4 'pred_scope'
39293988 ~2%     {4} r7 = JOIN r6 WITH Scope::Scope::precedes#dispred#f0820431#ff ON FIRST 1 OUTPUT Rhs.1 'succ_scope', Lhs.1 'pred_var', Lhs.2, Lhs.3 'pred_scope'

47092307 ~0%     {4} r8 = r2 UNION r7
94173236 ~7%     {5} r9 = JOIN r8 WITH Essa::ScopeEntryDefinition::getScope#dispred#f0820431#ff_10#join_rhs ON FIRST 1 OUTPUT Lhs.2, Rhs.1 'succ_def', Lhs.1 'pred_var', Lhs.3 'pred_scope', Lhs.0 'succ_scope'
599441   ~1%     {4} r10 = JOIN r9 WITH Essa::TEssaNodeDefinition#24e22a14#ffff_03#join_rhs ON FIRST 2 OUTPUT Lhs.2 'pred_var', Lhs.3 'pred_scope', Lhs.1 'succ_def', Lhs.4 'succ_scope'
                return r10

How it ended:

Tuple counts for Base::essa_var_scope#f76ef5bb#fff/3@20fd243c after 153ms:
1526390 ~0%     {2} r1 = JOIN Essa::EssaDefinition::getSourceVariable#dispred#f0820431#ff WITH Base::BaseFlow::reaches_exit#f76ef5bb#f ON FIRST 1 OUTPUT Lhs.0 'pred_var', Lhs.1 'var'
1526390 ~5%     {3} r2 = JOIN r1 WITH Essa::EssaVariable::getScope#dispred#f0820431#ff ON FIRST 1 OUTPUT Lhs.1 'var', Rhs.1 'pred_scope', Lhs.0 'pred_var'
                return r2

Tuple counts for Base::scope_entry_def_scope#f76ef5bb#fff/3@34224fid after 40ms:
581249 ~1%     {3} r1 = JOIN Essa::TEssaNodeDefinition#24e22a14#ffff_30#join_rhs WITH Essa::ScopeEntryDefinition::getScope#dispred#f0820431#ff ON FIRST 1 OUTPUT Lhs.1 'var', Rhs.1 'succ_scope', Lhs.0 'succ_def'
                return r1

Tuple counts for Base::scope_entry_value_transfer_through_init#f76ef5bb#ffff#shared/5@cb3c45lu after 76ms:
471230 ~0%     {3} r1 = JOIN Variables::GlobalVariable#class#3aa06bbf#f WITH Base::scope_entry_def_scope#f76ef5bb#fff ON FIRST 1 OUTPUT Rhs.1 'arg1', Lhs.0 'arg0', Rhs.2 'arg2'
313791 ~2%     {5} r2 = JOIN r1 WITH Base::step_through_init#f76ef5bb#fff ON FIRST 1 OUTPUT Lhs.1 'arg0', Lhs.0 'arg1', Lhs.2 'arg2', Rhs.1 'arg3', Rhs.2 'arg4'
                return r2

Tuple counts for Base::scope_entry_value_transfer_through_init#f76ef5bb#ffff#antijoin_rhs/5@886d8bvr after 67ms:
508926 ~0%      {6} r1 = JOIN Base::scope_entry_value_transfer_through_init#f76ef5bb#ffff#shared WITH Exprs::Name::defines#dispred#f0820431#ff_10#join_rhs ON FIRST 1 OUTPUT Rhs.1, Lhs.4 'arg4', Lhs.0 'arg0', Lhs.1 'arg1', Lhs.2 'arg2', Lhs.3 'arg3'
25     ~46%     {5} r2 = JOIN r1 WITH Exprs::Expr::getScope#dispred#f0820431#ff ON FIRST 2 OUTPUT Lhs.2 'arg0', Lhs.3 'arg1', Lhs.4 'arg2', Lhs.5 'arg3', Lhs.1 'arg4'
                return r2

Tuple counts for Base::scope_entry_value_transfer_through_init#f76ef5bb#ffff/4@87ec703f after 80ms:
313774 ~2%     {5} r1 = Base::scope_entry_value_transfer_through_init#f76ef5bb#ffff#shared AND NOT Base::scope_entry_value_transfer_through_init#f76ef5bb#ffff#antijoin_rhs(Lhs.0, Lhs.1 'succ_scope', Lhs.2 'succ_def', Lhs.3 'pred_scope', Lhs.4)
313774 ~0%     {4} r2 = SCAN r1 OUTPUT In.3 'pred_scope', In.0, In.1 'succ_scope', In.2 'succ_def'
313774 ~4%     {4} r3 = JOIN r2 WITH @py_scope#f ON FIRST 1 OUTPUT Lhs.1, Lhs.0 'pred_scope', Lhs.2 'succ_scope', Lhs.3 'succ_def'
313778 ~0%     {4} r4 = JOIN r3 WITH Base::essa_var_scope#f76ef5bb#fff ON FIRST 2 OUTPUT Rhs.2 'pred_var', Lhs.1 'pred_scope', Lhs.3 'succ_def', Lhs.2 'succ_scope'
                return r4

Tuple counts for Base::step_through_init#f76ef5bb#fff/3@7ba1ee1c after 17ms:
11763  ~0%     {1} r1 = JOIN Scope::Scope::precedes#dispred#f0820431#ff#join_rhs WITH Scope::Scope::getName#dispred#f0820431#fb_10#join_rhs ON FIRST 1 OUTPUT Rhs.1 'init'
196671 ~4%     {2} r2 = JOIN r1 WITH Scope::Scope::precedes#dispred#f0820431#ff ON FIRST 1 OUTPUT Lhs.0 'init', Rhs.1 'succ_scope'
196671 ~6%     {3} r3 = JOIN r2 WITH Scope::Scope::precedes#dispred#f0820431#ff_10#join_rhs ON FIRST 1 OUTPUT Lhs.1 'succ_scope', Rhs.1 'pred_scope', Lhs.0 'init'
                return r3

Tuple counts for Base::BaseFlow::scope_entry_value_transfer_from_earlier#f76ef5bb#ffff/4@4892f93f after 426ms:
1526390 ~0%     {3} r1 = SCAN Base::essa_var_scope#f76ef5bb#fff OUTPUT In.1, In.0, In.2 'pred_var'
7798319 ~0%     {4} r2 = JOIN r1 WITH Scope::Scope::precedes#dispred#f0820431#ff ON FIRST 1 OUTPUT Lhs.1, Rhs.1 'succ_scope', Rhs.0, Lhs.2 'pred_var'
285663  ~3%     {4} r3 = JOIN r2 WITH Base::scope_entry_def_scope#f76ef5bb#fff ON FIRST 2 OUTPUT Lhs.3 'pred_var', Lhs.2 'pred_scope', Rhs.2 'succ_def', Lhs.1 'succ_scope'

599441  ~1%     {4} r4 = Base::scope_entry_value_transfer_through_init#f76ef5bb#ffff UNION r3
                return r4

It's possible this could be improved even further, but I think this is good enough. (I'm not entirely happy with how many helper predicates I ended up needing, but it was the only way I could get the joins to happen in a semi-sensible order.)

[RasmusWL]

a complex rewrite to be sure. Semantically it looks good 👍 From performance point-of-view, I get the gist of it