C++: Project away why to prevent tuple duplication in Buffer.qll

[MathiasVP]

Iteration 3 performed really poorly on basically all forks of https://github.com/OISF/suricata:

Tuple counts for Buffer#61e3d199::getBufferSize#2#fff/3@i3#ffc522h5 after 7m31s:
  13721000    ~3205%       {2} r1 = SCAN Buffer#61e3d199::getBufferSize#2#fff#prev_delta OUTPUT In.0, In.1 'why'
  1315097     ~403%        {2} r2 = JOIN r1 WITH DataFlowUtil#47741e1f::ExprFlowCached::localExprFlowStep#2#ff ON FIRST 1 OUTPUT Rhs.1 'bufferExpr', Lhs.1 'why'
  40865305    ~365%        {3} r3 = JOIN r2 WITH __Buffer#61e3d199::getBufferSize#2#fff#prev_Buffer#61e3d199::getBufferSize#2#fff#prev_delta_DataFlow__#join_rhs ON FIRST 1 OUTPUT Lhs.0 'bufferExpr', Lhs.1 'why', Rhs.1 'result'
  
  7479500     ~662397%     {1} r4 = SCAN Buffer#61e3d199::getBufferSize#2#fff#prev_delta OUTPUT In.0
  53000       ~5094%       {1} r5 = JOIN r4 WITH DataFlowUtil#47741e1f::ExprFlowCached::localExprFlowStep#2#ff ON FIRST 1 OUTPUT Rhs.1 'bufferExpr'
  70000       ~550%        {2} r6 = JOIN r5 WITH __Buffer#61e3d199::getBufferSize#2#fff#prev_Buffer#61e3d199::getBufferSize#2#fff#prev_delta_DataFlow__#join_rhs ON FIRST 1 OUTPUT Lhs.0 'bufferExpr', Rhs.1 'result'
  802603      ~1166%       {3} r7 = JOIN r6 WITH DataFlowUtil#47741e1f::ExprFlowCached::localExprFlowStep#2#ff_10#join_rhs ON FIRST 1 OUTPUT Rhs.1, Lhs.0 'bufferExpr', Lhs.1 'result'
  13769627773 ~226508%     {3} r8 = JOIN r7 WITH Buffer#61e3d199::getBufferSize#2#fff#prev ON FIRST 1 OUTPUT Lhs.1 'bufferExpr', Rhs.1 'why', Lhs.2 'result'
  
  13810493078 ~156967%     {3} r9 = r3 UNION r8
  
  0           ~0%          {3} r10 = SCAN Buffer#61e3d199::getBufferSize#2#fff#prev_delta OUTPUT _, In.0, In.2
  0           ~0%          {3} r11 = REWRITE r10 WITH Out.0 := -1
  0           ~0%          {3} r12 = JOIN r11 WITH Expr#ef463c5d::Expr::getChild#1#dispred#fff_120#join_rhs ON FIRST 2 OUTPUT Rhs.2 'bufferExpr', Lhs.1, Lhs.2
  0           ~0%          {3} r13 = JOIN r12 WITH Access#8878f617::VariableAccess#f ON FIRST 1 OUTPUT Lhs.0 'bufferExpr', Lhs.1, Lhs.2
  0           ~0%          {4} r14 = JOIN r13 WITH Access#8878f617::Access::getTarget#0#dispred#ff ON FIRST 1 OUTPUT Rhs.1 'why', Lhs.1, Lhs.2, Lhs.0 'bufferExpr'
  0           ~0%          {5} r15 = JOIN r14 WITH Buffer#61e3d199::memberMayBeVarSize#2#ff_10#join_rhs ON FIRST 1 OUTPUT Lhs.1, Lhs.2, Lhs.3 'bufferExpr', Lhs.0 'why', Rhs.1
  0           ~0%          {5} r16 = JOIN r15 WITH Access#8878f617::Access::getTarget#0#dispred#ff ON FIRST 1 OUTPUT Lhs.4, Lhs.1, Lhs.2 'bufferExpr', Lhs.3 'why', Rhs.1 'why'
  0           ~0%          {6} r17 = JOIN r16 WITH Type#2e8eb3ef::DerivedType::getBaseType#0#dispred#ff_10#join_rhs ON FIRST 1 OUTPUT Rhs.1, Lhs.1, Lhs.2 'bufferExpr', Lhs.3 'why', Lhs.0, Lhs.4
  0           ~0%          {6} r18 = JOIN r17 WITH Type#2e8eb3ef::PointerType#f ON FIRST 1 OUTPUT Lhs.5, Lhs.0, Lhs.1, Lhs.2 'bufferExpr', Lhs.3 'why', Lhs.4
  0           ~0%          {4} r19 = JOIN r18 WITH Variable#7a968d4e::Variable::getUnspecifiedType#0#dispred#ff ON FIRST 2 OUTPUT Lhs.5, Lhs.2, Lhs.3 'bufferExpr', Lhs.4 'why'
  
  0           ~0%          {5} r20 = JOIN r19 WITH Type#2e8eb3ef::Type::getSize#0#dispred#ff ON FIRST 1 OUTPUT Lhs.1, Lhs.2 'bufferExpr', Lhs.3 'why', Rhs.1, _
  0           ~0%          {5} r21 = REWRITE r20 WITH Tmp.4 := 0, Out.4 := (InOut.0 + Tmp.4)
                            {5} r22 = r21 AND NOT _Access#8878f617::Access::getTarget#0#dispred#ff_Access#8878f617::VariableAccess#f_Buffer#61e3d199::__#antijoin_rhs(Lhs.0, Lhs.1 'bufferExpr', Lhs.2 'why', Lhs.3)
  0           ~0%          {5} r23 = SCAN r22 OUTPUT In.1 'bufferExpr', In.2 'why', _, In.4, In.3
  0           ~0%          {3} r24 = REWRITE r23 WITH Out.2 'result' := (In.3 - In.4) KEEPING 3
  
  0           ~0%          {4} r25 = JOIN r19 WITH Type#2e8eb3ef::Type::getSize#0#dispred#ff ON FIRST 1 OUTPUT Lhs.3 'why', Lhs.1, Lhs.2 'bufferExpr', Rhs.1
  0           ~0%          {5} r26 = JOIN r25 WITH Variable#7a968d4e::Variable::getType#0#dispred#ff ON FIRST 1 OUTPUT Lhs.0 'why', Lhs.1, Lhs.2 'bufferExpr', Lhs.3, Rhs.1
  0           ~0%          {6} r27 = JOIN r26 WITH Variable#7a968d4e::Variable::getType#0#dispred#ff ON FIRST 1 OUTPUT Rhs.1, Lhs.1, Lhs.2 'bufferExpr', Lhs.0 'why', Lhs.3, Lhs.4
  0           ~0%          {5} r28 = JOIN r27 WITH project#Type#2e8eb3ef::Type::getSize#0#dispred#ff ON FIRST 1 OUTPUT Lhs.5, Lhs.1, Lhs.2 'bufferExpr', Lhs.3 'why', Lhs.4
  0           ~0%          {6} r29 = JOIN r28 WITH Type#2e8eb3ef::Type::getSize#0#dispred#ff ON FIRST 1 OUTPUT Lhs.2 'bufferExpr', Lhs.3 'why', _, Lhs.1, Rhs.1, Lhs.4
  0           ~0%          {3} r30 = REWRITE r29 WITH Tmp.2 := (In.3 + In.4), Out.2 'result' := (Tmp.2 - In.5) KEEPING 3
  
  0           ~0%          {3} r31 = r24 UNION r30
  13810493078 ~156967%     {3} r32 = r9 UNION r31
  0           ~0%          {3} r33 = r32 AND NOT Buffer#61e3d199::getBufferSize#2#fff#prev(Lhs.0 'bufferExpr', Lhs.1 'why', Lhs.2 'result')
                            return r33

(I cancelled the pipeline midway.)

After this change we can fully evaluate predicate and we get:

Pipeline standard for Buffer#61e3d199::getBufferSize#2#fff@5441bw59 was evaluated in 87 iterations totaling 10027ms (delta sizes total: 12964791).
    14403190  ~2720%    {2} r1 = SCAN Buffer#61e3d199::getBufferSize#2#fff#prev_delta OUTPUT In.0, In.1
    2806382   ~322%    {2} r2 = JOIN r1 WITH DataFlowUtil#47741e1f::ExprFlowCached::localExprFlowStep#2#ff ON FIRST 1 OUTPUT Rhs.1, Lhs.1
    39977376   ~355%    {3} r3 = JOIN r2 WITH __Buffer#61e3d199::getBufferSize#2#fff#prev_delta_Buffer#61e3d199::getBufferSizeProj#1#ff#prev_DataF__#join_rhs ON FIRST 1 OUTPUT Lhs.0, Lhs.1, Rhs.1
                    
      101888   ~332%    {1} r4 = SCAN Buffer#61e3d199::getBufferSizeProj#1#ff#prev_delta OUTPUT In.0
      15895    ~76%    {1} r5 = JOIN r4 WITH DataFlowUtil#47741e1f::ExprFlowCached::localExprFlowStep#2#ff ON FIRST 1 OUTPUT Rhs.1
      34730    ~22%    {2} r6 = JOIN r5 WITH __Buffer#61e3d199::getBufferSizeProj#1#ff#prev_Buffer#61e3d199::getBufferSizeProj#1#ff#prev_delta_Da__#join_rhs ON FIRST 1 OUTPUT Lhs.0, Rhs.1
      157715    ~64%    {3} r7 = JOIN r6 WITH DataFlowUtil#47741e1f::ExprFlowCached::localExprFlowStep#2#ff_10#join_rhs ON FIRST 1 OUTPUT Rhs.1, Lhs.0, Lhs.1
    81632413   ~496%    {3} r8 = JOIN r7 WITH Buffer#61e3d199::getBufferSize#2#fff#prev ON FIRST 1 OUTPUT Lhs.1, Rhs.1, Lhs.2
                    
  121609789   ~450%    {3} r9 = r3 UNION r8
                    
      101888     ~1%    {3} r10 = SCAN Buffer#61e3d199::getBufferSizeProj#1#ff#prev_delta OUTPUT _, In.0, In.1
      101888     ~0%    {3} r11 = REWRITE r10 WITH Out.0 := -1
        1483     ~0%    {3} r12 = JOIN r11 WITH Expr#ef463c5d::Expr::getChild#1#dispred#fff_120#join_rhs ON FIRST 2 OUTPUT Rhs.2, Lhs.1, Lhs.2
        1483     ~0%    {3} r13 = JOIN r12 WITH Access#8878f617::VariableAccess#f ON FIRST 1 OUTPUT Lhs.0, Lhs.1, Lhs.2
        1483     ~0%    {4} r14 = JOIN r13 WITH Access#8878f617::Access::getTarget#0#dispred#ff ON FIRST 1 OUTPUT Rhs.1, Lhs.1, Lhs.2, Lhs.0
          0     ~0%    {5} r15 = JOIN r14 WITH Buffer#61e3d199::memberMayBeVarSize#2#ff_10#join_rhs ON FIRST 1 OUTPUT Lhs.1, Lhs.2, Lhs.3, Lhs.0, Rhs.1
          0     ~0%    {5} r16 = JOIN r15 WITH Access#8878f617::Access::getTarget#0#dispred#ff ON FIRST 1 OUTPUT Lhs.4, Lhs.1, Lhs.2, Lhs.3, Rhs.1
          0     ~0%    {6} r17 = JOIN r16 WITH Type#2e8eb3ef::DerivedType::getBaseType#0#dispred#ff_10#join_rhs ON FIRST 1 OUTPUT Rhs.1, Lhs.1, Lhs.2, Lhs.3, Lhs.0, Lhs.4
          0     ~0%    {6} r18 = JOIN r17 WITH Type#2e8eb3ef::PointerType#f ON FIRST 1 OUTPUT Lhs.5, Lhs.0, Lhs.1, Lhs.2, Lhs.3, Lhs.4
          0     ~0%    {4} r19 = JOIN r18 WITH Variable#7a968d4e::Variable::getUnspecifiedType#0#dispred#ff ON FIRST 2 OUTPUT Lhs.5, Lhs.2, Lhs.3, Lhs.4
                    
          0     ~0%    {5} r20 = JOIN r19 WITH Type#2e8eb3ef::Type::getSize#0#dispred#ff ON FIRST 1 OUTPUT Lhs.1, Lhs.2, Lhs.3, Rhs.1, _
          0     ~0%    {5} r21 = REWRITE r20 WITH Tmp.4 := 0, Out.4 := (InOut.0 + Tmp.4)
                        {5} r22 = r21 AND NOT _Access#8878f617::Access::getTarget#0#dispred#ff_Access#8878f617::VariableAccess#f_Buffer#61e3d199::__#antijoin_rhs(Lhs.0, Lhs.1, Lhs.2, Lhs.3)
          0     ~0%    {5} r23 = SCAN r22 OUTPUT In.1, In.2, _, In.4, In.3
          0     ~0%    {3} r24 = REWRITE r23 WITH Out.2 := (In.3 - In.4) KEEPING 3
                    
          0     ~0%    {4} r25 = JOIN r19 WITH Type#2e8eb3ef::Type::getSize#0#dispred#ff ON FIRST 1 OUTPUT Lhs.3, Lhs.1, Lhs.2, Rhs.1
          0     ~0%    {5} r26 = JOIN r25 WITH Variable#7a968d4e::Variable::getType#0#dispred#ff ON FIRST 1 OUTPUT Lhs.0, Lhs.1, Lhs.2, Lhs.3, Rhs.1
          0     ~0%    {6} r27 = JOIN r26 WITH Variable#7a968d4e::Variable::getType#0#dispred#ff ON FIRST 1 OUTPUT Rhs.1, Lhs.1, Lhs.2, Lhs.0, Lhs.3, Lhs.4
          0     ~0%    {5} r28 = JOIN r27 WITH project#Type#2e8eb3ef::Type::getSize#0#dispred#ff ON FIRST 1 OUTPUT Lhs.5, Lhs.1, Lhs.2, Lhs.3, Lhs.4
          0     ~0%    {6} r29 = JOIN r28 WITH Type#2e8eb3ef::Type::getSize#0#dispred#ff ON FIRST 1 OUTPUT Lhs.2, Lhs.3, _, Lhs.1, Rhs.1, Lhs.4
          0     ~0%    {3} r30 = REWRITE r29 WITH Tmp.2 := (In.3 + In.4), Out.2 := (Tmp.2 - In.5) KEEPING 3
                    
          0     ~0%    {3} r31 = r24 UNION r30
  121609789   ~450%    {3} r32 = r9 UNION r31
    79073251   ~507%    {3} r33 = r32 AND NOT Buffer#61e3d199::getBufferSize#2#fff#prev(Lhs.0, Lhs.1, Lhs.2)
                        return r33

[MathiasVP]

DCA looks good. So this should be perfectly safe to merge as a fix if QA comes back unhappy