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Comment:Remove an unnecessary stack variable from sqlite3VdbeExec().
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SHA1:c54bd9c82dd34951dc87848c0b19fcccaef928db
User & Date: drh 2016-08-13 14:17:02
Context
2016-08-18
15:15
Simplify the vector comparison code generator logic, and the resulting VDBE code. check-in: e2ad0b5d user: drh tags: rowvalue
2016-08-13
14:17
Remove an unnecessary stack variable from sqlite3VdbeExec(). Closed-Leaf check-in: c54bd9c8 user: drh tags: vector-compare
13:03
Improvements to commits. No code changes. check-in: 18f5a3be user: drh tags: vector-compare
Changes
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Changes to src/vdbe.c.

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#ifdef SQLITE_DEBUG
  int nExtraDelete = 0;      /* Verifies FORDELETE and AUXDELETE flags */
#endif
  int rc = SQLITE_OK;        /* Value to return */
  sqlite3 *db = p->db;       /* The database */
  u8 resetSchemaOnFault = 0; /* Reset schema after an error if positive */
  u8 encoding = ENC(db);     /* The database encoding */
  int iCompare = 0;          /* Result of last OP_Compare operation */
  unsigned nVmStep = 0;      /* Number of virtual machine steps */
#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
  unsigned nProgressLimit = 0;/* Invoke xProgress() when nVmStep reaches this */
#endif
  Mem *aMem = p->aMem;       /* Copy of p->aMem */
  Mem *pIn1 = 0;             /* 1st input operand */
  Mem *pIn2 = 0;             /* 2nd input operand */
  Mem *pIn3 = 0;             /* 3rd input operand */
  Mem *pOut = 0;             /* Output operand */
  int *aPermute = 0;         /* Permutation of columns for OP_Compare */
  i64 lastRowid = db->lastRowid;  /* Saved value of the last insert ROWID */
  int cmpRes;                /* Result of last comparison operation */
#ifdef VDBE_PROFILE
  u64 start;                 /* CPU clock count at start of opcode */
#endif
  /*** INSERT STACK UNION HERE ***/

  assert( p->magic==VDBE_MAGIC_RUN );  /* sqlite3_step() verifies this */
  sqlite3VdbeEnter(p);
................................................................................
      assert( pOp->opcode==OP_Eq || pOp->opcode==OP_Ne );
      assert( (flags1 & MEM_Cleared)==0 );
      assert( (pOp->p5 & SQLITE_JUMPIFNULL)==0 );
      if( (flags1&MEM_Null)!=0
       && (flags3&MEM_Null)!=0
       && (flags3&MEM_Cleared)==0
      ){
        cmpRes = 0;  /* Operands are equal */
      }else{
        cmpRes = 1;  /* Operands are not equal */
      }
    }else{
      /* SQLITE_NULLEQ is clear and at least one operand is NULL,
      ** then the result is always NULL.
      ** The jump is taken if the SQLITE_JUMPIFNULL bit is set.
      */
      cmpRes = 1;    /* Operands are not equal */
      if( pOp->p5 & SQLITE_STOREP2 ){
        pOut = &aMem[pOp->p2];
        memAboutToChange(p, pOut);
        MemSetTypeFlag(pOut, MEM_Null);
        REGISTER_TRACE(pOp->p2, pOut);
      }else{
        VdbeBranchTaken(2,3);
................................................................................
      sqlite3VdbeMemExpandBlob(pIn1);
      flags1 &= ~MEM_Zero;
    }
    if( flags3 & MEM_Zero ){
      sqlite3VdbeMemExpandBlob(pIn3);
      flags3 &= ~MEM_Zero;
    }
    cmpRes = sqlite3MemCompare(pIn3, pIn1, pOp->p4.pColl);
  }
  switch( pOp->opcode ){
    case OP_Eq:    res = cmpRes==0;     break;
    case OP_Ne:    res = cmpRes!=0;     break;
    case OP_Lt:    res = cmpRes<0;      break;
    case OP_Le:    res = cmpRes<=0;     break;
    case OP_Gt:    res = cmpRes>0;      break;
    case OP_Ge:    res = cmpRes>=0;     break;
  }

  /* Undo any changes made by applyAffinity() to the input registers. */
  assert( (pIn1->flags & MEM_Dyn) == (flags1 & MEM_Dyn) );
  pIn1->flags = flags1;
  assert( (pIn3->flags & MEM_Dyn) == (flags3 & MEM_Dyn) );
  pIn3->flags = flags3;
................................................................................
** operator and if the result of that Eq would be NULL or false (0), then
** then jump to P2.  If the result of comparing the two previous operands
** using Eq would have been true (1), then fall through.
*/
case OP_ElseNotEq: {       /* same as TK_ESCAPE, jump */
  assert( pOp>aOp );
  assert( pOp[-1].opcode==OP_Lt || pOp[-1].opcode==OP_Gt );
  VdbeBranchTaken(cmpRes!=0, 2);
  if( cmpRes!=0 ) goto jump_to_p2;
  break;
}


/* Opcode: Permutation * * * P4 *
**
** Set the permutation used by the OP_Compare operator to be the array







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#ifdef SQLITE_DEBUG
  int nExtraDelete = 0;      /* Verifies FORDELETE and AUXDELETE flags */
#endif
  int rc = SQLITE_OK;        /* Value to return */
  sqlite3 *db = p->db;       /* The database */
  u8 resetSchemaOnFault = 0; /* Reset schema after an error if positive */
  u8 encoding = ENC(db);     /* The database encoding */
  int iCompare = 0;          /* Result of last comparison */
  unsigned nVmStep = 0;      /* Number of virtual machine steps */
#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
  unsigned nProgressLimit = 0;/* Invoke xProgress() when nVmStep reaches this */
#endif
  Mem *aMem = p->aMem;       /* Copy of p->aMem */
  Mem *pIn1 = 0;             /* 1st input operand */
  Mem *pIn2 = 0;             /* 2nd input operand */
  Mem *pIn3 = 0;             /* 3rd input operand */
  Mem *pOut = 0;             /* Output operand */
  int *aPermute = 0;         /* Permutation of columns for OP_Compare */
  i64 lastRowid = db->lastRowid;  /* Saved value of the last insert ROWID */

#ifdef VDBE_PROFILE
  u64 start;                 /* CPU clock count at start of opcode */
#endif
  /*** INSERT STACK UNION HERE ***/

  assert( p->magic==VDBE_MAGIC_RUN );  /* sqlite3_step() verifies this */
  sqlite3VdbeEnter(p);
................................................................................
      assert( pOp->opcode==OP_Eq || pOp->opcode==OP_Ne );
      assert( (flags1 & MEM_Cleared)==0 );
      assert( (pOp->p5 & SQLITE_JUMPIFNULL)==0 );
      if( (flags1&MEM_Null)!=0
       && (flags3&MEM_Null)!=0
       && (flags3&MEM_Cleared)==0
      ){
        iCompare = 0;  /* Operands are equal */
      }else{
        iCompare = 1;  /* Operands are not equal */
      }
    }else{
      /* SQLITE_NULLEQ is clear and at least one operand is NULL,
      ** then the result is always NULL.
      ** The jump is taken if the SQLITE_JUMPIFNULL bit is set.
      */
      iCompare = 1;    /* Operands are not equal */
      if( pOp->p5 & SQLITE_STOREP2 ){
        pOut = &aMem[pOp->p2];
        memAboutToChange(p, pOut);
        MemSetTypeFlag(pOut, MEM_Null);
        REGISTER_TRACE(pOp->p2, pOut);
      }else{
        VdbeBranchTaken(2,3);
................................................................................
      sqlite3VdbeMemExpandBlob(pIn1);
      flags1 &= ~MEM_Zero;
    }
    if( flags3 & MEM_Zero ){
      sqlite3VdbeMemExpandBlob(pIn3);
      flags3 &= ~MEM_Zero;
    }
    iCompare = sqlite3MemCompare(pIn3, pIn1, pOp->p4.pColl);
  }
  switch( pOp->opcode ){
    case OP_Eq:    res = iCompare==0;     break;
    case OP_Ne:    res = iCompare!=0;     break;
    case OP_Lt:    res = iCompare<0;      break;
    case OP_Le:    res = iCompare<=0;     break;
    case OP_Gt:    res = iCompare>0;      break;
    default:       res = iCompare>=0;     break;
  }

  /* Undo any changes made by applyAffinity() to the input registers. */
  assert( (pIn1->flags & MEM_Dyn) == (flags1 & MEM_Dyn) );
  pIn1->flags = flags1;
  assert( (pIn3->flags & MEM_Dyn) == (flags3 & MEM_Dyn) );
  pIn3->flags = flags3;
................................................................................
** operator and if the result of that Eq would be NULL or false (0), then
** then jump to P2.  If the result of comparing the two previous operands
** using Eq would have been true (1), then fall through.
*/
case OP_ElseNotEq: {       /* same as TK_ESCAPE, jump */
  assert( pOp>aOp );
  assert( pOp[-1].opcode==OP_Lt || pOp[-1].opcode==OP_Gt );
  VdbeBranchTaken(iCompare!=0, 2);
  if( iCompare!=0 ) goto jump_to_p2;
  break;
}


/* Opcode: Permutation * * * P4 *
**
** Set the permutation used by the OP_Compare operator to be the array