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Overview
Comment:Increase the size of the yy_lookahead table so that it is never necessary to down bounds checking on the index.
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SHA3-256: bafd872398e58766e996963372c7acc03a1e20a6d39a3867ca45d3ea0ed2ac1d
User & Date: drh 2019-08-28 02:09:47.441
Context
2019-08-28
11:31
Further improvements to parser speed by enlarging lookup tables to eliminate the need to do range checking on the index prior to lookup. (check-in: 47d3e091ae user: drh tags: lemon-optimization)
02:09
Increase the size of the yy_lookahead table so that it is never necessary to down bounds checking on the index. (check-in: bafd872398 user: drh tags: lemon-optimization)
2019-08-27
19:59
Add support for "ORDER BY ... NULLS FIRST" and "ORDER BY ... NULLS LAST". Use this to fix ticket [f8a7060e]. (check-in: 94085fb3e7 user: dan tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to tool/lemon.c.
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  char line[LINESIZE];
  int  lineno;
  struct state *stp;
  struct action *ap;
  struct rule *rp;
  struct acttab *pActtab;
  int i, j, n, sz;

  int szActionType;     /* sizeof(YYACTIONTYPE) */
  int szCodeType;       /* sizeof(YYCODETYPE)   */
  const char *name;
  int mnTknOfst, mxTknOfst;
  int mnNtOfst, mxNtOfst;
  struct axset *ax;









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  char line[LINESIZE];
  int  lineno;
  struct state *stp;
  struct action *ap;
  struct rule *rp;
  struct acttab *pActtab;
  int i, j, n, sz;
  int nLookAhead;
  int szActionType;     /* sizeof(YYACTIONTYPE) */
  int szCodeType;       /* sizeof(YYCODETYPE)   */
  const char *name;
  int mnTknOfst, mxTknOfst;
  int mnNtOfst, mxNtOfst;
  struct axset *ax;
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  lemp->tablesize += n*szCodeType;
  fprintf(out,"static const YYCODETYPE yy_lookahead[] = {\n"); lineno++;
  for(i=j=0; i<n; i++){
    int la = acttab_yylookahead(pActtab, i);
    if( la<0 ) la = lemp->nsymbol;
    if( j==0 ) fprintf(out," /* %5d */ ", i);
    fprintf(out, " %4d,", la);
    if( j==9 || i==n-1 ){














      fprintf(out, "\n"); lineno++;
      j = 0;
    }else{
      j++;
    }

  }

  fprintf(out, "};\n"); lineno++;

  /* Output the yy_shift_ofst[] table */
  n = lemp->nxstate;
  while( n>0 && lemp->sorted[n-1]->iTknOfst==NO_OFFSET ) n--;
  fprintf(out, "#define YY_SHIFT_COUNT    (%d)\n", n-1); lineno++;
  fprintf(out, "#define YY_SHIFT_MIN      (%d)\n", mnTknOfst); lineno++;








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  lemp->tablesize += n*szCodeType;
  fprintf(out,"static const YYCODETYPE yy_lookahead[] = {\n"); lineno++;
  for(i=j=0; i<n; i++){
    int la = acttab_yylookahead(pActtab, i);
    if( la<0 ) la = lemp->nsymbol;
    if( j==0 ) fprintf(out," /* %5d */ ", i);
    fprintf(out, " %4d,", la);
    if( j==9 ){
      fprintf(out, "\n"); lineno++;
      j = 0;
    }else{
      j++;
    }
  }
  /* Add extra entries to the end of the yy_lookahead[] table so that
  ** yy_shift_ofst[]+iToken will always be a valid index into the array,
  ** even for the largest possible value of yy_shift_ofst[] and iToken. */
  nLookAhead = lemp->nterminal + lemp->nactiontab;
  while( i<nLookAhead ){
    if( j==0 ) fprintf(out," /* %5d */ ", i);
    fprintf(out, " %4d,", lemp->nterminal);
    if( j==9 ){
      fprintf(out, "\n"); lineno++;
      j = 0;
    }else{
      j++;
    }
    i++;
  }
  if( j>0 ) fprintf(out, "\n"); lineno++;
  fprintf(out, "};\n"); lineno++;

  /* Output the yy_shift_ofst[] table */
  n = lemp->nxstate;
  while( n>0 && lemp->sorted[n-1]->iTknOfst==NO_OFFSET ) n--;
  fprintf(out, "#define YY_SHIFT_COUNT    (%d)\n", n-1); lineno++;
  fprintf(out, "#define YY_SHIFT_MIN      (%d)\n", mnTknOfst); lineno++;
︙︙
Changes to tool/lempar.c.
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  assert( stateno <= YY_SHIFT_COUNT );
#if defined(YYCOVERAGE)
  yycoverage[stateno][iLookAhead] = 1;
#endif
  do{
    i = yy_shift_ofst[stateno];
    assert( i>=0 );

    /* assert( i+YYNTOKEN<=(int)YY_NLOOKAHEAD ); */
    assert( iLookAhead!=YYNOCODE );
    assert( iLookAhead < YYNTOKEN );
    i += iLookAhead;

    if( i>=YY_NLOOKAHEAD || yy_lookahead[i]!=iLookAhead ){
#ifdef YYFALLBACK
      YYCODETYPE iFallback;            /* Fallback token */
      if( iLookAhead<sizeof(yyFallback)/sizeof(yyFallback[0])
             && (iFallback = yyFallback[iLookAhead])!=0 ){
#ifndef NDEBUG
        if( yyTraceFILE ){
          fprintf(yyTraceFILE, "%sFALLBACK %s => %s\n",








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  assert( stateno <= YY_SHIFT_COUNT );
#if defined(YYCOVERAGE)
  yycoverage[stateno][iLookAhead] = 1;
#endif
  do{
    i = yy_shift_ofst[stateno];
    assert( i>=0 );
    assert( i<=YY_ACTTAB_COUNT );
    assert( i+YYNTOKEN<=(int)YY_NLOOKAHEAD );
    assert( iLookAhead!=YYNOCODE );
    assert( iLookAhead < YYNTOKEN );
    i += iLookAhead;
    assert( i<(int)YY_NLOOKAHEAD );
    if( yy_lookahead[i]!=iLookAhead ){
#ifdef YYFALLBACK
      YYCODETYPE iFallback;            /* Fallback token */
      if( iLookAhead<sizeof(yyFallback)/sizeof(yyFallback[0])
             && (iFallback = yyFallback[iLookAhead])!=0 ){
#ifndef NDEBUG
        if( yyTraceFILE ){
          fprintf(yyTraceFILE, "%sFALLBACK %s => %s\n",
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