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Overview
Comment:Performance improvements on the main loop of the LEMON-generated parser.
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SHA3-256:fec1ebadeb9d6b55b19a1c159c543fd7ae67b3307c4caee4d2541bd783630e23
User & Date: drh 2018-04-21 22:40:08
Context
2018-04-23
00:25
Fix an unreachable branch associated with stack overflow in the LEMON-generated parser. check-in: e3064ba3 user: drh tags: trunk
2018-04-21
22:40
Performance improvements on the main loop of the LEMON-generated parser. check-in: fec1ebad user: drh tags: trunk
20:24
Enhance LEMON to track which symbols actually carry semantic content. Output the list of symbols that do not carry content at the end of the report, but do not (yet) do anything else with the information. check-in: dcf2bafc user: drh tags: trunk
Changes
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Changes to tool/lempar.c.

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}
#endif

/*
** Find the appropriate action for a parser given the terminal
** look-ahead token iLookAhead.
*/
static unsigned int yy_find_shift_action(
  yyParser *pParser,        /* The parser */
  YYCODETYPE iLookAhead     /* The look-ahead token */

){
  int i;
  int stateno = pParser->yytos->stateno;
 
  if( stateno>YY_MAX_SHIFT ) return stateno;
  assert( stateno <= YY_SHIFT_COUNT );
#if defined(YYCOVERAGE)
  yycoverage[stateno][iLookAhead] = 1;
#endif
  do{
    i = yy_shift_ofst[stateno];
................................................................................
}

/*
** Find the appropriate action for a parser given the non-terminal
** look-ahead token iLookAhead.
*/
static int yy_find_reduce_action(
  int stateno,              /* Current state number */
  YYCODETYPE iLookAhead     /* The look-ahead token */
){
  int i;
#ifdef YYERRORSYMBOL
  if( stateno>YY_REDUCE_COUNT ){
    return yy_default[stateno];
  }
................................................................................
#endif

/*
** Perform a shift action.
*/
static void yy_shift(
  yyParser *yypParser,          /* The parser to be shifted */
  int yyNewState,               /* The new state to shift in */
  int yyMajor,                  /* The major token to shift in */
  ParseTOKENTYPE yyMinor        /* The minor token to shift in */
){
  yyStackEntry *yytos;
  yypParser->yytos++;
#ifdef YYTRACKMAXSTACKDEPTH
  if( (int)(yypParser->yytos - yypParser->yystack)>yypParser->yyhwm ){
    yypParser->yyhwm++;
................................................................................
    }
  }
#endif
  if( yyNewState > YY_MAX_SHIFT ){
    yyNewState += YY_MIN_REDUCE - YY_MIN_SHIFTREDUCE;
  }
  yytos = yypParser->yytos;
  yytos->stateno = (YYACTIONTYPE)yyNewState;
  yytos->major = (YYCODETYPE)yyMajor;
  yytos->minor.yy0 = yyMinor;
  yyTraceShift(yypParser, yyNewState, "Shift");
}

/* The following table contains information about every rule that
** is used during the reduce.
*/
................................................................................
**
** The yyLookahead and yyLookaheadToken parameters provide reduce actions
** access to the lookahead token (if any).  The yyLookahead will be YYNOCODE
** if the lookahead token has already been consumed.  As this procedure is
** only called from one place, optimizing compilers will in-line it, which
** means that the extra parameters have no performance impact.
*/
static void yy_reduce(
  yyParser *yypParser,         /* The parser */
  unsigned int yyruleno,       /* Number of the rule by which to reduce */
  int yyLookahead,             /* Lookahead token, or YYNOCODE if none */
  ParseTOKENTYPE yyLookaheadToken  /* Value of the lookahead token */
  ParseCTX_PDECL                   /* %extra_context */
){
  int yygoto;                     /* The next state */
................................................................................
      yypParser->yyhwm++;
      assert( yypParser->yyhwm == (int)(yypParser->yytos - yypParser->yystack));
    }
#endif
#if YYSTACKDEPTH>0 
    if( yypParser->yytos>=yypParser->yystackEnd ){
      yyStackOverflow(yypParser);
      return;
    }
#else
    if( yypParser->yytos>=&yypParser->yystack[yypParser->yystksz-1] ){
      if( yyGrowStack(yypParser) ){
        yyStackOverflow(yypParser);
        return;
      }
      yymsp = yypParser->yytos;
    }
#endif
  }

  switch( yyruleno ){
................................................................................
  assert( yyact!=YY_ERROR_ACTION );

  yymsp += yysize+1;
  yypParser->yytos = yymsp;
  yymsp->stateno = (YYACTIONTYPE)yyact;
  yymsp->major = (YYCODETYPE)yygoto;
  yyTraceShift(yypParser, yyact, "... then shift");

}

/*
** The following code executes when the parse fails
*/
#ifndef YYNOERRORRECOVERY
static void yy_parse_failed(
................................................................................
void Parse(
  void *yyp,                   /* The parser */
  int yymajor,                 /* The major token code number */
  ParseTOKENTYPE yyminor       /* The value for the token */
  ParseARG_PDECL               /* Optional %extra_argument parameter */
){
  YYMINORTYPE yyminorunion;
  unsigned int yyact;   /* The parser action. */
#if !defined(YYERRORSYMBOL) && !defined(YYNOERRORRECOVERY)
  int yyendofinput;     /* True if we are at the end of input */
#endif
#ifdef YYERRORSYMBOL
  int yyerrorhit = 0;   /* True if yymajor has invoked an error */
#endif
  yyParser *yypParser = (yyParser*)yyp;  /* The parser */
................................................................................
  ParseARG_STORE

  assert( yypParser->yytos!=0 );
#if !defined(YYERRORSYMBOL) && !defined(YYNOERRORRECOVERY)
  yyendofinput = (yymajor==0);
#endif


#ifndef NDEBUG
  if( yyTraceFILE ){
    int stateno = yypParser->yytos->stateno;
    if( stateno < YY_MIN_REDUCE ){
      fprintf(yyTraceFILE,"%sInput '%s' in state %d\n",
              yyTracePrompt,yyTokenName[yymajor],stateno);
    }else{
      fprintf(yyTraceFILE,"%sInput '%s' with pending reduce %d\n",
              yyTracePrompt,yyTokenName[yymajor],stateno-YY_MIN_REDUCE);
    }
  }
#endif

  do{

    yyact = yy_find_shift_action(yypParser,(YYCODETYPE)yymajor);
    if( yyact >= YY_MIN_REDUCE ){
      yy_reduce(yypParser,yyact-YY_MIN_REDUCE,yymajor,yyminor ParseCTX_PARAM);

    }else if( yyact <= YY_MAX_SHIFTREDUCE ){
      yy_shift(yypParser,yyact,yymajor,yyminor);
#ifndef YYNOERRORRECOVERY
      yypParser->yyerrcnt--;
#endif
      yymajor = YYNOCODE;
    }else if( yyact==YY_ACCEPT_ACTION ){





      yypParser->yytos--;
      yy_accept(yypParser);

      return;
    }else{
      assert( yyact == YY_ERROR_ACTION );
      yyminorunion.yy0 = yyminor;
#ifdef YYERRORSYMBOL
      int yymx;
#endif
................................................................................
          yymajor = YYNOCODE;
        }else if( yymx!=YYERRORSYMBOL ){
          yy_shift(yypParser,yyact,YYERRORSYMBOL,yyminor);
        }
      }
      yypParser->yyerrcnt = 3;
      yyerrorhit = 1;


#elif defined(YYNOERRORRECOVERY)
      /* If the YYNOERRORRECOVERY macro is defined, then do not attempt to
      ** do any kind of error recovery.  Instead, simply invoke the syntax
      ** error routine and continue going as if nothing had happened.
      **
      ** Applications can set this macro (for example inside %include) if
      ** they intend to abandon the parse upon the first syntax error seen.
      */
      yy_syntax_error(yypParser,yymajor, yyminor);
      yy_destructor(yypParser,(YYCODETYPE)yymajor,&yyminorunion);
      yymajor = YYNOCODE;
      
#else  /* YYERRORSYMBOL is not defined */
      /* This is what we do if the grammar does not define ERROR:
      **
      **  * Report an error message, and throw away the input token.
      **
      **  * If the input token is $, then fail the parse.
      **
................................................................................
      yy_destructor(yypParser,(YYCODETYPE)yymajor,&yyminorunion);
      if( yyendofinput ){
        yy_parse_failed(yypParser);
#ifndef YYNOERRORRECOVERY
        yypParser->yyerrcnt = -1;
#endif
      }
      yymajor = YYNOCODE;
#endif
    }
  }while( yymajor!=YYNOCODE && yypParser->yytos>yypParser->yystack );
#ifndef NDEBUG
  if( yyTraceFILE ){
    yyStackEntry *i;
    char cDiv = '[';
    fprintf(yyTraceFILE,"%sReturn. Stack=",yyTracePrompt);
    for(i=&yypParser->yystack[1]; i<=yypParser->yytos; i++){
      fprintf(yyTraceFILE,"%c%s", cDiv, yyTokenName[i->major]);







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}
#endif

/*
** Find the appropriate action for a parser given the terminal
** look-ahead token iLookAhead.
*/
static YYACTIONTYPE yy_find_shift_action(

  YYCODETYPE iLookAhead,    /* The look-ahead token */
  YYACTIONTYPE stateno      /* Current state number */
){
  int i;


  if( stateno>YY_MAX_SHIFT ) return stateno;
  assert( stateno <= YY_SHIFT_COUNT );
#if defined(YYCOVERAGE)
  yycoverage[stateno][iLookAhead] = 1;
#endif
  do{
    i = yy_shift_ofst[stateno];
................................................................................
}

/*
** Find the appropriate action for a parser given the non-terminal
** look-ahead token iLookAhead.
*/
static int yy_find_reduce_action(
  YYACTIONTYPE stateno,     /* Current state number */
  YYCODETYPE iLookAhead     /* The look-ahead token */
){
  int i;
#ifdef YYERRORSYMBOL
  if( stateno>YY_REDUCE_COUNT ){
    return yy_default[stateno];
  }
................................................................................
#endif

/*
** Perform a shift action.
*/
static void yy_shift(
  yyParser *yypParser,          /* The parser to be shifted */
  YYACTIONTYPE yyNewState,      /* The new state to shift in */
  YYCODETYPE yyMajor,           /* The major token to shift in */
  ParseTOKENTYPE yyMinor        /* The minor token to shift in */
){
  yyStackEntry *yytos;
  yypParser->yytos++;
#ifdef YYTRACKMAXSTACKDEPTH
  if( (int)(yypParser->yytos - yypParser->yystack)>yypParser->yyhwm ){
    yypParser->yyhwm++;
................................................................................
    }
  }
#endif
  if( yyNewState > YY_MAX_SHIFT ){
    yyNewState += YY_MIN_REDUCE - YY_MIN_SHIFTREDUCE;
  }
  yytos = yypParser->yytos;
  yytos->stateno = yyNewState;
  yytos->major = yyMajor;
  yytos->minor.yy0 = yyMinor;
  yyTraceShift(yypParser, yyNewState, "Shift");
}

/* The following table contains information about every rule that
** is used during the reduce.
*/
................................................................................
**
** The yyLookahead and yyLookaheadToken parameters provide reduce actions
** access to the lookahead token (if any).  The yyLookahead will be YYNOCODE
** if the lookahead token has already been consumed.  As this procedure is
** only called from one place, optimizing compilers will in-line it, which
** means that the extra parameters have no performance impact.
*/
static YYACTIONTYPE yy_reduce(
  yyParser *yypParser,         /* The parser */
  unsigned int yyruleno,       /* Number of the rule by which to reduce */
  int yyLookahead,             /* Lookahead token, or YYNOCODE if none */
  ParseTOKENTYPE yyLookaheadToken  /* Value of the lookahead token */
  ParseCTX_PDECL                   /* %extra_context */
){
  int yygoto;                     /* The next state */
................................................................................
      yypParser->yyhwm++;
      assert( yypParser->yyhwm == (int)(yypParser->yytos - yypParser->yystack));
    }
#endif
#if YYSTACKDEPTH>0 
    if( yypParser->yytos>=yypParser->yystackEnd ){
      yyStackOverflow(yypParser);
      return YY_ACCEPT_ACTION;
    }
#else
    if( yypParser->yytos>=&yypParser->yystack[yypParser->yystksz-1] ){
      if( yyGrowStack(yypParser) ){
        yyStackOverflow(yypParser);
        return YY_ACCEPT_ACTION;
      }
      yymsp = yypParser->yytos;
    }
#endif
  }

  switch( yyruleno ){
................................................................................
  assert( yyact!=YY_ERROR_ACTION );

  yymsp += yysize+1;
  yypParser->yytos = yymsp;
  yymsp->stateno = (YYACTIONTYPE)yyact;
  yymsp->major = (YYCODETYPE)yygoto;
  yyTraceShift(yypParser, yyact, "... then shift");
  return yyact;
}

/*
** The following code executes when the parse fails
*/
#ifndef YYNOERRORRECOVERY
static void yy_parse_failed(
................................................................................
void Parse(
  void *yyp,                   /* The parser */
  int yymajor,                 /* The major token code number */
  ParseTOKENTYPE yyminor       /* The value for the token */
  ParseARG_PDECL               /* Optional %extra_argument parameter */
){
  YYMINORTYPE yyminorunion;
  YYACTIONTYPE yyact;   /* The parser action. */
#if !defined(YYERRORSYMBOL) && !defined(YYNOERRORRECOVERY)
  int yyendofinput;     /* True if we are at the end of input */
#endif
#ifdef YYERRORSYMBOL
  int yyerrorhit = 0;   /* True if yymajor has invoked an error */
#endif
  yyParser *yypParser = (yyParser*)yyp;  /* The parser */
................................................................................
  ParseARG_STORE

  assert( yypParser->yytos!=0 );
#if !defined(YYERRORSYMBOL) && !defined(YYNOERRORRECOVERY)
  yyendofinput = (yymajor==0);
#endif

  yyact = yypParser->yytos->stateno;
#ifndef NDEBUG
  if( yyTraceFILE ){

    if( yyact < YY_MIN_REDUCE ){
      fprintf(yyTraceFILE,"%sInput '%s' in state %d\n",
              yyTracePrompt,yyTokenName[yymajor],yyact);
    }else{
      fprintf(yyTraceFILE,"%sInput '%s' with pending reduce %d\n",
              yyTracePrompt,yyTokenName[yymajor],yyact-YY_MIN_REDUCE);
    }
  }
#endif

  do{
    assert( yyact==yypParser->yytos->stateno );
    yyact = yy_find_shift_action(yymajor,yyact);
    if( yyact >= YY_MIN_REDUCE ){
      yyact = yy_reduce(yypParser,yyact-YY_MIN_REDUCE,yymajor,
                        yyminor ParseCTX_PARAM);
    }else if( yyact <= YY_MAX_SHIFTREDUCE ){
      yy_shift(yypParser,yyact,yymajor,yyminor);
#ifndef YYNOERRORRECOVERY
      yypParser->yyerrcnt--;
#endif
      break;
    }else if( yyact==YY_ACCEPT_ACTION ){
      /* YY_ACCEPT_ACTION also happens on a stack overflow.  We distingush
      ** the two cases by observing that on a true accept, there should be
      ** a single token left on the stack, whereas on a stack overflow,
      ** the stack has been popped (by yyStackOverflow()) to be empty */
      if( yypParser->yytos > yypParser->yystack ){
        yypParser->yytos--;
        yy_accept(yypParser);
      }
      return;
    }else{
      assert( yyact == YY_ERROR_ACTION );
      yyminorunion.yy0 = yyminor;
#ifdef YYERRORSYMBOL
      int yymx;
#endif
................................................................................
          yymajor = YYNOCODE;
        }else if( yymx!=YYERRORSYMBOL ){
          yy_shift(yypParser,yyact,YYERRORSYMBOL,yyminor);
        }
      }
      yypParser->yyerrcnt = 3;
      yyerrorhit = 1;
      if( yymajor==YYNOCODE ) break;
      yyact = yypParser->yytos->stateno;
#elif defined(YYNOERRORRECOVERY)
      /* If the YYNOERRORRECOVERY macro is defined, then do not attempt to
      ** do any kind of error recovery.  Instead, simply invoke the syntax
      ** error routine and continue going as if nothing had happened.
      **
      ** Applications can set this macro (for example inside %include) if
      ** they intend to abandon the parse upon the first syntax error seen.
      */
      yy_syntax_error(yypParser,yymajor, yyminor);
      yy_destructor(yypParser,(YYCODETYPE)yymajor,&yyminorunion);
      break;

#else  /* YYERRORSYMBOL is not defined */
      /* This is what we do if the grammar does not define ERROR:
      **
      **  * Report an error message, and throw away the input token.
      **
      **  * If the input token is $, then fail the parse.
      **
................................................................................
      yy_destructor(yypParser,(YYCODETYPE)yymajor,&yyminorunion);
      if( yyendofinput ){
        yy_parse_failed(yypParser);
#ifndef YYNOERRORRECOVERY
        yypParser->yyerrcnt = -1;
#endif
      }
      break;
#endif
    }
  }while( yypParser->yytos>yypParser->yystack );
#ifndef NDEBUG
  if( yyTraceFILE ){
    yyStackEntry *i;
    char cDiv = '[';
    fprintf(yyTraceFILE,"%sReturn. Stack=",yyTracePrompt);
    for(i=&yypParser->yystack[1]; i<=yypParser->yytos; i++){
      fprintf(yyTraceFILE,"%c%s", cDiv, yyTokenName[i->major]);