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In the lemon-generated parser, store the number of symbols on the RHS of each

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rule as a negative number and add it to the stack pointer, rather than storing
the value as a positive and subtracting it.  This makes the parser faster.

FossilOrigin-Name: b362f0d8ed34839bf3b29d10ed0853ab94245fba135ccd28e619caa6ee6992d5
This commit is contained in:
drh
2017-06-28 13:47:56 +00:00
parent bd8fcc130a
commit 6be95366c7
4 changed files with 15 additions and 15 deletions
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12
tool/lempar.c
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@ -635,8 +635,8 @@ static void yy_shift(
** is used during the reduce.
*/
static const struct {
YYCODETYPE lhs; /* Symbol on the left-hand side of the rule */
unsigned char nrhs; /* Number of right-hand side symbols in the rule */
YYCODETYPE lhs; /* Symbol on the left-hand side of the rule */
signed char nrhs; /* Negative of the number of RHS symbols in the rule */
} yyRuleInfo[] = {
%%
};
@ -661,7 +661,7 @@ static void yy_reduce(
if( yyTraceFILE && yyruleno<(int)(sizeof(yyRuleName)/sizeof(yyRuleName[0])) ){
yysize = yyRuleInfo[yyruleno].nrhs;
fprintf(yyTraceFILE, "%sReduce [%s], go to state %d.\n", yyTracePrompt,
yyRuleName[yyruleno], yymsp[-yysize].stateno);
yyRuleName[yyruleno], yymsp[yysize].stateno);
}
#endif /* NDEBUG */
@ -707,7 +707,7 @@ static void yy_reduce(
assert( yyruleno<sizeof(yyRuleInfo)/sizeof(yyRuleInfo[0]) );
yygoto = yyRuleInfo[yyruleno].lhs;
yysize = yyRuleInfo[yyruleno].nrhs;
yyact = yy_find_reduce_action(yymsp[-yysize].stateno,(YYCODETYPE)yygoto);
yyact = yy_find_reduce_action(yymsp[yysize].stateno,(YYCODETYPE)yygoto);
/* There are no SHIFTREDUCE actions on nonterminals because the table
** generator has simplified them to pure REDUCE actions. */
@ -717,10 +717,10 @@ static void yy_reduce(
assert( yyact!=YY_ERROR_ACTION );
if( yyact==YY_ACCEPT_ACTION ){
yypParser->yytos -= yysize;
yypParser->yytos += yysize;
yy_accept(yypParser);
}else{
yymsp -= yysize-1;
yymsp += yysize+1;
yypParser->yytos = yymsp;
yymsp->stateno = (YYACTIONTYPE)yyact;
yymsp->major = (YYCODETYPE)yygoto;