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optimization for |if cond then goto|

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This commit is contained in:
Roberto Ierusalimschy 2011-08-30 13:38:58 -03:00
parent ca458f1f52
commit c8f47c2934
1 changed files with 37 additions and 18 deletions
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55
lparser.c
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@ -1,5 +1,5 @@
/*
** $Id: lparser.c,v 2.116 2011/08/23 17:24:34 roberto Exp roberto $
** $Id: lparser.c,v 2.117 2011/08/25 13:45:24 roberto Exp roberto $
** Lua Parser
** See Copyright Notice in lua.h
*/
@ -383,7 +383,8 @@ static int findlabel (LexState *ls, int g) {
static int newlabelentry (LexState *ls, Labellist *l, TString *name,
int line, int pc) {
int n = l->n;
luaM_growvector(ls->L, l->arr, n, l->size, Labeldesc, SHRT_MAX, "labels");
luaM_growvector(ls->L, l->arr, n, l->size,
Labeldesc, SHRT_MAX, "labels/gotos");
l->arr[n].name = name;
l->arr[n].line = line;
l->arr[n].nactvar = ls->fs->nactvar;
@ -1178,10 +1179,18 @@ static int cond (LexState *ls) {
}
static void gotostat (LexState *ls, TString *label, int line) {
/* create new entry for this goto */
int g = newlabelentry(ls, &ls->dyd->gt, label, line, luaK_jump(ls->fs));
findlabel(ls, g);
static void gotostat (LexState *ls, int pc) {
int line = ls->linenumber;
TString *label;
int g;
if (testnext(ls, TK_GOTO))
label = str_checkname(ls);
else {
luaX_next(ls); /* skip break */
label = luaS_new(ls->L, "break");
}
g = newlabelentry(ls, &ls->dyd->gt, label, line, pc);
findlabel(ls, g); /* close it if label already defined */
}
@ -1362,16 +1371,32 @@ static void forstat (LexState *ls, int line) {
static void test_then_block (LexState *ls, int *escapelist) {
/* test_then_block -> [IF | ELSEIF] cond THEN block */
BlockCnt bl;
FuncState *fs = ls->fs;
int condexit;
expdesc v;
int jf; /* instruction to skip 'then' code (if condition is false) */
luaX_next(ls); /* skip IF or ELSEIF */
condexit = cond(ls); /* 'if' condition */
enterblock(fs, &bl, 0);
expr(ls, &v); /* read condition */
checknext(ls, TK_THEN);
block(ls); /* `then' part */
if (ls->t.token == TK_GOTO || ls->t.token == TK_BREAK) {
luaK_goiffalse(ls->fs, &v); /* will jump to label if condition is true */
gotostat(ls, v.t); /* handle goto/break */
if (block_follow(ls, 0)) /* no more code after 'goto'? */
goto leave; /* that is it */
else /* must skip over 'then' part if condition is false */
jf = luaK_jump(fs);
}
else { /* regular case (not goto/break) */
luaK_goiftrue(ls->fs, &v); /* skip over block if condition is false */
jf = v.f;
}
statlist(ls); /* `then' part */
if (ls->t.token == TK_ELSE ||
ls->t.token == TK_ELSEIF) /* followed by 'else'/'elseif'? */
luaK_concat(fs, escapelist, luaK_jump(fs)); /* must jump over it */
luaK_patchtohere(fs, condexit); /* 'if' condition jumps to here */
luaK_patchtohere(fs, jf);
leave: leaveblock(fs);
}
@ -1545,15 +1570,9 @@ static void statement (LexState *ls) {
retstat(ls);
break;
}
case TK_BREAK: { /* stat -> breakstat */
luaX_next(ls); /* skip BREAK */
/* code it as "goto 'break'" */
gotostat(ls, luaS_new(ls->L, "break"), line);
break;
}
case TK_BREAK: /* stat -> breakstat */
case TK_GOTO: { /* stat -> 'goto' NAME */
luaX_next(ls); /* skip GOTO */
gotostat(ls, str_checkname(ls), line);
gotostat(ls, luaK_jump(ls->fs));
break;
}
default: { /* stat -> func | assignment */