rusefi
/
lua
mirror of https://github.com/rusefi/lua.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Removed optimization for «if ... then goto» 

That optimization was too complex and caused some weird traces when
debugging. The more common case «if ... then break» was kept.
This commit is contained in:
Roberto Ierusalimschy 2020-11-11 14:41:41 -03:00
parent d282652561
commit ab1aca94e8
2 changed files with 6 additions and 66 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

50
lparser.c
View File

@ -1623,59 +1623,21 @@ static void forstat (LexState *ls, int line) {
}
/*
** Check whether next instruction is a single jump (a 'break', a 'goto'
** to a forward label, or a 'goto' to a backward label with no variable
** to close). If so, set the name of the 'label' it is jumping to
** ("break" for a 'break') or to where it is jumping to ('target') and
** return true. If not a single jump, leave input unchanged, to be
** handled as a regular statement.
*/
static int issinglejump (LexState *ls, TString **label, int *target) {
if (testnext(ls, TK_BREAK)) { /* a break? */
*label = luaS_newliteral(ls->L, "break");
return 1;
}
else if (ls->t.token != TK_GOTO || luaX_lookahead(ls) != TK_NAME)
return 0; /* not a valid goto */
else {
TString *lname = ls->lookahead.seminfo.ts; /* label's id */
Labeldesc *lb = findlabel(ls, lname);
if (lb) { /* a backward jump? */
/* does it need to close variables? */
if (luaY_nvarstack(ls->fs) > stacklevel(ls->fs, lb->nactvar))
return 0; /* not a single jump; cannot optimize */
*target = lb->pc;
}
else /* jump forward */
*label = lname;
luaX_next(ls); /* skip goto */
luaX_next(ls); /* skip name */
return 1;
}
}
static void test_then_block (LexState *ls, int *escapelist) {
/* test_then_block -> [IF | ELSEIF] cond THEN block */
BlockCnt bl;
int line;
FuncState *fs = ls->fs;
TString *jlb = NULL;
int target = NO_JUMP;
expdesc v;
int jf; /* instruction to skip 'then' code (if condition is false) */
luaX_next(ls); /* skip IF or ELSEIF */
expr(ls, &v); /* read condition */
checknext(ls, TK_THEN);
line = ls->linenumber;
if (issinglejump(ls, &jlb, &target)) { /* 'if x then goto' ? */
luaK_goiffalse(ls->fs, &v); /* will jump to label if condition is true */
if (ls->t.token == TK_BREAK) { /* 'if x then break' ? */
int line = ls->linenumber;
luaK_goiffalse(ls->fs, &v); /* will jump if condition is true */
luaX_next(ls); /* skip 'break' */
enterblock(fs, &bl, 0); /* must enter block before 'goto' */
if (jlb != NULL) /* forward jump? */
newgotoentry(ls, jlb, line, v.t); /* will be resolved later */
else /* backward jump */
luaK_patchlist(fs, v.t, target); /* jump directly to 'target' */
newgotoentry(ls, luaS_newliteral(ls->L, "break"), line, v.t);
while (testnext(ls, ';')) {} /* skip semicolons */
if (block_follow(ls, 0)) { /* jump is the entire block? */
leaveblock(fs);
@ -1684,7 +1646,7 @@ static void test_then_block (LexState *ls, int *escapelist) {
else /* must skip over 'then' part if condition is false */
jf = luaK_jump(fs);
}
else { /* regular case (not a jump) */
else { /* regular case (not a break) */
luaK_goiftrue(ls->fs, &v); /* skip over block if condition is false */
enterblock(fs, &bl, 0);
jf = v.f;

22
testes/code.lua
View File

@ -392,28 +392,6 @@ check(function (a, b)
end,
'TEST', 'JMP', 'TEST', 'JMP', 'ADDI', 'MMBINI', 'JMP', 'RETURN0')
checkequal(
function (a) while a < 10 do a = a + 1 end end,
function (a)
::loop::
if not (a < 10) then goto exit end
a = a + 1
goto loop
::exit::
end
)
checkequal(
function (a) repeat local x = a + 1; a = x until a > 0 end,
function (a)
::loop:: do
local x = a + 1
a = x
end
if not (a > 0) then goto loop end
end
)
checkequal(function () return 6 or true or nil end,
function () return k6 or kTrue or kNil end)