commit 7d4c7ae2af686df4a9f3cc0c6110986d886d55e6
parent 873588dc5f04bfc37006c3dc6ceb9a495ea503f2
Author: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Thu, 22 Dec 2022 13:52:26 -0300
Changes in opcodes for generic 'for'
Again, as the control variable is read only, the code doesn't need
to keep an internal copy of it.
Diffstat:
3 files changed, 38 insertions(+), 29 deletions(-)
diff --git a/lparser.c b/lparser.c
@@ -1558,6 +1558,7 @@ static void forbody (LexState *ls, int base, int line, int nvars, int isgen) {
int prep, endfor;
checknext(ls, TK_DO);
prep = luaK_codeABx(fs, forprep[isgen], base, 0);
+ fs->freereg--; /* both 'forprep' remove one register from the stack */
enterblock(fs, &bl, 0); /* scope for declared variables */
adjustlocalvars(ls, nvars);
luaK_reserveregs(fs, nvars);
@@ -1591,8 +1592,7 @@ static void fornum (LexState *ls, TString *varname, int line) {
luaK_int(fs, fs->freereg, 1);
luaK_reserveregs(fs, 1);
}
- adjustlocalvars(ls, 2); /* start scope for internal state variables */
- fs->freereg--; /* OP_FORPREP removes one register from the stack */
+ adjustlocalvars(ls, 2); /* start scope for internal variables */
forbody(ls, base, line, 1, 0);
}
@@ -1601,14 +1601,13 @@ static void forlist (LexState *ls, TString *indexname) {
/* forlist -> NAME {,NAME} IN explist forbody */
FuncState *fs = ls->fs;
expdesc e;
- int nvars = 5; /* gen, state, control, toclose, 'indexname' */
+ int nvars = 4; /* function, state, closing, control */
int line;
int base = fs->freereg;
- /* create control variables */
- new_localvarliteral(ls, "(for state)");
- new_localvarliteral(ls, "(for state)");
- new_localvarliteral(ls, "(for state)");
- new_localvarliteral(ls, "(for state)");
+ /* create internal variables */
+ new_localvarliteral(ls, "(for state)"); /* iterator function */
+ new_localvarliteral(ls, "(for state)"); /* state */
+ new_localvarliteral(ls, "(for state)"); /* closing var. (after swap) */
new_localvarkind(ls, indexname, RDKCONST); /* control variable */
/* other declared variables */
while (testnext(ls, ',')) {
@@ -1618,10 +1617,10 @@ static void forlist (LexState *ls, TString *indexname) {
checknext(ls, TK_IN);
line = ls->linenumber;
adjust_assign(ls, 4, explist(ls, &e), &e);
- adjustlocalvars(ls, 4); /* control variables */
- marktobeclosed(fs); /* last control var. must be closed */
- luaK_checkstack(fs, 3); /* extra space to call generator */
- forbody(ls, base, line, nvars - 4, 1);
+ adjustlocalvars(ls, 3); /* start scope for internal variables */
+ marktobeclosed(fs); /* last internal var. must be closed */
+ luaK_checkstack(fs, 2); /* extra space to call iterator */
+ forbody(ls, base, line, nvars - 3, 1);
}
diff --git a/lvm.c b/lvm.c
@@ -1806,26 +1806,38 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
vmbreak;
}
vmcase(OP_TFORPREP) {
+ /* before: 'ra' has the iterator function, 'ra + 1' has the state,
+ 'ra + 2' has the initial value for the control variable, and
+ 'ra + 3' has the closing variable. This opcode then swaps the
+ control and the closing variables and marks the closing variable
+ as to-be-closed.
+ */
StkId ra = RA(i);
- /* create to-be-closed upvalue (if needed) */
- halfProtect(luaF_newtbcupval(L, ra + 3));
- pc += GETARG_Bx(i);
- i = *(pc++); /* go to next instruction */
+ TValue temp; /* to swap control and closing variables */
+ setobj(L, &temp, s2v(ra + 3));
+ setobjs2s(L, ra + 3, ra + 2);
+ setobj2s(L, ra + 2, &temp);
+ /* create to-be-closed upvalue (if closing var. is not nil) */
+ halfProtect(luaF_newtbcupval(L, ra + 2));
+ pc += GETARG_Bx(i); /* go to end of the loop */
+ i = *(pc++); /* fetch next instruction */
lua_assert(GET_OPCODE(i) == OP_TFORCALL && ra == RA(i));
goto l_tforcall;
}
vmcase(OP_TFORCALL) {
l_tforcall: {
- StkId ra = RA(i);
/* 'ra' has the iterator function, 'ra + 1' has the state,
- 'ra + 2' has the control variable, and 'ra + 3' has the
- to-be-closed variable. The call will use the stack after
- these values (starting at 'ra + 4')
+ 'ra + 2' has the closing variable, and 'ra + 3' has the control
+ variable. The call will use the stack starting at 'ra + 3',
+ so that it preserves the first three values, and the first
+ return will be the new value for the control variable.
*/
- /* push function, state, and control variable */
- memcpy(ra + 4, ra, 3 * sizeof(*ra));
- L->top.p = ra + 4 + 3;
- ProtectNT(luaD_call(L, ra + 4, GETARG_C(i))); /* do the call */
+ StkId ra = RA(i);
+ setobjs2s(L, ra + 5, ra + 3); /* copy the control variable */
+ setobjs2s(L, ra + 4, ra + 1); /* copy state */
+ setobjs2s(L, ra + 3, ra); /* copy function */
+ L->top.p = ra + 3 + 3;
+ ProtectNT(luaD_call(L, ra + 3, GETARG_C(i))); /* do the call */
updatestack(ci); /* stack may have changed */
i = *(pc++); /* go to next instruction */
lua_assert(GET_OPCODE(i) == OP_TFORLOOP && ra == RA(i));
@@ -1834,10 +1846,8 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
vmcase(OP_TFORLOOP) {
l_tforloop: {
StkId ra = RA(i);
- if (!ttisnil(s2v(ra + 4))) { /* continue loop? */
- setobjs2s(L, ra + 2, ra + 4); /* save control variable */
+ if (!ttisnil(s2v(ra + 3))) /* continue loop? */
pc -= GETARG_Bx(i); /* jump back */
- }
vmbreak;
}}
vmcase(OP_SETLIST) {
diff --git a/testes/files.lua b/testes/files.lua
@@ -427,12 +427,12 @@ do -- testing closing file in line iteration
-- get the to-be-closed variable from a loop
local function gettoclose (lv)
lv = lv + 1
- local stvar = 0 -- to-be-closed is 4th state variable in the loop
+ local stvar = 0 -- to-be-closed is 3th state variable in the loop
for i = 1, 1000 do
local n, v = debug.getlocal(lv, i)
if n == "(for state)" then
stvar = stvar + 1
- if stvar == 4 then return v end
+ if stvar == 3 then return v end
end
end
end
