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more direct implementation for tail calls.

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This commit is contained in:
Roberto Ierusalimschy
2017-11-21 12:18:03 -02:00
parent f3ca52bfa9
commit 14c3aa12b5
3 changed files with 57 additions and 36 deletions
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42
lvm.c
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@@ -1,5 +1,5 @@
/*
** $Id: lvm.c,v 2.311 2017/11/16 12:59:14 roberto Exp roberto $
** $Id: lvm.c,v 2.312 2017/11/20 12:57:39 roberto Exp roberto $
** Lua virtual machine
** See Copyright Notice in lua.h
*/
@@ -1429,31 +1429,23 @@ void luaV_execute (lua_State *L) {
vmbreak;
}
vmcase(OP_TAILCALL) {
int b = GETARG_B(i);
if (b != 0) L->top = ra+b; /* else previous instruction set top */
int b = GETARG_B(i); /* number of arguments + 1 (function) */
if (b != 0)
L->top = ra + b;
else /* previous instruction set top */
b = L->top - ra;
lua_assert(GETARG_C(i) - 1 == LUA_MULTRET);
savepc(L);
if (luaD_precall(L, ra, LUA_MULTRET)) /* C function? */
updatetrap(ci);
else {
/* tail call: put called frame (n) in place of caller one (o) */
CallInfo *nci = L->ci; /* called frame (new) */
CallInfo *oci = nci->previous; /* caller frame (old) */
StkId nfunc = nci->func; /* called function */
StkId ofunc = oci->func; /* caller function */
/* last stack slot filled by 'precall' */
StkId lim = nfunc + 1 + getproto(s2v(nfunc))->numparams;
int aux;
/* close all upvalues from previous call */
if (cl->p->sizep > 0) luaF_close(L, ofunc + 1);
/* move new frame into old one */
for (aux = 0; nfunc + aux < lim; aux++)
setobjs2s(L, ofunc + aux, nfunc + aux);
oci->top = L->top = ofunc + (L->top - nfunc); /* correct top */
oci->u.l.savedpc = nci->u.l.savedpc;
oci->callstatus |= CIST_TAIL; /* function was tail called */
ci = L->ci = oci; /* remove new frame */
lua_assert(L->top == ofunc + 1 + getproto(s2v(ofunc))->maxstacksize);
if (!ttisfunction(s2v(ra))) { /* not a function? */
/* try to get '__call' metamethod */
Protect(ra = luaD_tryfuncTM(L, ra));
b++; /* there is now one extra argument */
}
if (!ttisLclosure(s2v(ra))) /* C function? */
Protect(luaD_precall(L, ra, LUA_MULTRET)); /* call it */
else { /* tail call */
if (cl->p->sizep > 0) /* close upvalues from previous call */
luaF_close(L, ci->func + 1);
luaD_pretailcall(L, ci, ra, b); /* prepare call frame */
goto newframe; /* restart luaV_execute over new Lua function */
}
vmbreak;