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more direct implementation for tail calls.

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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47
ldo.c
View File

@ -1,5 +1,5 @@
/*
** $Id: ldo.c,v 2.171 2017/11/13 12:26:30 roberto Exp roberto $
** $Id: ldo.c,v 2.172 2017/11/13 15:36:52 roberto Exp roberto $
** Stack and Call structure of Lua
** See Copyright Notice in lua.h
*/
@ -280,14 +280,13 @@ void luaD_hook (lua_State *L, int event, int line) {
}
static void callhook (lua_State *L, CallInfo *ci) {
static void callhook (lua_State *L, CallInfo *ci, int istail) {
int hook;
ci->u.l.trap = 1;
if (!(L->hookmask & LUA_MASKCALL))
return; /* some other hook */
ci->u.l.savedpc++; /* hooks assume 'pc' is already incremented */
if (isLua(ci->previous) &&
GET_OPCODE(*(ci->previous->u.l.savedpc - 1)) == OP_TAILCALL) {
if (istail) {
ci->callstatus |= CIST_TAIL;
hook = LUA_HOOKTAILCALL;
}
@ -303,16 +302,18 @@ static void callhook (lua_State *L, CallInfo *ci) {
** it in stack below original 'func' so that 'luaD_precall' can call
** it. Raise an error if __call metafield is not a function.
*/
static void tryfuncTM (lua_State *L, StkId func) {
StkId luaD_tryfuncTM (lua_State *L, StkId func) {
const TValue *tm = luaT_gettmbyobj(L, s2v(func), TM_CALL);
StkId p;
if (!ttisfunction(tm))
luaG_typeerror(L, s2v(func), "call");
/* Open a hole inside the stack at 'func' */
checkstackp(L, 1, func); /* ensure space for metamethod */
for (p = L->top; p > func; p--)
setobjs2s(L, p, p-1);
L->top++; /* slot ensured by caller */
setobj2s(L, func, tm); /* tag method is the new function to be called */
L->top++;
setobj2s(L, func, tm); /* metamethod is the new function to be called */
return func;
}
@ -388,6 +389,33 @@ int luaD_poscall (lua_State *L, CallInfo *ci, StkId firstResult, int nres) {
#define next_ci(L) (L->ci = (L->ci->next ? L->ci->next : luaE_extendCI(L)))
/*
** Prepare a function for a tail call, building its call info on top
** of the current call info. 'n' is the number of arguments plus 1
** (so that it includes the function itself).
*/
void luaD_pretailcall (lua_State *L, CallInfo *ci, StkId func, int n) {
Proto *p = clLvalue(s2v(func))->p;
int fsize = p->maxstacksize; /* frame size */
int i;
for (i = 0; i < n; i++) /* move down function and arguments */
setobjs2s(L, ci->func + i, func + i);
checkstackp(L, fsize, func);
for (; i < p->numparams - p->is_vararg; i++)
setnilvalue(s2v(ci->func + i)); /* complete missing parameters */
if (p->is_vararg) {
L->top -= (func - ci->func); /* move down top */
luaT_adjustvarargs(L, p, n - 1);
}
L->top = ci->top = ci->func + 1 + fsize; /* top for new function */
lua_assert(ci->top <= L->stack_last);
ci->u.l.savedpc = p->code; /* starting point */
ci->callstatus |= CIST_TAIL;
if (L->hookmask)
callhook(L, ci, 1);
}
/*
** Prepares a function call: checks the stack, creates a new CallInfo
** entry, fills in the relevant information, calls hook if needed.
@ -440,12 +468,11 @@ int luaD_precall (lua_State *L, StkId func, int nresults) {
ci->u.l.savedpc = p->code; /* starting point */
ci->callstatus = CIST_LUA;
if (L->hookmask)
callhook(L, ci);
callhook(L, ci, 0);
return 0;
}
default: { /* not a function */
checkstackp(L, 1, func); /* ensure space for metamethod */
tryfuncTM(L, func); /* try to get '__call' metamethod */
func = luaD_tryfuncTM(L, func); /* try to get '__call' metamethod */
return luaD_precall(L, func, nresults); /* now it must be a function */
}
}

4
ldo.h
View File

@ -1,5 +1,5 @@
/*
** $Id: ldo.h,v 2.31 2017/06/29 15:06:44 roberto Exp $
** $Id: ldo.h,v 2.33 2017/11/07 13:25:26 roberto Exp roberto $
** Stack and Call structure of Lua
** See Copyright Notice in lua.h
*/
@ -48,8 +48,10 @@ LUAI_FUNC int luaD_protectedparser (lua_State *L, ZIO *z, const char *name,
const char *mode);
LUAI_FUNC void luaD_hook (lua_State *L, int event, int line);
LUAI_FUNC int luaD_precall (lua_State *L, StkId func, int nresults);
LUAI_FUNC void luaD_pretailcall (lua_State *L, CallInfo *ci, StkId func, int n);
LUAI_FUNC void luaD_call (lua_State *L, StkId func, int nResults);
LUAI_FUNC void luaD_callnoyield (lua_State *L, StkId func, int nResults);
LUAI_FUNC StkId luaD_tryfuncTM (lua_State *L, StkId func);
LUAI_FUNC int luaD_pcall (lua_State *L, Pfunc func, void *u,
ptrdiff_t oldtop, ptrdiff_t ef);
LUAI_FUNC int luaD_poscall (lua_State *L, CallInfo *ci, StkId firstResult,

42
lvm.c
View File

@ -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;