From 901d76009346d76996679c02deee708bf225e91e Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Fri, 11 Jun 2021 13:41:07 -0300
Subject: Simpler implementation for tail calls

Tail calls handled by 'luaD_precall', like regular calls, to avoid
code duplication.
---
 lvm.c | 20 +++++++-------------
 1 file changed, 7 insertions(+), 13 deletions(-)

(limited to 'lvm.c')

diff --git a/lvm.c b/lvm.c
index e4b1903e..485b9caa 100644
--- a/lvm.c
+++ b/lvm.c
@@ -1632,11 +1632,11 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
           L->top = ra + b;  /* top signals number of arguments */
         /* else previous instruction set top */
         savepc(L);  /* in case of errors */
-        if ((newci = luaD_precall(L, ra, nresults)) == NULL)
+        if ((newci = luaD_precall(L, ra, nresults, 0)) == NULL)
           updatetrap(ci);  /* C call; nothing else to be done */
         else {  /* Lua call: run function in this same C frame */
           ci = newci;
-          ci->callstatus = 0;  /* call re-uses 'luaV_execute' */
+          ci->callstatus = 0;
           goto startfunc;
         }
         vmbreak;
@@ -1648,21 +1648,18 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         int delta = (nparams1) ? ci->u.l.nextraargs + nparams1 : 0;
         if (b != 0)
           L->top = ra + b;
-        else  /* previous instruction set top */
-          b = cast_int(L->top - ra);
+        /* else previous instruction set top */
         savepc(ci);  /* several calls here can raise errors */
         if (TESTARG_k(i)) {
           luaF_closeupval(L, base);  /* close upvalues from current call */
           lua_assert(L->tbclist < base);  /* no pending tbc variables */
           lua_assert(base == ci->func + 1);
         }
-        while (!ttisfunction(s2v(ra))) {  /* not a function? */
-          luaD_tryfuncTM(L, ra);  /* try '__call' metamethod */
-          b++;  /* there is now one extra argument */
-          checkstackGCp(L, 1, ra);
+        if (luaD_precall(L, ra, LUA_MULTRET, delta + 1)) {  /* Lua function? */
+          ci->callstatus |= CIST_TAIL;
+          goto startfunc;  /* execute the callee */
         }
-        if (!ttisLclosure(s2v(ra))) {  /* C function? */
-          luaD_precall(L, ra, LUA_MULTRET);  /* call it */
+        else {  /* C function */
           updatetrap(ci);
           updatestack(ci);  /* stack may have been relocated */
           ci->func -= delta;  /* restore 'func' (if vararg) */
@@ -1670,9 +1667,6 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
           updatetrap(ci);  /* 'luaD_poscall' can change hooks */
           goto ret;  /* caller returns after the tail call */
         }
-        ci->func -= delta;  /* restore 'func' (if vararg) */
-        luaD_pretailcall(L, ci, ra, b);  /* prepare call frame */
-        goto startfunc;  /* execute the callee */
       }
       vmcase(OP_RETURN) {
         int n = GETARG_B(i) - 1;  /* number of results */
-- 
cgit v1.2.3-55-g6feb