From 0593256707ceddb1bc9cd4b25b822a7fbcfedd66 Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Thu, 21 Mar 2024 11:23:21 -0300
Subject: 'luaH_get' functions return tag of the result

Undoing previous commit. Returning TValue increases code size without
any visible gains. Returning the tag is a little simpler than returning
a special code (HOK/HNOTFOUND) and the tag is useful by itself in
some cases.
---
 lvm.c | 61 ++++++++++++++++++++++++++++++-------------------------------
 1 file changed, 30 insertions(+), 31 deletions(-)

(limited to 'lvm.c')

diff --git a/lvm.c b/lvm.c
index a251f423..cfa9961b 100644
--- a/lvm.c
+++ b/lvm.c
@@ -285,13 +285,12 @@ static int floatforloop (StkId ra) {
 
 
 /*
-** Finish the table access 'val = t[key]'.
+** Finish the table access 'val = t[key]' and return the tag of the result.
 */
-void luaV_finishget_ (lua_State *L, const TValue *t, TValue *key, StkId val,
-                       int tag) {
+int luaV_finishget (lua_State *L, const TValue *t, TValue *key, StkId val,
+                      int tag) {
   int loop;  /* counter to avoid infinite loops */
   const TValue *tm;  /* metamethod */
-  TValue aux;
   for (loop = 0; loop < MAXTAGLOOP; loop++) {
     if (tag == LUA_VNOTABLE) {  /* 't' is not a table? */
       lua_assert(!ttistable(t));
@@ -304,22 +303,22 @@ void luaV_finishget_ (lua_State *L, const TValue *t, TValue *key, StkId val,
       tm = fasttm(L, hvalue(t)->metatable, TM_INDEX);  /* table's metamethod */
       if (tm == NULL) {  /* no metamethod? */
         setnilvalue(s2v(val));  /* result is nil */
-        return;
+        return LUA_VNIL;
       }
       /* else will try the metamethod */
     }
     if (ttisfunction(tm)) {  /* is metamethod a function? */
       luaT_callTMres(L, tm, t, key, val);  /* call it */
-      return;
+      return ttypetag(s2v(val));
     }
     t = tm;  /* else try to access 'tm[key]' */
-    luaV_fastget(t, key, s2v(val), luaH_get, aux);
-    if (!isemptyV(aux))
-      return;  /* done */
+    luaV_fastget(t, key, s2v(val), luaH_get, tag);
+    if (!tagisempty(tag))
+      return tag;  /* done */
     /* else repeat (tail call 'luaV_finishget') */
-    tag = ttypetagV(aux);
   }
   luaG_runerror(L, "'__index' chain too long; possible loop");
+  return 0;  /* to avoid warnings */
 }
 
 
@@ -1247,36 +1246,36 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         TValue *upval = cl->upvals[GETARG_B(i)]->v.p;
         TValue *rc = KC(i);
         TString *key = tsvalue(rc);  /* key must be a short string */
-        TValue aux;
-        luaV_fastget(upval, key, s2v(ra), luaH_getshortstr, aux);
-        if (isemptyV(aux))
-          Protect(luaV_finishget(L, upval, rc, ra, aux));
+        int tag;
+        luaV_fastget(upval, key, s2v(ra), luaH_getshortstr, tag);
+        if (tagisempty(tag))
+          Protect(luaV_finishget(L, upval, rc, ra, tag));
         vmbreak;
       }
       vmcase(OP_GETTABLE) {
         StkId ra = RA(i);
         TValue *rb = vRB(i);
         TValue *rc = vRC(i);
-        TValue aux;
+        int tag;
         if (ttisinteger(rc)) {  /* fast track for integers? */
-          luaV_fastgeti(rb, ivalue(rc), s2v(ra), aux);
+          luaV_fastgeti(rb, ivalue(rc), s2v(ra), tag);
         }
         else
-          luaV_fastget(rb, rc, s2v(ra), luaH_get, aux);
-        if (isemptyV(aux))  /* fast track for integers? */
-          Protect(luaV_finishget(L, rb, rc, ra, aux));
+          luaV_fastget(rb, rc, s2v(ra), luaH_get, tag);
+        if (tagisempty(tag))
+          Protect(luaV_finishget(L, rb, rc, ra, tag));
         vmbreak;
       }
       vmcase(OP_GETI) {
         StkId ra = RA(i);
         TValue *rb = vRB(i);
         int c = GETARG_C(i);
-        TValue aux;
-        luaV_fastgeti(rb, c, s2v(ra), aux);
-        if (isemptyV(aux)) {
+        int tag;
+        luaV_fastgeti(rb, c, s2v(ra), tag);
+        if (tagisempty(tag)) {
           TValue key;
           setivalue(&key, c);
-          Protect(luaV_finishget(L, rb, &key, ra, aux));
+          Protect(luaV_finishget(L, rb, &key, ra, tag));
         }
         vmbreak;
       }
@@ -1285,10 +1284,10 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         TValue *rb = vRB(i);
         TValue *rc = KC(i);
         TString *key = tsvalue(rc);  /* key must be a short string */
-        TValue aux;
-        luaV_fastget(rb, key, s2v(ra), luaH_getshortstr, aux);
-        if (isemptyV(aux))
-          Protect(luaV_finishget(L, rb, rc, ra, aux));
+        int tag;
+        luaV_fastget(rb, key, s2v(ra), luaH_getshortstr, tag);
+        if (tagisempty(tag))
+          Protect(luaV_finishget(L, rb, rc, ra, tag));
         vmbreak;
       }
       vmcase(OP_SETTABUP) {
@@ -1370,14 +1369,14 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
       }
       vmcase(OP_SELF) {
         StkId ra = RA(i);
-        TValue aux;
+        int tag;
         TValue *rb = vRB(i);
         TValue *rc = RKC(i);
         TString *key = tsvalue(rc);  /* key must be a string */
         setobj2s(L, ra + 1, rb);
-        luaV_fastget(rb, key, s2v(ra), luaH_getstr, aux);
-        if (isemptyV(aux))
-          Protect(luaV_finishget(L, rb, rc, ra, aux));
+        luaV_fastget(rb, key, s2v(ra), luaH_getstr, tag);
+        if (tagisempty(tag))
+          Protect(luaV_finishget(L, rb, rc, ra, tag));
         vmbreak;
       }
       vmcase(OP_ADDI) {
-- 
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