From 5ff408d2189c6c24fdf8908db4a31432bbdd6f15 Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Mon, 6 Jan 2020 11:38:31 -0300
Subject: Changed internal representation of booleans

Instead of an explicit value (field 'b'), true and false use different
tag variants. This avoids reading an extra field and results in more
direct code. (Most code that uses booleans needs to distinguish between
true and false anyway.)
---
 lvm.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

(limited to 'lvm.c')

diff --git a/lvm.c b/lvm.c
index 78c0ebe7..656def81 100644
--- a/lvm.c
+++ b/lvm.c
@@ -577,10 +577,9 @@ int luaV_equalobj (lua_State *L, const TValue *t1, const TValue *t2) {
   }
   /* values have same type and same variant */
   switch (ttypetag(t1)) {
-    case LUA_TNIL: return 1;
+    case LUA_TNIL: case LUA_TFALSE: case LUA_TTRUE: return 1;
     case LUA_TNUMINT: return (ivalue(t1) == ivalue(t2));
     case LUA_TNUMFLT: return luai_numeq(fltvalue(t1), fltvalue(t2));
-    case LUA_TBOOLEAN: return bvalue(t1) == bvalue(t2);  /* true must be 1! */
     case LUA_TLIGHTUSERDATA: return pvalue(t1) == pvalue(t2);
     case LUA_TLCF: return fvalue(t1) == fvalue(t2);
     case LUA_TSHRSTR: return eqshrstr(tsvalue(t1), tsvalue(t2));
@@ -1182,9 +1181,13 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         setobj2s(L, ra, rb);
         vmbreak;
       }
-      vmcase(OP_LOADBOOL) {
-        setbvalue(s2v(ra), GETARG_B(i));
-        if (GETARG_C(i)) pc++;  /* skip next instruction (if C) */
+      vmcase(OP_LOADFALSE) {
+        setbfvalue(s2v(ra));
+        if (GETARG_B(i)) pc++;  /* if B, skip next instruction */
+        vmbreak;
+      }
+      vmcase(OP_LOADTRUE) {
+        setbtvalue(s2v(ra));
         vmbreak;
       }
       vmcase(OP_LOADNIL) {
@@ -1503,8 +1506,10 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
       }
       vmcase(OP_NOT) {
         TValue *rb = vRB(i);
-        int nrb = l_isfalse(rb);  /* next assignment may change this value */
-        setbvalue(s2v(ra), nrb);
+        if (l_isfalse(rb))
+          setbtvalue(s2v(ra));
+        else
+          setbfvalue(s2v(ra));
         vmbreak;
       }
       vmcase(OP_LEN) {
-- 
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