diff --git a/lcode.c b/lcode.c
index 3f0418b9..76702869 100644
--- a/lcode.c
+++ b/lcode.c
@@ -5,6 +5,8 @@
 */
 
 
+#define LUA_REENTRANT
+
 #include "lcode.h"
 #include "ldo.h"
 #include "llex.h"
@@ -47,9 +49,9 @@ int luaK_primitivecode (LexState *ls, Instruction i) {
 static void luaK_minus (LexState *ls) {
   Instruction *previous = previous_instruction(ls);
   switch(GET_OPCODE(*previous)) {
-    case PUSHINT: *previous = SETARG_S(*previous, -GETARG_S(*previous)); return;
-    case PUSHNUM: *previous = SET_OPCODE(*previous, PUSHNEGNUM); return;
-    case PUSHNEGNUM: *previous = SET_OPCODE(*previous, PUSHNUM); return;
+    case PUSHINT: SETARG_S(*previous, -GETARG_S(*previous)); return;
+    case PUSHNUM: SET_OPCODE(*previous, PUSHNEGNUM); return;
+    case PUSHNEGNUM: SET_OPCODE(*previous, PUSHNUM); return;
     default: luaK_primitivecode(ls, CREATE_0(MINUSOP));
   }
 }
@@ -59,7 +61,7 @@ static void luaK_gettable (LexState *ls) {
   Instruction *previous = previous_instruction(ls);
   luaK_deltastack(ls, -1);
   switch(GET_OPCODE(*previous)) {
-    case PUSHSTRING: *previous = SET_OPCODE(*previous, GETDOTTED); break;
+    case PUSHSTRING: SET_OPCODE(*previous, GETDOTTED); break;
     default: luaK_primitivecode(ls, CREATE_0(GETTABLE));
   }
 }
@@ -69,7 +71,7 @@ static void luaK_add (LexState *ls) {
   Instruction *previous = previous_instruction(ls);
   luaK_deltastack(ls, -1);
   switch(GET_OPCODE(*previous)) {
-    case PUSHINT: *previous = SET_OPCODE(*previous, ADDI); break;
+    case PUSHINT: SET_OPCODE(*previous, ADDI); break;
     default: luaK_primitivecode(ls, CREATE_0(ADDOP));
   }
 }
@@ -80,8 +82,8 @@ static void luaK_sub (LexState *ls) {
   luaK_deltastack(ls, -1);
   switch(GET_OPCODE(*previous)) {
     case PUSHINT:
-      *previous = SET_OPCODE(*previous, ADDI);
-      *previous = SETARG_S(*previous, -GETARG_S(*previous));
+      SET_OPCODE(*previous, ADDI);
+      SETARG_S(*previous, -GETARG_S(*previous));
       break;
     default: luaK_primitivecode(ls, CREATE_0(SUBOP));
   }
@@ -92,7 +94,7 @@ static void luaK_conc (LexState *ls) {
   Instruction *previous = previous_instruction(ls);
   luaK_deltastack(ls, -1);
   switch(GET_OPCODE(*previous)) {
-    case CONCOP: *previous = SETARG_U(*previous, GETARG_U(*previous)+1); break;
+    case CONCOP: SETARG_U(*previous, GETARG_U(*previous)+1); break;
     default: luaK_primitivecode(ls, CREATE_U(CONCOP, 2));
   }
 }
@@ -102,8 +104,8 @@ void luaK_retcode (LexState *ls, int nlocals, int nexps) {
   Instruction *previous = previous_instruction(ls);
   if (nexps > 0 && GET_OPCODE(*previous) == CALL) {
     LUA_ASSERT(ls->L, GETARG_B(*previous) == MULT_RET, "call should be open");
-    *previous = SET_OPCODE(*previous, TAILCALL);
-    *previous = SETARG_B(*previous, nlocals);
+    SET_OPCODE(*previous, TAILCALL);
+    SETARG_B(*previous, nlocals);
   }
   else
     luaK_primitivecode(ls, CREATE_U(RETCODE, nlocals));
@@ -115,7 +117,7 @@ static void luaK_pushnil (LexState *ls, int n) {
   luaK_deltastack(ls, n);
   switch(GET_OPCODE(*previous)) {
     case PUSHNIL:
-      *previous = SETARG_U(*previous, GETARG_U(*previous)+n);
+      SETARG_U(*previous, GETARG_U(*previous)+n);
       break;
     default: luaK_primitivecode(ls, CREATE_U(PUSHNIL, n));
   }
@@ -132,7 +134,7 @@ void luaK_fixjump (LexState *ls, int pc, int dest) {
   FuncState *fs = ls->fs;
   Instruction *jmp = &fs->f->code[pc];
   /* jump is relative to position following jump instruction */
-  *jmp = SETARG_S(*jmp, dest-(pc+1));
+  SETARG_S(*jmp, dest-(pc+1));
 }
 
 
@@ -213,7 +215,7 @@ void luaK_setcallreturns (LexState *ls, int nresults) {
   Instruction *i = previous_instruction(ls);
   if (GET_OPCODE(*i) == CALL) {  /* expression is a function call? */
     LUA_ASSERT(ls->L, GETARG_B(*i) == MULT_RET, "call should be open");
-    *i = SETARG_B(*i, nresults);  /* set nresults */
+    SETARG_B(*i, nresults);  /* set nresults */
     luaK_deltastack(ls, nresults);  /* push results */
   }
 }
@@ -224,41 +226,43 @@ static void assertglobal (LexState *ls, int index) {
 }
 
 
-void luaK_tostack (LexState *ls, expdesc *var) {
+static int discharge (LexState *ls, expdesc *var) {
   switch (var->k) {
     case VLOCAL:
-      luaK_U(ls, PUSHLOCAL, var->info, 1);
+      luaK_U(ls, PUSHLOCAL, var->u.index, 1);
       break;
     case VGLOBAL:
-      luaK_U(ls, GETGLOBAL, var->info, 1);
-      assertglobal(ls, var->info);  /* make sure that there is a global */
+      luaK_U(ls, GETGLOBAL, var->u.index, 1);
+      assertglobal(ls, var->u.index);  /* make sure that there is a global */
       break;
     case VINDEXED:
       luaK_gettable(ls);
       break;
     case VEXP:
-      return;  /* exp result is already on stack */
+      return 0;  /* nothing to do */
   }
   var->k = VEXP;
+  var->u.l.t = var->u.l.f = 0;
+  return 1;
 }
 
 
-void luaK_1tostack (LexState *ls, expdesc *var) {
-  if (var->k == VEXP)
+static void discharge1 (LexState *ls, expdesc *var) {
+  discharge(ls, var);
+ /* if it has jumps it is already discharged */
+  if (var->u.l.t == 0 && var->u.l.f  == 0)
     luaK_setcallreturns(ls, 1);  /* call must return 1 value */
-  else
-    luaK_tostack(ls, var);
 }
-
+  
 
 void luaK_storevar (LexState *ls, const expdesc *var) {
   switch (var->k) {
     case VLOCAL:
-      luaK_U(ls, SETLOCAL, var->info, -1);
+      luaK_U(ls, SETLOCAL, var->u.index, -1);
       break;
     case VGLOBAL:
-      luaK_U(ls, SETGLOBAL, var->info, -1);
-      assertglobal(ls, var->info);  /* make sure that there is a global */
+      luaK_U(ls, SETGLOBAL, var->u.index, -1);
+      assertglobal(ls, var->u.index);  /* make sure that there is a global */
       break;
     case VINDEXED:
       luaK_0(ls, SETTABLEPOP, -3);
@@ -269,40 +273,228 @@ void luaK_storevar (LexState *ls, const expdesc *var) {
 }
 
 
+static OpCode invertjump (OpCode op) {
+  switch (op) {
+    case IFNEQJMP: return IFEQJMP;
+    case IFEQJMP: return IFNEQJMP;
+    case IFLTJMP: return IFGEJMP;
+    case IFLEJMP: return IFGTJMP;
+    case IFGTJMP: return IFLEJMP;
+    case IFGEJMP: return IFLTJMP;
+    default:
+      LUA_INTERNALERROR(NULL, "invalid jump instruction");
+      return ENDCODE;  /* to avoid warnings */
+  }
+}
+
+
+static void insert_last (FuncState *fs, int *list) {
+  int temp = *list;
+  *list = fs->pc-1;
+  if (temp == 0)  /* chain list */
+    SETARG_S(fs->f->code[*list], 0);
+  else
+    SETARG_S(fs->f->code[*list], temp-fs->pc);
+}
+
+
+static void luaK_patchlistaux (LexState *ls, int list, int target,
+                               OpCode special, int special_target) {
+  if (list != 0) {
+    Instruction *code = ls->fs->f->code;
+    for (;;) {
+      Instruction *i = &code[list];
+      OpCode op = GET_OPCODE(*i);
+      int temp = GETARG_S(*i);
+      if (op == special)
+        SETARG_S(*i, special_target-(list+1));
+      else {
+        SETARG_S(*i, target-(list+1));
+        if (op == ONTJMP)
+          SET_OPCODE(*i, IFTJMP);
+        else if (op == ONFJMP)
+          SET_OPCODE(*i, IFFJMP);
+      }
+      if (temp == 0) return;
+      list += temp+1;
+    }
+  }
+}
+
+
+void luaK_patchlist (LexState *ls, int list, int target) {
+  luaK_patchlistaux(ls, list, target, ENDCODE, 0);
+}
+
+
+static int has_jumps (FuncState *fs, int list, OpCode ignore) {
+  if (list == 0) return 0;
+  else {
+    Instruction *code = fs->f->code;
+    for (;;) {
+      int temp = GETARG_S(code[list]);
+      if (GET_OPCODE(code[list]) != ignore) return 1;
+      else if (temp == 0) return 0;
+      list += temp+1;
+    }
+  }
+}
+
+
+static void concatlists (LexState *ls, int *l1, int l2) {
+  if (*l1 == 0)
+    *l1 = l2;
+  else if (l2 != 0) {
+    FuncState *fs = ls->fs;
+    int list = *l1;
+    for (;;) {  /* traverse `l1' */
+      int temp = GETARG_S(fs->f->code[list]);
+      if (temp == 0) {  /* end of list? */
+        SETARG_S(fs->f->code[list], l2-(list+1));  /* end points to `l2' */
+        return;
+      }
+      list += temp+1;
+    }
+  }
+}
+
+
+void luaK_goiftrue (LexState *ls, expdesc *v, int keepvalue) {
+  FuncState *fs = ls->fs;
+  Instruction *previous;
+  discharge1(ls, v);
+  previous = &fs->f->code[fs->pc-1];
+  if (ISJUMP(GET_OPCODE(*previous)))
+    SET_OPCODE(*previous, invertjump(GET_OPCODE(*previous)));
+  else {
+    OpCode jump = keepvalue ? ONFJMP : IFFJMP;
+    luaK_S(ls, jump, 0, -1);
+  }
+  insert_last(fs, &v->u.l.f);
+  luaK_patchlist(ls, v->u.l.t, luaK_getlabel(ls));
+  v->u.l.t = 0;
+}
+
+
+void luaK_goiffalse (LexState *ls, expdesc *v, int keepvalue) {
+  FuncState *fs = ls->fs;
+  Instruction *previous;
+  discharge1(ls, v);
+  previous = &fs->f->code[fs->pc-1];
+  if (!ISJUMP(GET_OPCODE(*previous))) {
+    OpCode jump = keepvalue ? ONTJMP : IFTJMP;
+    luaK_S(ls, jump, 0, -1);
+  }
+  insert_last(fs, &v->u.l.t);
+  luaK_patchlist(ls, v->u.l.f, luaK_getlabel(ls));
+  v->u.l.f = 0;
+}
+
+
+void luaK_tostack (LexState *ls, expdesc *v, int onlyone) {
+  if (discharge(ls, v)) return;
+  else {  /* is an expression */
+    FuncState *fs = ls->fs;
+    Instruction *previous = &fs->f->code[fs->pc-1];
+    if (!ISJUMP(GET_OPCODE(*previous)) && v->u.l.f == 0 && v->u.l.t == 0) {
+      /* it is an expression without jumps */
+      if (onlyone && v->k == VEXP)
+        luaK_setcallreturns(ls, 1);  /* call must return 1 value */
+      return;
+    }
+    else {  /* expression has jumps... */
+      int p_nil = 0;  /* position of an eventual PUSHNIL */
+      int p_1 = 0;  /* position of an eventual PUSHINT */
+      int final;  /* position after whole expression */
+      if (ISJUMP(GET_OPCODE(*previous))) {
+        insert_last(fs, &v->u.l.t);
+        p_nil = luaK_0(ls, PUSHNILJMP, 0);
+        p_1 = luaK_S(ls, PUSHINT, 1, 1);
+      }
+      else {  /* still may need a PUSHNIL or a PUSHINT */
+        int need_nil = has_jumps(fs, v->u.l.f, ONFJMP);  /* needs a PUSHNIL? */
+        int need_1 = has_jumps(fs, v->u.l.t, ONTJMP);  /* needs a PUSHINT? */
+        if (need_nil && need_1) {
+          luaK_S(ls, JMP, 2, 0);
+          p_nil = luaK_0(ls, PUSHNILJMP, 0);
+          p_1 = luaK_S(ls, PUSHINT, 1, 1);
+        }
+        else if (need_nil || need_1) {
+          luaK_S(ls, JMP, 1, 0);
+          if (need_nil)
+            p_nil = luaK_0(ls, PUSHNIL, 1);
+          else  /* need_1 */
+            p_1 = luaK_S(ls, PUSHINT, 1, 1);
+        }
+      }
+      final = luaK_getlabel(ls);
+      luaK_patchlistaux(ls, v->u.l.f, p_nil, ONFJMP, final);
+      luaK_patchlistaux(ls, v->u.l.t, p_1, ONTJMP, final);
+      v->u.l.f = v->u.l.t = 0;
+    }
+  }
+}
+
+
 void luaK_prefix (LexState *ls, int op, expdesc *v) {
-  luaK_1tostack(ls, v);
-  if (op == '-') luaK_minus(ls);
-  else luaK_0(ls, NOTOP, 0);
+  if (op == '-') {
+    luaK_tostack(ls, v, 1);
+    luaK_minus(ls);
+  }
+  else {  /* op == NOT */
+    FuncState *fs = ls->fs;
+    Instruction *previous;
+    discharge1(ls, v);
+    previous = &fs->f->code[fs->pc-1];
+    if (ISJUMP(GET_OPCODE(*previous)))
+      SET_OPCODE(*previous, invertjump(GET_OPCODE(*previous)));
+    else
+      luaK_0(ls, NOTOP, 0);
+    /* interchange true and false lists */
+    { int temp = v->u.l.f; v->u.l.f = v->u.l.t; v->u.l.t = temp; }
+  }
 }
 
 
 void luaK_infix (LexState *ls, int op, expdesc *v) {
-  luaK_1tostack(ls, v);
   if (op == AND)
-    v->info = luaK_0(ls, ONFJMP, -1);
+    luaK_goiftrue(ls, v, 1);
   else if (op == OR)
-    v->info = luaK_0(ls, ONTJMP, -1);
+    luaK_goiffalse(ls, v, 1);
+  else
+    luaK_tostack(ls, v, 1);
 } 
 
 
 void luaK_posfix (LexState *ls, int op, expdesc *v1, expdesc *v2) {
-  luaK_1tostack(ls, v2);
-  switch (op) {
-    case AND:  case OR:
-      luaK_fixjump(ls, v1->info, luaK_getlabel(ls));
-      break;
-    case '+': luaK_add(ls); break;
-    case '-': luaK_sub(ls); break;
-    case '*': luaK_0(ls, MULTOP, -1); break;
-    case '/': luaK_0(ls, DIVOP, -1); break;
-    case '^': luaK_0(ls, POWOP, -1); break;
-    case CONC: luaK_conc(ls); break;
-    case EQ: luaK_0(ls, EQOP, -1); break;
-    case NE: luaK_0(ls, NEQOP, -1); break;
-    case '>': luaK_0(ls, GTOP, -1); break;
-    case '<': luaK_0(ls, LTOP, -1); break;
-    case GE: luaK_0(ls, GEOP, -1); break;
-    case LE: luaK_0(ls, LEOP, -1); break;
+  if (op == AND) {
+    LUA_ASSERT(ls->L, v1->u.l.t == 0, "list must be closed");
+    discharge1(ls, v2);
+    v1->u.l.t = v2->u.l.t;
+    concatlists(ls, &v1->u.l.f, v2->u.l.f);
+  }
+  else if (op == OR) {
+    LUA_ASSERT(ls->L, v1->u.l.f == 0, "list must be closed");
+    discharge1(ls, v2);
+    v1->u.l.f = v2->u.l.f;
+    concatlists(ls, &v1->u.l.t, v2->u.l.t);
+  }
+  else {
+    luaK_tostack(ls, v2, 1);  /* `v2' must have a value */
+    switch (op) {
+      case '+': luaK_add(ls); break;
+      case '-': luaK_sub(ls); break;
+      case '*': luaK_0(ls, MULTOP, -1); break;
+      case '/': luaK_0(ls, DIVOP, -1); break;
+      case '^': luaK_0(ls, POWOP, -1); break;
+      case CONC: luaK_conc(ls); break;
+      case EQ: luaK_S(ls, IFEQJMP, 0, -2); break;
+      case NE: luaK_S(ls, IFNEQJMP, 0, -2); break;
+      case '>': luaK_S(ls, IFGTJMP, 0, -2); break;
+      case '<': luaK_S(ls, IFLTJMP, 0, -2); break;
+      case GE: luaK_S(ls, IFGEJMP, 0, -2); break;
+      case LE: luaK_S(ls, IFLEJMP, 0, -2); break;
+    }
   }
 }
 
diff --git a/lcode.h b/lcode.h
index 0f8eadc1..91674ad3 100644
--- a/lcode.h
+++ b/lcode.h
@@ -24,6 +24,9 @@ int luaK_primitivecode (LexState *ls, Instruction i);
 int luaK_code (LexState *ls, Instruction i, int delta);
 void luaK_retcode (LexState *ls, int nlocals, int nexps);
 void luaK_fixjump (LexState *ls, int pc, int dest);
+void luaK_patchlist (LexState *ls, int list, int target);
+void luaK_goiftrue (LexState *ls, expdesc *v, int keepvalue);
+void luaK_goiffalse (LexState *ls, expdesc *v, int keepvalue);
 int luaK_getlabel (LexState *ls);
 void luaK_deltastack (LexState *ls, int delta);
 void luaK_kstr (LexState *ls, int c);
@@ -31,8 +34,7 @@ void luaK_number (LexState *ls, real f);
 void luaK_adjuststack (LexState *ls, int n);
 int luaK_lastisopen (LexState *ls);
 void luaK_setcallreturns (LexState *ls, int nresults);
-void luaK_tostack (LexState *ls, expdesc *var);
-void luaK_1tostack (LexState *ls, expdesc *var);
+void luaK_tostack (LexState *ls, expdesc *v, int onlyone);
 void luaK_storevar (LexState *ls, const expdesc *var);
 void luaK_prefix (LexState *ls, int op, expdesc *v);
 void luaK_infix (LexState *ls, int op, expdesc *v);
diff --git a/lopcodes.h b/lopcodes.h
index 1e3b9ee9..cd19ff3d 100644
--- a/lopcodes.h
+++ b/lopcodes.h
@@ -11,7 +11,7 @@
 
 /*===========================================================================
   We assume that instructions are unsigned numbers with 4 bytes.
-  All instructions have an opcode in the lower byte. Moreover,
+  All instructions have an opcode in the 8 bits. Moreover,
   an instruction can have 0, 1, or 2 arguments. There are 4 types of
   Instructions:
   type 0: no arguments
@@ -24,21 +24,23 @@
   is the usigned value minus 2^23.
 ===========================================================================*/
 
+#define SIZE_INSTRUCTION	32
+
 #define SIZE_OP		8
-#define SIZE_U		24
-#define POS_U		8
-#define SIZE_S		24
-#define POS_S		8
-#define SIZE_A		16
-#define POS_A		16
+#define SIZE_U		(SIZE_INSTRUCTION-SIZE_OP)
+#define POS_U		SIZE_OP
+#define SIZE_S		(SIZE_INSTRUCTION-SIZE_OP)
+#define POS_S		SIZE_OP
 #define SIZE_B		8
-#define POS_B		8
+#define POS_B		SIZE_OP
+#define SIZE_A		(SIZE_INSTRUCTION-(SIZE_OP+SIZE_B))
+#define POS_A		(SIZE_OP+SIZE_B)
 
 #define EXCESS_S	(1<<(SIZE_S-1))		/* == 2^23 */
 
 
 /* creates a mask with `n' 1 bits at position `p' */
-#define MASK1(n,p)	((~((~0ul)<<n))<<p)
+#define MASK1(n,p)	((~((~(Instruction)0)<<n))<<p)
 
 /* creates a mask with `n' 0 bits at position `p' */
 #define MASK0(n,p)	(~MASK1(n,p))
@@ -58,11 +60,15 @@
 #define GETARG_A(i)	((int)((i)>>POS_A))
 #define GETARG_B(i)	((int)(((i)>>POS_B) & MASK1(SIZE_B,0)))
 
-#define SET_OPCODE(i,o)	(((i)&MASK0(SIZE_OP,0)) | (Instruction)(o))
-#define SETARG_U(i,u)	(((i)&MASK0(SIZE_U,POS_U)) | ((Instruction)(u)<<POS_U))
-#define SETARG_S(i,s)	(((i)&MASK0(SIZE_S,POS_S)) | ((Instruction)((s)+EXCESS_S)<<POS_S))
-#define SETARG_A(i,a)	(((i)&MASK0(SIZE_A,POS_A)) | ((Instruction)(a)<<POS_A))
-#define SETARG_B(i,b)	(((i)&MASK0(SIZE_B,POS_B)) | ((Instruction)(b)<<POS_B))
+#define SET_OPCODE(i,o)	((i) = (((i)&MASK0(SIZE_OP,0)) | (Instruction)(o)))
+#define SETARG_U(i,u)	((i) = (((i)&MASK0(SIZE_U,POS_U)) | \
+                               ((Instruction)(u)<<POS_U)))
+#define SETARG_S(i,s)	((i) = (((i)&MASK0(SIZE_S,POS_S)) | \
+                               ((Instruction)((s)+EXCESS_S)<<POS_S)))
+#define SETARG_A(i,a)	((i) = (((i)&MASK0(SIZE_A,POS_A)) | \
+                               ((Instruction)(a)<<POS_A)))
+#define SETARG_B(i,b)	((i) = (((i)&MASK0(SIZE_B,POS_B)) | \
+                               ((Instruction)(b)<<POS_B)))
 
 #define CREATE_0(o)	 ((Instruction)(o))
 #define CREATE_U(o,u)	 ((Instruction)(o) | (Instruction)(u)<<POS_U)
@@ -115,13 +121,6 @@ SETTABLE,/*	U	v a_u-a_1 i t	 a_u-a_1 i t	t[i]=v		*/
 SETLIST,/*	A B	v_b-v_0 t	t		t[i+a*FPF]=v_i	*/
 SETMAP,/*	U	v_u k_u - v_0 k_0 t	t	t[k_i]=v_i	*/
 
-NEQOP,/*	-	y x		(x~=y)? 1 : nil			*/
-EQOP,/*		-	y x		(x==y)? 1 : nil			*/
-LTOP,/*		-	y x		(x<y)? 1 : nil			*/
-LEOP,/*		-	y x		(x<y)? 1 : nil			*/
-GTOP,/*		-	y x		(x>y)? 1 : nil			*/
-GEOP,/*		-	y x		(x>=y)? 1 : nil			*/
-
 ADDOP,/*	-	y x		x+y				*/
 ADDI,/*		S	x		x+s				*/
 SUBOP,/*	-	y x		x-y				*/
@@ -132,19 +131,32 @@ CONCOP,/*	U	v_u-v_1		v1..-..v_u			*/
 MINUSOP,/*	-	x		-x				*/
 NOTOP,/*	-	x		(x==nil)? 1 : nil		*/
 
+IFNEQJMP,/*	J	y x		-		(x~=y)? PC+=s	*/
+IFEQJMP,/*	J	y x		-		(x==y)? PC+=s	*/
+IFLTJMP,/*	J	y x		-		(x<y)? PC+=s	*/
+IFLEJMP,/*	J	y x		-		(x<y)? PC+=s	*/
+IFGTJMP,/*	J	y x		-		(x>y)? PC+=s	*/
+IFGEJMP,/*	J	y x		-		(x>=y)? PC+=s	*/
+
+IFTJMP,/*	J	x		-		(x!=nil)? PC+=s	*/
+IFFJMP,/*	J	x		-		(x==nil)? PC+=s	*/
 ONTJMP,/*	J	x		(x!=nil)? x : -	(x!=nil)? PC+=s	*/
 ONFJMP,/*	J	x		(x==nil)? x : -	(x==nil)? PC+=s	*/
 JMP,/*		J	-		-		PC+=s		*/
-IFTJMP,/*	J	x		-		(x!=nil)? PC+=s	*/
-IFFJMP,/*	J	x		-		(x==nil)? PC+=s	*/
 
-CLOSURE,/*	A B	v_b-v_1		closure(CNST[a], v_b-v_1)	*/
+PUSHNILJMP,/*	-	-		nil		PC++;		*/
+
+CLOSURE,/*	A B	v_b-v_1		closure(CNST[a], v_1-v_b)	*/
 
 SETLINE/*	U	-		-		LINE=u		*/
 
 } OpCode;
 
 
+
+#define ISJUMP(o)	(IFNEQJMP <= (o) && (o) <= JMP)
+
+
 #define RFIELDS_PER_FLUSH 32	/* records (SETMAP) */
 #define LFIELDS_PER_FLUSH 64    /* FPF - lists (SETLIST) (<=MAXARG_B) */
 
diff --git a/lparser.c b/lparser.c
index 7fb5a0d7..a8198190 100644
--- a/lparser.c
+++ b/lparser.c
@@ -218,7 +218,7 @@ static void singlevar (LexState *ls, TaggedString *n, expdesc *var, int prev) {
   int i = aux_localname(fs, n);
   if (i >= 0) {  /* local value? */
     var->k = VLOCAL;
-    var->info = i;
+    var->u.index = i;
   }
   else {
     FuncState *level = fs;
@@ -226,7 +226,7 @@ static void singlevar (LexState *ls, TaggedString *n, expdesc *var, int prev) {
       if (aux_localname(level, n) >= 0)
         luaX_syntaxerror(ls, "cannot access a variable in outer scope", n->str);
     var->k = VGLOBAL;
-    var->info = string_constant(ls, fs, n);
+    var->u.index = string_constant(ls, fs, n);
   }
 }
 
@@ -237,7 +237,7 @@ static int indexupvalue (LexState *ls, TaggedString *n) {
   int i;
   singlevar(ls, n, &v, 1);
   for (i=0; i<fs->nupvalues; i++) {
-    if (fs->upvalues[i].k == v.k && fs->upvalues[i].info == v.info)
+    if (fs->upvalues[i].k == v.k && fs->upvalues[i].u.index == v.u.index)
       return i;
   }
   /* new one */
@@ -296,9 +296,9 @@ static void code_args (LexState *ls, int nparams, int dots) {
 static int getvarname (LexState *ls, expdesc *var) {
   switch (var->k) {
     case VGLOBAL:
-      return var->info;
+      return var->u.index;
     case VLOCAL:
-      return string_constant(ls, ls->fs, ls->fs->localvar[var->info]);
+      return string_constant(ls, ls->fs, ls->fs->localvar[var->u.index]);
       break;
     default:
       error_unexpected(ls);  /* there is no `var name' */
@@ -311,7 +311,7 @@ static void func_onstack (LexState *ls, FuncState *func) {
   TProtoFunc *f = ls->fs->f;
   int i;
   for (i=0; i<func->nupvalues; i++)
-    luaK_1tostack(ls, &func->upvalues[i]);
+    luaK_tostack(ls, &func->upvalues[i], 1);
   luaM_growvector(ls->L, f->kproto, f->nkproto, 1, TProtoFunc *,
                   constantEM, MAXARG_A);
   f->kproto[f->nkproto++] = func->f;
@@ -388,12 +388,12 @@ static int explist1 (LexState *ls) {
   expdesc v;
   expr(ls, &v);
   while (ls->token == ',') {
-    luaK_1tostack(ls, &v);  /* gets only 1 value from previous expression */
+    luaK_tostack(ls, &v, 1);  /* gets only 1 value from previous expression */
     next(ls);  /* skip comma */
     expr(ls, &v);
     n++;
   }
-  luaK_tostack(ls, &v);
+  luaK_tostack(ls, &v, 0);
   return n;
 }
 
@@ -451,14 +451,14 @@ static void var_or_func_tail (LexState *ls, expdesc *v) {
     switch (ls->token) {
       case '.':  /* var_or_func_tail -> '.' NAME */
         next(ls);
-        luaK_1tostack(ls, v);  /* `v' must be on stack */
+        luaK_tostack(ls, v, 1);  /* `v' must be on stack */
         luaK_kstr(ls, checkname(ls));
         v->k = VINDEXED;
         break;
 
       case '[':  /* var_or_func_tail -> '[' exp1 ']' */
         next(ls);
-        luaK_1tostack(ls, v);  /* `v' must be on stack */
+        luaK_tostack(ls, v, 1);  /* `v' must be on stack */
         v->k = VINDEXED;
         exp1(ls);
         check(ls, ']');
@@ -468,17 +468,19 @@ static void var_or_func_tail (LexState *ls, expdesc *v) {
         int name;
         next(ls);
         name = checkname(ls);
-        luaK_1tostack(ls, v);  /* `v' must be on stack */
+        luaK_tostack(ls, v, 1);  /* `v' must be on stack */
         luaK_U(ls, PUSHSELF, name, 1);
         funcargs(ls, 1);
         v->k = VEXP;
+        v->u.l.t = v->u.l.f = 0;
         break;
       }
 
       case '(': case STRING: case '{':  /* var_or_func_tail -> funcargs */
-        luaK_1tostack(ls, v);  /* `v' must be on stack */
+        luaK_tostack(ls, v, 1);  /* `v' must be on stack */
         funcargs(ls, 0);
         v->k = VEXP;
+        v->u.l.t = v->u.l.f = 0;
         break;
 
       default: return;  /* should be follow... */
@@ -492,6 +494,7 @@ static void var_or_func (LexState *ls, expdesc *v) {
   if (optional(ls, '%')) {  /* upvalue? */
     pushupvalue(ls, str_checkname(ls));
     v->k = VEXP;
+    v->u.l.t = v->u.l.f = 0;
   }
   else  /* variable name */
     singlevar(ls, str_checkname(ls), v, 0);
@@ -591,7 +594,7 @@ static void constructor_part (LexState *ls, constdesc *cd) {
         cd->k = 1;  /* record */
       }
       else {
-        luaK_tostack(ls, &v);
+        luaK_tostack(ls, &v, 0);
         cd->n = listfields(ls);
         cd->k = 0;  /* list */
       }
@@ -632,7 +635,7 @@ static void constructor (LexState *ls) {
   }
   check_match(ls, '}', '{', line);
   /* set initial table size */
-  ls->fs->f->code[pc] = SETARG_U(ls->fs->f->code[pc], nelems);
+  SETARG_U(ls->fs->f->code[pc], nelems);
 }
 
 /* }====================================================================== */
@@ -691,13 +694,14 @@ static void simpleexp (LexState *ls, expdesc *v) {
       return;
   }
   v->k = VEXP;
+  v->u.l.t = v->u.l.f = 0;
 }
 
 
 static void exp1 (LexState *ls) {
   expdesc v;
   expr(ls, &v);
-  luaK_1tostack(ls, &v);
+  luaK_tostack(ls, &v, 1);
 }
 
 
@@ -820,10 +824,13 @@ static void whilestat (LexState *ls, int line) {
   FuncState *fs = ls->fs;
   int while_init = luaK_getlabel(ls);
   int loopentry;  /* point to jump to repeat the loop */
+  int cond_init;  /* init of condition, after the move */
   int cond_size;
+  expdesc v;
   int i;
   next(ls);  /* skip WHILE */
-  exp1(ls);  /* read condition */
+  expr(ls, &v);  /* read condition */
+  luaK_goiffalse(ls, &v, 0);
   cond_size = fs->pc - while_init;
   /* save condition (to move it to after body) */
   if (cond_size > MAX_WHILE_EXP)
@@ -831,28 +838,31 @@ static void whilestat (LexState *ls, int line) {
   for (i=0; i<cond_size; i++) buffer[i] = fs->f->code[while_init+i];
   /* go back to state prior condition */
   fs->pc = while_init;
-  luaK_deltastack(ls, -1);
   luaK_S(ls, JMP, 0, 0);  /* initial jump to condition */
   check(ls, DO);
   loopentry = luaK_getlabel(ls);
   block(ls);
   check_match(ls, END, WHILE, line);
-  luaK_fixjump(ls, while_init, luaK_getlabel(ls));
-  /* copy condition to new position, and correct stack */
+  cond_init = luaK_getlabel(ls);
+  luaK_fixjump(ls, while_init, cond_init);
+  /* correct `v' and  copy condition to new position */
+  if (v.u.l.t != 0) v.u.l.t += cond_init-while_init;
   for (i=0; i<cond_size; i++) luaK_primitivecode(ls, buffer[i]);
-  luaK_deltastack(ls, 1);
-  luaK_fixjump(ls, luaK_S(ls, IFTJMP, 0, -1), loopentry);
+  luaK_patchlist(ls, v.u.l.t, loopentry);
+  luaK_getlabel(ls);  /* mark possible jump to this point */
 }
 
 
 static void repeatstat (LexState *ls, int line) {
   /* repeatstat -> REPEAT block UNTIL exp1 */
   int repeat_init = luaK_getlabel(ls);
+  expdesc v;
   next(ls);
   block(ls);
   check_match(ls, UNTIL, REPEAT, line);
-  exp1(ls);
-  luaK_fixjump(ls, luaK_S(ls, IFFJMP, 0, -1), repeat_init);
+  expr(ls, &v);
+  luaK_goiftrue(ls, &v, 0);
+  luaK_patchlist(ls, v.u.l.f, repeat_init);
 }
 
 
@@ -900,7 +910,7 @@ static int funcname (LexState *ls, expdesc *v) {
   if (ls->token == ':' || ls->token == '.') {
     needself = (ls->token == ':');
     next(ls);
-    luaK_1tostack(ls, v);
+    luaK_tostack(ls, v, 1);
     luaK_kstr(ls, checkname(ls));
     v->k = VINDEXED;
   }
@@ -943,11 +953,11 @@ static void namestat (LexState *ls) {
 static void ifpart (LexState *ls, int line) {
   /* ifpart -> cond THEN block (ELSEIF ifpart | [ELSE block] END) */
   FuncState *fs = ls->fs;
-  int c;  /* address of the conditional jump */
+  expdesc v;
   int elseinit;
   next(ls);  /* skip IF or ELSEIF */
-  exp1(ls);  /* cond */
-  c = luaK_S(ls, IFFJMP, 0, -1);  /* 1st jump: over `then' part */
+  expr(ls, &v);  /* cond */
+  luaK_goiftrue(ls, &v, 0);
   check(ls, THEN);
   block(ls);  /* `then' part */
   luaK_S(ls, JMP, 0, 0);  /* 2nd jump: over `else' part */
@@ -960,13 +970,13 @@ static void ifpart (LexState *ls, int line) {
     check_match(ls, END, IF, line);
   }
   if (fs->pc > elseinit) {  /* is there an `else' part? */
-    luaK_fixjump(ls, c, elseinit);  /* fix 1st jump to `else' part */
     luaK_fixjump(ls, elseinit-1, luaK_getlabel(ls));  /* fix 2nd jump */
   }
   else {  /* no else part */
     fs->pc--;  /* remove 2nd jump */
-    luaK_fixjump(ls, c, luaK_getlabel(ls));  /* fix 1st jump to `if' end */
+    elseinit = luaK_getlabel(ls);  /* `elseinit' points to end */
   }
+  luaK_patchlist(ls, v.u.l.f, elseinit);  /* fix 1st jump to `else' part */
 }
 
 
diff --git a/lparser.h b/lparser.h
index adc7f012..01332478 100644
--- a/lparser.h
+++ b/lparser.h
@@ -47,15 +47,21 @@
 */
 
 typedef enum {
-  VGLOBAL,  /* info is constant index of global name */
-  VLOCAL,   /* info is stack index */
+  VGLOBAL,
+  VLOCAL,
   VINDEXED,
-  VEXP      /* info is jump target if exp has internal jumps */
+  VEXP
 } expkind;
 
 typedef struct expdesc {
   expkind k;
-  int info;
+  union {
+    int index;  /* VGLOBAL: `kstr' index of global name; VLOCAL: stack index */
+    struct {
+      int t;  /* patch list of `exit when true' */
+      int f;  /* patch list of `exit when false' */
+    } l;
+  } u;
 } expdesc;
 
 
diff --git a/lvm.c b/lvm.c
index 4a24c43a..5fa8e1c6 100644
--- a/lvm.c
+++ b/lvm.c
@@ -478,36 +478,6 @@ StkId luaV_execute (lua_State *L, const Closure *cl, const TProtoFunc *tf,
         break;
       }
 
-      case NEQOP:
-        top--;
-        setbool(top-1, !luaO_equalObj(top-1, top));
-        break;
-
-      case EQOP:
-        top--;
-        setbool(top-1, luaO_equalObj(top-1, top));
-        break;
-
-      case LTOP:
-        top--;
-        setbool(top-1, luaV_lessthan(L, top-1, top, top+1));
-        break;
-
-      case LEOP:  /* a <= b  ===  !(b<a) */
-        top--;
-        setbool(top-1, !luaV_lessthan(L, top, top-1, top+1));
-        break;
-
-      case GTOP:  /* a > b  ===  (b<a) */
-        top--;
-        setbool(top-1, luaV_lessthan(L, top, top-1, top+1));
-        break;
-
-      case GEOP:  /* a >= b  ===  !(a<b) */
-        top--;
-        setbool(top-1, !luaV_lessthan(L, top-1, top, top+1));
-        break;
-
       case ADDOP:
         if (tonumber(top-1) || tonumber(top-2))
           call_arith(L, top, IM_ADD);
@@ -579,6 +549,44 @@ StkId luaV_execute (lua_State *L, const Closure *cl, const TProtoFunc *tf,
         nvalue(top-1) = 1;
         break;
 
+      case IFNEQJMP:
+        top -= 2;
+        if (!luaO_equalObj(top, top+1)) pc += GETARG_S(i);
+        break;
+
+      case IFEQJMP:
+        top -= 2;
+        if (luaO_equalObj(top, top+1)) pc += GETARG_S(i);
+        break;
+
+      case IFLTJMP:
+        top -= 2;
+        if (luaV_lessthan(L, top, top+1, top+2)) pc += GETARG_S(i);
+        break;
+
+      case IFLEJMP:  /* a <= b  ===  !(b<a) */
+        top -= 2;
+        if (!luaV_lessthan(L, top+1, top, top+2)) pc += GETARG_S(i);
+        break;
+
+      case IFGTJMP:  /* a > b  ===  (b<a) */
+        top -= 2;
+        if (luaV_lessthan(L, top+1, top, top+2)) pc += GETARG_S(i);
+        break;
+
+      case IFGEJMP:  /* a >= b  ===  !(a<b) */
+        top -= 2;
+        if (!luaV_lessthan(L, top, top+1, top+2)) pc += GETARG_S(i);
+        break;
+
+      case IFTJMP:
+        if (ttype(--top) != LUA_T_NIL) pc += GETARG_S(i);
+        break;
+
+      case IFFJMP:
+        if (ttype(--top) == LUA_T_NIL) pc += GETARG_S(i);
+        break;
+
       case ONTJMP:
         if (ttype(top-1) != LUA_T_NIL) pc += GETARG_S(i);
         else top--;
@@ -593,12 +601,9 @@ StkId luaV_execute (lua_State *L, const Closure *cl, const TProtoFunc *tf,
         pc += GETARG_S(i);
         break;
 
-      case IFTJMP:
-        if (ttype(--top) != LUA_T_NIL) pc += GETARG_S(i);
-        break;
-
-      case IFFJMP:
-        if (ttype(--top) == LUA_T_NIL) pc += GETARG_S(i);
+      case PUSHNILJMP:
+        ttype(top++) = LUA_T_NIL;
+        pc++;
         break;
 
       case CLOSURE: