Micro optimization in OP_RETURN and OP_TAILCALL
Many functions are vararg but create no upvalues, so it is better
to separate the tests for these two kinds of "extra work".
diff --git a/lcode.c b/lcode.c
index a0d7757..e57ad28 100644
--- a/lcode.c
+++ b/lcode.c
@@ -1745,10 +1745,10 @@
SET_OPCODE(*pc, OP_RETURN);
} /* FALLTHROUGH */
case OP_RETURN: case OP_TAILCALL: {
- if (fs->needclose || p->is_vararg) {
- SETARG_C(*pc, p->is_vararg ? p->numparams + 1 : 0);
- SETARG_k(*pc, 1); /* signal that there is extra work */
- }
+ if (fs->needclose)
+ SETARG_k(*pc, 1); /* signal that it needs to close */
+ if (p->is_vararg)
+ SETARG_C(*pc, p->numparams + 1); /* signal that it is vararg */
break;
}
case OP_JMP: {
diff --git a/lopcodes.h b/lopcodes.h
index 371cb3a..26b1850 100644
--- a/lopcodes.h
+++ b/lopcodes.h
@@ -338,10 +338,9 @@
(*) All 'skips' (pc++) assume that next instruction is a jump.
(*) In instructions OP_RETURN/OP_TAILCALL, 'k' specifies that the
- function either builds upvalues, which may need to be closed, or is
- vararg, which must be corrected before returning. When 'k' is true,
- C > 0 means the function is vararg and (C - 1) is its number of
- fixed parameters.
+ function builds upvalues, which may need to be closed. C > 0 means
+ the function is vararg, so that its 'func' must be corrected before
+ returning; in this case, (C - 1) is its number of fixed parameters.
(*) In comparisons with an immediate operand, C signals whether the
original operand was a float.
diff --git a/lvm.c b/lvm.c
index 9838500..7e6f148 100644
--- a/lvm.c
+++ b/lvm.c
@@ -1564,16 +1564,15 @@
}
vmcase(OP_TAILCALL) {
int b = GETARG_B(i); /* number of arguments + 1 (function) */
- int delta = 0; /* virtual 'func' - real 'func' (vararg functions) */
+ int nparams1 = GETARG_C(i);
+ /* delat is virtual 'func' - real 'func' (vararg functions) */
+ 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);
savepc(ci); /* some calls here can raise errors */
if (TESTARG_k(i)) {
- int nparams1 = GETARG_C(i);
- if (nparams1) /* vararg function? */
- delta = ci->u.l.nextraargs + nparams1;
/* close upvalues from current call; the compiler ensures
that there are no to-be-closed variables here */
luaF_close(L, base, NOCLOSINGMETH);
@@ -1599,18 +1598,18 @@
}
vmcase(OP_RETURN) {
int n = GETARG_B(i) - 1; /* number of results */
+ int nparams1 = GETARG_C(i);
if (n < 0) /* not fixed? */
n = cast_int(L->top - ra); /* get what is available */
savepc(ci);
if (TESTARG_k(i)) {
- int nparams1 = GETARG_C(i);
if (L->top < ci->top)
L->top = ci->top;
luaF_close(L, base, LUA_OK); /* there may be open upvalues */
updatestack(ci);
- if (nparams1) /* vararg function? */
- ci->func -= ci->u.l.nextraargs + nparams1;
}
+ if (nparams1) /* vararg function? */
+ ci->func -= ci->u.l.nextraargs + nparams1;
L->top = ra + n; /* set call for 'luaD_poscall' */
luaD_poscall(L, ci, n);
return;
