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constant folding and API arithmetic with integers

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This commit is contained in:
Roberto Ierusalimschy
2013-05-02 09:37:24 -03:00
parent 6920a7f2e3
commit 67532d5a10
4 changed files with 83 additions and 31 deletions
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47
lcode.c
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@@ -1,5 +1,5 @@
/*
** $Id: lcode.c,v 2.66 2013/04/26 13:07:53 roberto Exp roberto $
** $Id: lcode.c,v 2.67 2013/04/29 16:57:48 roberto Exp roberto $
** Code generator for Lua
** See Copyright Notice in lua.h
*/
@@ -29,8 +29,18 @@
#define hasjumps(e) ((e)->t != (e)->f)
static int isnumeral(expdesc *e) {
return (e->k == VKFLT && e->t == NO_JUMP && e->f == NO_JUMP);
static int tonumeral(expdesc *e, TValue *v) {
if (e->t != NO_JUMP || e->f != NO_JUMP)
return 0; /* not a numeral */
switch (e->k) {
case VKINT:
if (v) setivalue(v, e->u.ival);
return 1;
case VKFLT:
if (v) setnvalue(v, e->u.nval);
return 1;
default: return 0;
}
}
@@ -730,21 +740,28 @@ void luaK_indexed (FuncState *fs, expdesc *t, expdesc *k) {
static int constfolding (OpCode op, expdesc *e1, expdesc *e2) {
lua_Number r;
if (!isnumeral(e1) || !isnumeral(e2)) return 0;
if ((op == OP_DIV || op == OP_IDIV || op == OP_MOD) && e2->u.nval == 0)
return 0; /* do not attempt to divide by 0 */
r = luaO_numarith(op - OP_ADD + LUA_OPADD, e1->u.nval, e2->u.nval);
e1->u.nval = r;
TValue v1, v2, res;
lua_Integer i2;
if (!tonumeral(e1, &v1) || !tonumeral(e2, &v2))
return 0;
if ((op == OP_IDIV || op == OP_MOD) && tointeger(&v2, &i2) && i2 == 0)
return 0; /* avoid division by 0 at compile time */
luaO_arith(NULL, op - OP_ADD + LUA_OPADD, &v1, &v2, &res);
if (ttisinteger(&res)) {
e1->k = VKINT;
e1->u.ival = ivalue(&res);
}
else {
e1->k = VKFLT;
e1->u.nval = fltvalue(&res);
}
return 1;
}
static void codearith (FuncState *fs, OpCode op,
expdesc *e1, expdesc *e2, int line) {
if (constfolding(op, e1, e2))
return;
else {
if (!constfolding(op, e1, e2)) { /* could not fold operation? */
int o2 = (op != OP_UNM && op != OP_LEN) ? luaK_exp2RK(fs, e2) : 0;
int o1 = luaK_exp2RK(fs, e1);
if (o1 > o2) {
@@ -783,9 +800,7 @@ void luaK_prefix (FuncState *fs, UnOpr op, expdesc *e, int line) {
e2.t = e2.f = NO_JUMP; e2.k = VKFLT; e2.u.nval = 0;
switch (op) {
case OPR_MINUS: {
if (isnumeral(e)) /* minus constant? */
e->u.nval = luai_numunm(NULL, e->u.nval); /* fold it */
else {
if (!constfolding(OP_UNM, e, e)) { /* cannot fold it? */
luaK_exp2anyreg(fs, e);
codearith(fs, OP_UNM, e, &e2, line);
}
@@ -819,7 +834,7 @@ void luaK_infix (FuncState *fs, BinOpr op, expdesc *v) {
case OPR_ADD: case OPR_SUB:
case OPR_MUL: case OPR_DIV: case OPR_IDIV:
case OPR_MOD: case OPR_POW: {
if (!isnumeral(v)) luaK_exp2RK(fs, v);
if (!tonumeral(v, NULL)) luaK_exp2RK(fs, v);
break;
}
default: {