commit 8eca21c2e85625390a2a3b08c231e75e315980b0
parent 924bed7297d5ea16a78ec07e7acc64afad951aa8
Author: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Mon, 1 Jul 2019 12:42:04 -0300
First take on constant propagation
Diffstat:
4 files changed, 73 insertions(+), 26 deletions(-)
diff --git a/lcode.c b/lcode.c
@@ -52,7 +52,7 @@ l_noret luaK_semerror (LexState *ls, const char *msg) {
** If expression is a numeric constant, fills 'v' with its value
** and returns 1. Otherwise, returns 0.
*/
-static int tonumeral(const expdesc *e, TValue *v) {
+int luaK_tonumeral (FuncState *fs, const expdesc *e, TValue *v) {
if (hasjumps(e))
return 0; /* not a numeral */
switch (e->k) {
@@ -62,12 +62,42 @@ static int tonumeral(const expdesc *e, TValue *v) {
case VKFLT:
if (v) setfltvalue(v, e->u.nval);
return 1;
+ case VUPVAL: { /* may be a constant */
+ Vardesc *vd = luaY_getvardesc(&fs, e);
+ if (v && vd && !ttisnil(&vd->val)) {
+ setobj(fs->ls->L, v, &vd->val);
+ return 1;
+ } /* else */
+ } /* FALLTHROUGH */
default: return 0;
}
}
/*
+** If expression 'e' is a constant, change 'e' to represent
+** the constant value.
+*/
+static int const2exp (FuncState *fs, expdesc *e) {
+ Vardesc *vd = luaY_getvardesc(&fs, e);
+ if (vd) {
+ TValue *v = &vd->val;
+ switch (ttypetag(v)) {
+ case LUA_TNUMINT:
+ e->k = VKINT;
+ e->u.ival = ivalue(v);
+ return 1;
+ case LUA_TNUMFLT:
+ e->k = VKFLT;
+ e->u.nval = fltvalue(v);
+ return 1;
+ }
+ }
+ return 0;
+}
+
+
+/*
** Return the previous instruction of the current code. If there
** may be a jump target between the current instruction and the
** previous one, return an invalid instruction (to avoid wrong
@@ -683,8 +713,10 @@ void luaK_dischargevars (FuncState *fs, expdesc *e) {
break;
}
case VUPVAL: { /* move value to some (pending) register */
- e->u.info = luaK_codeABC(fs, OP_GETUPVAL, 0, e->u.var.idx, 0);
- e->k = VRELOC;
+ if (!const2exp(fs, e)) {
+ e->u.info = luaK_codeABC(fs, OP_GETUPVAL, 0, e->u.var.idx, 0);
+ e->k = VRELOC;
+ }
break;
}
case VINDEXUP: {
@@ -1218,9 +1250,11 @@ static int validop (int op, TValue *v1, TValue *v2) {
** (In this case, 'e1' has the final result.)
*/
static int constfolding (FuncState *fs, int op, expdesc *e1,
- const expdesc *e2) {
+ const expdesc *e2) {
TValue v1, v2, res;
- if (!tonumeral(e1, &v1) || !tonumeral(e2, &v2) || !validop(op, &v1, &v2))
+ if (!luaK_tonumeral(fs, e1, &v1) ||
+ !luaK_tonumeral(fs, e2, &v2) ||
+ !validop(op, &v1, &v2))
return 0; /* non-numeric operands or not safe to fold */
luaO_rawarith(fs->ls->L, op, &v1, &v2, &res); /* does operation */
if (ttisinteger(&res)) {
@@ -1307,7 +1341,7 @@ static void codearith (FuncState *fs, OpCode op,
expdesc *e1, expdesc *e2, int flip, int line) {
if (isSCint(e2)) /* immediate operand? */
codebini(fs, cast(OpCode, op - OP_ADD + OP_ADDI), e1, e2, flip, line);
- else if (tonumeral(e2, NULL) && luaK_exp2K(fs, e2)) { /* K operand? */
+ else if (luaK_tonumeral(fs, e2, NULL) && luaK_exp2K(fs, e2)) { /* K operand? */
int v2 = e2->u.info; /* K index */
op = cast(OpCode, op - OP_ADD + OP_ADDK);
finishbinexpval(fs, e1, e2, op, v2, flip, line);
@@ -1328,7 +1362,7 @@ static void codearith (FuncState *fs, OpCode op,
static void codecommutative (FuncState *fs, OpCode op,
expdesc *e1, expdesc *e2, int line) {
int flip = 0;
- if (tonumeral(e1, NULL)) { /* is first operand a numeric constant? */
+ if (luaK_tonumeral(fs, e1, NULL)) { /* is first operand a numeric constant? */
swapexps(e1, e2); /* change order */
flip = 1;
}
@@ -1451,7 +1485,7 @@ void luaK_prefix (FuncState *fs, UnOpr op, expdesc *e, int line) {
case OPR_MINUS: case OPR_BNOT: /* use 'ef' as fake 2nd operand */
if (constfolding(fs, op + LUA_OPUNM, e, &ef))
break;
- /* FALLTHROUGH */
+ /* else */ /* FALLTHROUGH */
case OPR_LEN:
codeunexpval(fs, cast(OpCode, op + OP_UNM), e, line);
break;
@@ -1466,6 +1500,7 @@ void luaK_prefix (FuncState *fs, UnOpr op, expdesc *e, int line) {
** 2nd operand.
*/
void luaK_infix (FuncState *fs, BinOpr op, expdesc *v) {
+ luaK_dischargevars(fs, v);
switch (op) {
case OPR_AND: {
luaK_goiftrue(fs, v); /* go ahead only if 'v' is true */
@@ -1484,13 +1519,13 @@ void luaK_infix (FuncState *fs, BinOpr op, expdesc *v) {
case OPR_MOD: case OPR_POW:
case OPR_BAND: case OPR_BOR: case OPR_BXOR:
case OPR_SHL: case OPR_SHR: {
- if (!tonumeral(v, NULL))
+ if (!luaK_tonumeral(fs, v, NULL))
luaK_exp2anyreg(fs, v);
/* else keep numeral, which may be folded with 2nd operand */
break;
}
case OPR_EQ: case OPR_NE: {
- if (!tonumeral(v, NULL))
+ if (!luaK_tonumeral(fs, v, NULL))
luaK_exp2RK(fs, v);
/* else keep numeral, which may be an immediate operand */
break;
@@ -1535,17 +1570,16 @@ static void codeconcat (FuncState *fs, expdesc *e1, expdesc *e2, int line) {
*/
void luaK_posfix (FuncState *fs, BinOpr opr,
expdesc *e1, expdesc *e2, int line) {
+ luaK_dischargevars(fs, e2);
switch (opr) {
case OPR_AND: {
- lua_assert(e1->t == NO_JUMP); /* list closed by 'luK_infix' */
- luaK_dischargevars(fs, e2);
+ lua_assert(e1->t == NO_JUMP); /* list closed by 'luaK_infix' */
luaK_concat(fs, &e2->f, e1->f);
*e1 = *e2;
break;
}
case OPR_OR: {
- lua_assert(e1->f == NO_JUMP); /* list closed by 'luK_infix' */
- luaK_dischargevars(fs, e2);
+ lua_assert(e1->f == NO_JUMP); /* list closed by 'luaK_infix' */
luaK_concat(fs, &e2->t, e1->t);
*e1 = *e2;
break;
diff --git a/lcode.h b/lcode.h
@@ -51,6 +51,7 @@ typedef enum UnOpr { OPR_MINUS, OPR_BNOT, OPR_NOT, OPR_LEN, OPR_NOUNOPR } UnOpr;
#define luaK_jumpto(fs,t) luaK_patchlist(fs, luaK_jump(fs), t)
+LUAI_FUNC int luaK_tonumeral (FuncState *fs, const expdesc *e, TValue *v);
LUAI_FUNC int luaK_codeABx (FuncState *fs, OpCode o, int A, unsigned int Bx);
LUAI_FUNC int luaK_codeAsBx (FuncState *fs, OpCode o, int A, int Bx);
LUAI_FUNC int luaK_codeABCk (FuncState *fs, OpCode o, int A,
diff --git a/lparser.c b/lparser.c
@@ -206,6 +206,7 @@ static Vardesc *new_localvar (LexState *ls, TString *name) {
var = &dyd->actvar.arr[dyd->actvar.n++];
var->idx = cast(short, reg);
var->ro = 0;
+ setnilvalue(&var->val);
return var;
}
@@ -238,7 +239,7 @@ static LocVar *getlocvar (FuncState *fs, int i) {
** where that variable was defined. Return NULL if expression
** is neither a local variable nor an upvalue.
*/
-static Vardesc *getvardesc (FuncState **fs, expdesc *e) {
+Vardesc *luaY_getvardesc (FuncState **fs, const expdesc *e) {
if (e->k == VLOCAL)
return getlocalvardesc(*fs, e->u.var.idx);
else if (e->k != VUPVAL)
@@ -261,7 +262,7 @@ static Vardesc *getvardesc (FuncState **fs, expdesc *e) {
static void check_readonly (LexState *ls, expdesc *e) {
FuncState *fs = ls->fs;
- Vardesc *vardesc = getvardesc(&fs, e);
+ Vardesc *vardesc = luaY_getvardesc(&fs, e);
if (vardesc && vardesc->ro) { /* is variable local and const? */
const char *msg = luaO_pushfstring(ls->L,
"attempt to assign to const variable '%s'",
@@ -1678,20 +1679,13 @@ static void commonlocalstat (LexState *ls) {
static void tocloselocalstat (LexState *ls, Vardesc *var) {
FuncState *fs = ls->fs;
var->ro = 1; /* to-be-closed variables are always read-only */
- markupval(fs, fs->nactvar);
+ markupval(fs, fs->nactvar + 1);
fs->bl->insidetbc = 1; /* in the scope of a to-be-closed variable */
- luaK_codeABC(fs, OP_TBC, fs->nactvar - 1, 0, 0);
+ luaK_codeABC(fs, OP_TBC, fs->nactvar, 0, 0);
}
-static void attriblocalstat (LexState *ls) {
- Vardesc *var;
- TString *attr = str_checkname(ls);
- testnext(ls, '>');
- var = new_localvar(ls, str_checkname(ls));
- checknext(ls, '=');
- exp1(ls);
- adjustlocalvars(ls, 1);
+static void checkattrib (LexState *ls, TString *attr, Vardesc *var) {
if (strcmp(getstr(attr), "const") == 0)
var->ro = 1; /* set variable as read-only */
else if (strcmp(getstr(attr), "toclose") == 0)
@@ -1702,6 +1696,22 @@ static void attriblocalstat (LexState *ls) {
}
+static void attriblocalstat (LexState *ls) {
+ FuncState *fs = ls->fs;
+ Vardesc *var;
+ expdesc e;
+ TString *attr = str_checkname(ls);
+ testnext(ls, '>');
+ var = new_localvar(ls, str_checkname(ls));
+ checknext(ls, '=');
+ expr(ls, &e);
+ checkattrib(ls, attr, var);
+ luaK_tonumeral(fs, &e, &var->val);
+ luaK_exp2nextreg(fs, &e);
+ adjustlocalvars(ls, 1);
+}
+
+
static void localstat (LexState *ls) {
/* stat -> LOCAL NAME {',' NAME} ['=' explist]
| LOCAL *toclose NAME '=' exp */
diff --git a/lparser.h b/lparser.h
@@ -81,6 +81,7 @@ typedef struct expdesc {
/* description of an active local variable */
typedef struct Vardesc {
+ TValue val; /* constant value (if variable is 'const') */
short idx; /* index of the variable in the Proto's 'locvars' array */
lu_byte ro; /* true if variable is 'const' */
} Vardesc;
@@ -143,6 +144,7 @@ typedef struct FuncState {
} FuncState;
+LUAI_FUNC Vardesc *luaY_getvardesc (FuncState **fs, const expdesc *e);
LUAI_FUNC LClosure *luaY_parser (lua_State *L, ZIO *z, Mbuffer *buff,
Dyndata *dyd, const char *name, int firstchar);
