ref: 0d3f5d4bd7b74a810db4424aafdaf398faa9c69a
dir: /parse/fold.c/
#include <stdlib.h>
#include <stdio.h>
#include <inttypes.h>
#include <stdarg.h>
#include <ctype.h>
#include <string.h>
#include <assert.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include "util.h"
#include "parse.h"
size_t (*sizefn)(Node *n);
int
getintlit(Node *n, vlong *v)
{
Node *l;
if (exprop(n) != Olit)
return 0;
l = n->expr.args[0];
/* It's up to type checking to make sure this is ok */
if (l->lit.littype == Lint)
*v = l->lit.intval;
else if (l->lit.littype == Lchr)
*v = l->lit.chrval;
else
return 0;
return 1;
}
static int
isintval(Node *n, vlong val)
{
vlong v;
if (!getintlit(n, &v))
return 0;
return v == val;
}
static Node *
val(Srcloc loc, vlong val, Type *t)
{
Node *l, *n;
l = mkint(loc, val);
n = mkexpr(loc, Olit, l, NULL);
l->lit.type = t;
n->expr.type = t;
return n;
}
static int
issmallconst(Node *dcl)
{
Type *t;
if (!dcl->decl.isconst)
return 0;
if (!dcl->decl.init)
return 0;
t = tybase(exprtype(dcl->decl.init));
if (t->type <= Tyflt64)
return 1;
return 0;
}
static Node *
foldcast(Node *n)
{
Type *to, *from;
Node *sub;
sub = n->expr.args[0];
to = exprtype(n);
from = exprtype(sub);
switch (tybase(to)->type) {
case Tybool:
case Tyint8: case Tyint16: case Tyint32: case Tyint64:
case Tyuint8: case Tyuint16: case Tyuint32: case Tyuint64:
case Tyint: case Tyuint: case Tychar: case Tybyte:
case Typtr:
switch (tybase(from)->type) {
case Tybool:
case Tyint8: case Tyint16: case Tyint32: case Tyint64:
case Tyuint8: case Tyuint16: case Tyuint32: case Tyuint64:
case Tyint: case Tyuint: case Tychar: case Tybyte:
case Typtr:
if (exprop(sub) == Olit || tybase(from)->type == tybase(to)->type) {
sub->expr.type = to;
return sub;
} else {
return n;
}
default:
return n;
}
default:
return n;
}
return n;
}
int
idxcmp(const void *pa, const void *pb)
{
Node *a, *b;
vlong av, bv;
a = *(Node **)pa;
b = *(Node **)pb;
assert(getintlit(a->expr.idx, &av));
assert(getintlit(b->expr.idx, &bv));
/* don't trust overflow with int64 */
if (av < bv)
return -1;
else if (av == bv)
return 0;
else
return 1;
}
Node *
fold(Node *n, int foldvar)
{
Node **args, *r;
Type *t;
vlong a, b;
Ucon *uc;
size_t i;
if (!n)
return NULL;
if (n->type != Nexpr)
return n;
r = NULL;
args = n->expr.args;
if (n->expr.idx)
n->expr.idx = fold(n->expr.idx, foldvar);
for (i = 0; i < n->expr.nargs; i++)
args[i] = fold(args[i], foldvar);
switch (exprop(n)) {
case Outag:
if (exprop(args[0]) != Oucon)
break;
uc = finducon(tybase(exprtype(args[0])), args[0]->expr.args[0]);
r = val(n->loc, uc->id, exprtype(n));
break;
case Oudata:
if (exprop(args[0]) != Oucon || args[0]->expr.nargs != 2)
break;
r = args[0]->expr.args[1];
break;
case Ovar:
if (foldvar && issmallconst(decls[n->expr.did]))
r = fold(decls[n->expr.did]->decl.init, foldvar);
break;
case Oadd:
/* x + 0 = 0 */
if (isintval(args[0], 0))
r = args[1];
if (isintval(args[1], 0))
r = args[0];
if (getintlit(args[0], &a) && getintlit(args[1], &b))
r = val(n->loc, a + b, exprtype(n));
break;
case Osub:
/* x - 0 = 0 */
if (isintval(args[1], 0))
r = args[0];
if (getintlit(args[0], &a) && getintlit(args[1], &b))
r = val(n->loc, (uint64_t)a - b, exprtype(n));
break;
case Omul:
/* 1 * x = x */
if (isintval(args[0], 1))
r = args[1];
if (isintval(args[1], 1))
r = args[0];
/* 0 * x = 0 */
if (isintval(args[0], 0))
r = args[0];
if (isintval(args[1], 0))
r = args[1];
if (getintlit(args[0], &a) && getintlit(args[1], &b))
r = val(n->loc, a * b, exprtype(n));
break;
case Odiv:
/* x/0 = error */
if (isintval(args[1], 0))
fatal(args[1], "division by zero");
/* x/1 = x */
if (isintval(args[1], 1))
r = args[0];
/* 0/x = 0 */
if (isintval(args[1], 0))
r = args[1];
if (getintlit(args[0], &a) && getintlit(args[1], &b))
r = val(n->loc, a / b, exprtype(n));
break;
case Omod:
/* x%0 = error */
if (isintval(args[1], 0))
fatal(args[1], "division by zero");
/* x%1 = 0 */
if (isintval(args[1], 1))
r = val(n->loc, 0, exprtype(n));
if (getintlit(args[0], &a) && getintlit(args[1], &b))
r = val(n->loc, a % b, exprtype(n));
break;
case Oneg:
if (getintlit(args[0], &a))
r = val(n->loc, -a, exprtype(n));
break;
case Obsl:
if (getintlit(args[0], &a) && getintlit(args[1], &b))
r = val(n->loc, (uint64_t)a << b, exprtype(n));
break;
case Obsr:
if (getintlit(args[0], &a) && getintlit(args[1], &b))
r = val(n->loc, a >> b, exprtype(n));
break;
case Obor:
if (getintlit(args[0], &a) && getintlit(args[1], &b))
r = val(n->loc, a | b, exprtype(n));
break;
case Oband:
if (getintlit(args[0], &a) && getintlit(args[1], &b))
r = val(n->loc, a & b, exprtype(n));
break;
case Obxor:
if (getintlit(args[0], &a) && getintlit(args[1], &b))
r = val(n->loc, a ^ b, exprtype(n));
break;
case Omemb:
t = tybase(exprtype(args[0]));
/* we only fold lengths right now */
if (t->type == Tyarray && !strcmp(namestr(args[1]), "len")) {
r = t->asize;
r->expr.type = exprtype(n);
} else if (t->type == Tyunion && !strcmp(namestr(args[1]), "tag")) {
r = mkexpr(n->loc, Outag, args[0], NULL);
r->expr.type = mktype(n->loc, Tyint32);
}
break;
case Oarr:
if (n->expr.nargs > 0)
qsort(n->expr.args, n->expr.nargs, sizeof(Node*), idxcmp);
break;
case Ocast:
r = foldcast(n);
break;
case Osize:
if (sizefn)
r = val(n->loc, sizefn(n->expr.args[0]), exprtype(n));
break;
default:
break;
}
if (r && n->expr.idx)
r->expr.idx = n->expr.idx;
if (r)
return r;
else
return n;
}