ref: 2d00e8f657965583e906327bd4c0eff6953a71cd
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); static int getintlit(Node *n, vlong *v) { Node *l; if (exprop(n) != Olit) return 0; l = n->expr.args[0]; if (l->lit.littype != Lint) return 0; *v = l->lit.intval; 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); } 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; }