ref: 04c7c7f5989f7521ca68c8604b5b98b3bd4502bb
dir: /mi/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 "parse.h" #include "mi.h" static int islit(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 isval(Node *n, vlong val) { vlong v; if (!islit(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 Tylong: case Tyulong: 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 Tylong: case Tyulong: 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; } Node *fold(Node *n, int foldvar) { Node **args, *r; Type *t; vlong a, b; size_t i; if (!n) return NULL; if (n->type != Nexpr) return n; r = NULL; args = n->expr.args; for (i = 0; i < n->expr.nargs; i++) args[i] = fold(args[i], foldvar); switch (exprop(n)) { 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 (isval(args[0], 0)) r = args[1]; if (isval(args[1], 0)) r = args[0]; if (islit(args[0], &a) && islit(args[1], &b)) r = val(n->loc, a + b, exprtype(n)); break; case Osub: /* x - 0 = 0 */ if (isval(args[1], 0)) r = args[0]; if (islit(args[0], &a) && islit(args[1], &b)) r = val(n->loc, a - b, exprtype(n)); break; case Omul: /* 1 * x = x */ if (isval(args[0], 1)) r = args[1]; if (isval(args[1], 1)) r = args[0]; /* 0 * x = 0 */ if (isval(args[0], 0)) r = args[0]; if (isval(args[1], 0)) r = args[1]; if (islit(args[0], &a) && islit(args[1], &b)) r = val(n->loc, a * b, exprtype(n)); break; case Odiv: /* x/0 = error */ if (isval(args[1], 0)) fatal(args[1], "division by zero"); /* x/1 = x */ if (isval(args[1], 1)) r = args[0]; /* 0/x = 0 */ if (isval(args[1], 0)) r = args[1]; if (islit(args[0], &a) && islit(args[1], &b)) r = val(n->loc, a / b, exprtype(n)); break; case Omod: /* x%1 = x */ if (isval(args[1], 0)) r = args[0]; if (islit(args[0], &a) && islit(args[1], &b)) r = val(n->loc, a % b, exprtype(n)); break; case Oneg: if (islit(args[0], &a)) r = val(n->loc, -a, exprtype(n)); break; case Obsl: if (islit(args[0], &a) && islit(args[1], &b)) r = val(n->loc, a << b, exprtype(n)); break; case Obsr: if (islit(args[0], &a) && islit(args[1], &b)) r = val(n->loc, a >> b, exprtype(n)); break; case Obor: if (islit(args[0], &a) && islit(args[1], &b)) r = val(n->loc, a | b, exprtype(n)); break; case Oband: if (islit(args[0], &a) && islit(args[1], &b)) r = val(n->loc, a & b, exprtype(n)); break; case Obxor: if (islit(args[0], &a) && islit(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; break; case Ocast: r = foldcast(n); break; default: break; } if (r && n->expr.idx) r->expr.idx = n->expr.idx; if (r) return r; else return n; }