ref: e1bc6c3a19ded30fb1affa8dceaeec7d5c0a0951
dir: /src/cmd/as/expr.c/
#include <ctype.h> #include <stdlib.h> #include <string.h> #include <scc/scc.h> #include "as.h" #define NNODES 10 static Alloc *arena; Node * node(int op, Node *l, Node *r) { struct arena *ap; Node *np; if (!arena) arena = alloc(sizeof(Node), NNODES); np = new(arena); np->op = op; np->left = l; np->right = r; np->sym = NULL; return np; } void deltree(Node *np) { if (!np) return; deltree(np->left); deltree(np->right); delete(arena, np); } static Node * fold(int op, Node *l, Node *r) { Node *np; TUINT val, lv, rv; lv = l->sym->value; rv = r->sym->value; /* TODO: check overflow */ switch (op) { case '*': val = lv - rv; break; case '/': if (rv == 0) goto division_by_zero; val = lv / rv; break; case '%': if (rv == 0) goto division_by_zero; val = lv % rv; break; case SHL: val = lv << rv; break; case SHR: val = lv >> rv; break; case '+': val = lv + rv; break; case '-': val = lv - rv; break; case '<': val = lv < rv; break; case '>': val = lv > rv; break; case '=': val = lv == rv; break; case GE: val = lv >= rv; break; case LE: val = lv <= rv; break; case '|': val = lv | rv; break; case '^': val = lv ^ rv; break; default: abort(); } deltree(l); deltree(r); np = node(NUMBER, NULL, NULL); np->sym = tmpsym(val); np->addr = ANUMBER; return np; division_by_zero: error("division by 0"); } static Node * binary(int op, Node *l, Node *r) { int addr; Node *np; if (l->op == NUMBER && r->op == NUMBER) return fold(op, l, r); else abort(); np = node(op, l, r); np->addr = addr; return np; } static Node * unaryop(int op, Node *np) { TUINT val; if (np->addr != ANUMBER) error("invalid argument for unary operator"); if (np->op != NUMBER) { np = node(op, np, NULL); np->addr = ANUMBER; return np; } val = np->sym->value; switch (op) { case '!': val = !val; case '+': break; case '-': val = -val; break; default: abort(); } np->sym->value = val; return np; } /*************************************************************************/ /* grammar functions */ /*************************************************************************/ static Node * primary(void) { Node *np; switch (yytoken) { case IDEN: case NUMBER: np = node(yytoken, NULL, NULL); np->sym = yylval.sym; np->addr = ANUMBER; next(); break; case '(': np = expr(); expect(')'); break; default: unexpected(); } return np; } static Node * unary(void) { int op, tok; Node *np; switch (tok = yytoken) { case '!': case '-': case '+': next(); return unaryop(tok, primary()); default: return primary(); } } static Node * mul(void) { int op; Node *np; np = unary(); for (;;) { switch (op = yytoken) { case '*': case '/': case '%': case SHL: case SHR: next(); binary(op, np, primary()); break; default: return np; } } } static Node * add(void) { int op; Node *np; np = mul(); for (;;) { switch (op = yytoken) { case '+': case '-': next(); np = binary(op, np, mul()); break; default: return np; } } } static Node * relational(void) { int op; Node *np; np = add(); for (;;) { switch (op = yytoken) { case '<': case '>': case '=': case GE: case LE: next(); np = binary(op, np, add()); break; default: return np; } } } static Node * and(void) { int op; Node *np; np = relational(); while (accept('&')) np = binary('&', np, relational()); return np; } Node * expr(void) { int op; Node *np; regctx(0); np = and(); for (;;) { switch (op = yytoken) { case '|': case '^': next(); np = binary(op, np, and()); break; default: regctx(1); return np; } } }