/* * (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands. * See the copyright notice in the ACK home directory, in the file "Copyright". * * Author: Hans van Staveren */ #include "param.h" #include "types.h" #include "tes.h" #include #include #include #include "alloc.h" #include "line.h" #include "proinf.h" #include "optim.h" #include "ext.h" #include "flow.h" void flow() { findreach(); /* determine reachable labels */ cleaninstrs(); /* throw away unreachable code */ } void findreach() { num_p *npp,np; reach(instrs); for(npp=curpro.numhash;npp< &curpro.numhash[NNUMHASH]; npp++) for(np= *npp; np != (num_p) 0 ; np = np->n_next) if (np->n_flags&NUMDATA) { np->n_repl->n_flags |= NUMREACH; np->n_repl->n_jumps++; if (!(np->n_flags&NUMSCAN)) { np->n_flags |= NUMSCAN; if (np->n_line) { reach(np->n_line->l_next); continue; } if (!(np->n_repl->n_flags&NUMSCAN)) { np->n_repl->n_flags |= NUMSCAN; if (np->n_repl->n_line) reach(np->n_repl->n_line->l_next); } } } } void reach(line_p lnp) { num_p np; for (;lnp != (line_p) 0; lnp = lnp->l_next) { if(lnp->l_optyp == OPNUMLAB) { /* * Branch instruction or label */ np = lnp->l_a.la_np; if ((lnp->l_instr&BMASK) != op_lab) lnp->l_a.la_np = np = np->n_repl; np->n_flags |= NUMREACH; if (!(np->n_flags&NUMSCAN)) { np->n_flags |= NUMSCAN; if (np->n_line) reach(np->n_line->l_next); else { np = np->n_repl; np->n_flags |= NUMREACH; if (!(np->n_flags & NUMSCAN)) { np->n_flags |= NUMSCAN; if (np->n_line) reach(np->n_line->l_next); } } } if ((lnp->l_instr&BMASK) == op_lab) return; else np->n_jumps++; } if ((lnp->l_instr & BMASK) > sp_lmnem) continue; if ((em_flag[(lnp->l_instr&BMASK)-sp_fmnem]&EM_FLO)==FLO_T) return; } } void cleaninstrs() { line_p *lpp, lp, *lastbra; bool reachable, superfluous; int instr; lpp = &instrs; lastbra = (line_p *) 0; reachable = TRUE; while ((lp = *lpp) != (line_p) 0) { instr = lp->l_instr&BMASK; if (instr == op_lab) { if ((lp->l_a.la_np->n_flags&NUMREACH) != 0) { reachable = TRUE; if (lastbra != (line_p *) 0 && (*lastbra)->l_next == lp && (*lastbra)->l_a.la_np->n_repl==lp->l_a.la_np) { oldline(*lastbra); OPTIM(O_BRALAB); lpp = lastbra; *lpp = lp; lastbra = (line_p *) 0; lp->l_a.la_np->n_jumps--; } } if ( lp->l_a.la_np->n_repl != lp->l_a.la_np || ((lp->l_a.la_np->n_flags&NUMDATA)==0 && lp->l_a.la_np->n_jumps == 0)) superfluous = TRUE; else superfluous = FALSE; } else superfluous = FALSE; if ( (!reachable) || superfluous) { if (instr == op_lab) { lp->l_a.la_np->n_line = 0; } else if (instr > sp_lmnem) { /* leave pseudo's */ lpp = &lp->l_next; continue; } lp = lp->l_next; oldline(*lpp); OPTIM(O_UNREACH); *lpp = lp; } else { if ( instr <= sp_lmnem && (em_flag[instr-sp_fmnem]&EM_FLO)==FLO_T) { reachable = FALSE; if ((lp->l_instr&BMASK) == op_bra) lastbra = lpp; } lpp = &lp->l_next; } } }