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