192 lines
4 KiB
C
192 lines
4 KiB
C
/*
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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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/* S T R E N G T H R E D U C T I O N
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*
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* S R _ C A N D . C
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*/
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#include "../share/types.h"
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#include "../../../h/em_mnem.h"
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#include "../../../h/em_pseu.h"
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#include "../share/lset.h"
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#include "../share/cset.h"
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#include "../share/debug.h"
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#include "../share/global.h"
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#include "../share/map.h"
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#include "../share/aux.h"
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#include "sr.h"
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#include "sr_aux.h"
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#include "sr_cand.h"
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/* A candidate induction variable of a loop (hereafter called candidate) is a
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* local variable (of the current procedure) that is assigned a value
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* precisely once within the loop. Furthermore, this assignment must
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* take place in a firm block of the loop.
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* We determine those locals that are assigned precisely once, within
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* a firm block;
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*
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* We represent a local variable via an instruction that references it,
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* e.g. LOL -6 represents the local variable at offset -6 with size=wordsize.
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* We keep track of two sets:
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* cand - the set of all candidate variables
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* dismiss - a set of variables that may not be made a candidate
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* (because they are assigned more than once, or because
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* they are assigned outside a firm block).
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* Only local variables for which a register message is given are considered.
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*/
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STATIC lset cand, /* set of candidates */
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dism; /* set of dismissed variables */
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#define ALL_LINES(lnp,list) lnp = list; lnp != (line_p) 0; lnp = lnp->l_next
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STATIC un_cand(lnp)
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line_p lnp;
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{
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/* remove the variable stored into by lnp from the list of
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* candidates (if it was there anyway).
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*/
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Lindex i, next;
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for (i = Lfirst(cand); i != (Lindex) 0; i = next) {
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next = Lnext(i,cand);
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if (same_local(lnp,Lelem(i))) {
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OUTTRACE("remove candidate",0);
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Lremove(Lelem(i), &cand);
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}
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}
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}
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STATIC bool is_cand(lnp)
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line_p lnp;
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{
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/* see if the variable stored into by lnp is a candate */
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Lindex i;
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for (i = Lfirst(cand); i != (Lindex) 0; i = Lnext(i,cand)) {
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if (same_local(lnp,Lelem(i))) {
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return TRUE;
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}
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}
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return FALSE;
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}
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STATIC make_cand(lnp)
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line_p lnp;
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{
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/* make the variable stored into by lnp a candidate */
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OUTTRACE("add a new candidate",0);
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Ladd(lnp,&cand);
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}
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STATIC do_dismiss(lnp)
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line_p lnp;
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{
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Ladd(lnp,&dism);
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}
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STATIC dismiss(lnp)
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line_p lnp;
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{
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/* The variable referenced by lnp is turned definitely into
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* a non-candidate.
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*/
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un_cand(lnp); /* remove it from the candidate set,
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* if it was there in the first place.
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*/
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do_dismiss(lnp); /* add it to the set of dismissed variables */
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}
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STATIC bool not_dismissed(lnp)
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line_p lnp;
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{
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Lindex i;
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for (i = Lfirst(dism); i != (Lindex) 0; i = Lnext(i,dism)) {
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if (same_local(Lelem(i),lnp)) {
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return FALSE; /* variable was dismissed */
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}
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}
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return TRUE;
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}
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STATIC try_cand(lnp,b)
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line_p lnp;
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bblock_p b;
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{
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/* If the variable stored into by lnp was not already a candidate
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* and was not dismissed, then it is made a candidate
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* (unless the assignment takes places in a block that is not firm).
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*/
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if (!is_regvar(off_set(lnp))) return;
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if (is_cand(lnp) || !IS_FIRM(b)) {
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dismiss(lnp);
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} else {
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if (not_dismissed(lnp)) {
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make_cand(lnp);
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}
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}
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}
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candidates(lp,cand_out,vars_out)
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loop_p lp;
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lset *cand_out, *vars_out;
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{
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/* Find the candidate induction variables.
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*/
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bblock_p b;
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line_p lnp;
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Lindex i;
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OUTTRACE("find candidates of loop %d",lp->lp_id);
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cand = Lempty_set();
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dism = Lempty_set();
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for (i = Lfirst(lp->LP_BLOCKS); i != (Lindex) 0;
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i = Lnext(i,lp->LP_BLOCKS)) {
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b = (bblock_p) Lelem(i);
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for ( ALL_LINES(lnp, b->b_start)) {
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OUTTRACE("inspect instruction %d",INSTR(lnp));
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switch(INSTR(lnp)) {
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case op_stl:
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case op_inl:
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case op_del:
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OUTTRACE("it's a store local",0);
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try_cand(lnp,b);
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break;
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case op_zrl:
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OUTTRACE("it's a destroy local",0);
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if (is_regvar(off_set(lnp))) {
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dismiss(lnp);
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}
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break;
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}
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}
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}
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*cand_out = cand;
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*vars_out = dism;
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}
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