85 lines
2 KiB
C
85 lines
2 KiB
C
/* $Id$ */
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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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/* C O M M O N S U B E X P R E S S I O N E L I M I N A T I O N */
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#include <stdio.h>
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#include "../share/types.h"
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#include "../share/lset.h"
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#include "../share/debug.h"
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#include "../share/go.h"
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#include "cs.h"
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#include "cs_aux.h"
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#include "cs_avail.h"
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#include "cs_debug.h"
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#include "cs_elim.h"
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#include "cs_entity.h"
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#include "cs_profit.h"
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#include "cs_stack.h"
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#include "cs_vnm.h"
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int Scs; /* Number of optimizations found. */
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STATIC cs_clear()
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{
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clr_avails();
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clr_entities();
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clr_stack();
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start_valnum();
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}
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STATIC cs_optimize(p)
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proc_p p;
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{
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/* Optimize all basic blocks of one procedure. */
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register bblock_p rbp, bdone;
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if (IS_ENTERED_WITH_GTO(p)) return;
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avails = (avail_p) 0;
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entities = Lempty_set();
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cs_clear();
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rbp = p->p_start;
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while (rbp != (bblock_p) 0) {
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/* First we build a list of common expressions with the
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* value numbering algorithm. We take blocks in textual order
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* as long as the next block can only be reached through the
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* block we have just done. Note that if a block is preceded
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* by itself, the number of predecessors is greater than 1,
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* but the previous block can still be its immediate dominator.
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*/
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do { vnm(rbp); bdone = rbp;
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OUTTRACE("basic block %d processed", bdone->b_id);
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rbp = rbp->b_next;
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} while (rbp != (bblock_p) 0 && rbp->b_idom == bdone &&
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Lnrelems(rbp->b_pred) == 1
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);
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OUTTRACE("value numbering completed", 0);
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OUTAVAILS(); OUTENTITIES();
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/* Now we put out the instructions without common
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* subexpressions but with the use of temporaries,
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* which will be local variables of procedure p.
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*/
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eliminate(p);
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cs_clear();
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}
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}
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main(argc, argv)
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int argc;
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char *argv[];
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{
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Scs = 0;
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go(argc, argv, no_action, cs_optimize, cs_machinit, no_action);
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report("Duplicate expressions eliminated", Scs);
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exit(0);
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}
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