331 lines
6.8 KiB
C
331 lines
6.8 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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/* B R A N C H O P T I M I Z A T I O N
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*
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* B O . C
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <em_mnem.h>
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#include <em_pseu.h>
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#include <em_spec.h>
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#include <em_flag.h>
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#include "../share/types.h"
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#include "../share/debug.h"
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#include "../share/global.h"
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#include "../share/files.h"
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#include "../share/get.h"
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#include "../share/put.h"
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#include "../share/lset.h"
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#include "../share/map.h"
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#include "../share/alloc.h"
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#include "../share/utils.h"
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#include "../share/def.h"
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#include "../share/go.h"
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extern char em_flag[];
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#define LP_BLOCKS lp_extend->lpx_ra.lpx_blocks
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#define newbolpx() (lpext_p) newstruct(lpext_ra)
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#define oldbolpx(x) oldstruct(lpext_ra,x)
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STATIC int Sbo; /* #optimizations found */
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#define DLINK(l1,l2) l1->l_next=l2; l2->l_prev=l1
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/* This module performs some very simple branch optimizations.
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*
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* I) Look for pairs of basic blocks (B1,B2), such that
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* SUCC(b1) = {B2} and
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* PRED(B2) = {B1}.
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* In this case B1 and B2 can be combined into one block.
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* This optimization is mainly succesful:
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* 1) for switch statements in C, as the C compiler generates a branch
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* over the entire switch.
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* 2) for return statements, if the only way to return from a procedure
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* is via a return statement somewhere in the middle of the procedure.
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* II) Optimize while statements. Transformations like:
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* 1: jmp 2
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* tst cond 1:
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* beq 2f S
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* S 2:
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* jmp 1 tst cond
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* 2: bneq 1
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* are done by this optimization.
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*/
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STATIC line_p last_code(lines,skip_pseu)
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line_p lines;
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bool skip_pseu;
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{
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/* Determine the last line of a list */
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register line_p l;
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for (l = lines; l->l_next != (line_p) 0; l = l->l_next);
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if (skip_pseu) {
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while (l && (INSTR(l) < sp_fmnem || INSTR(l) > sp_lmnem)) l = PREV(l);
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}
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return l;
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}
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STATIC short cc_tab[12] =
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{op_blt,op_zlt,op_ble,op_zle,op_beq,op_zeq,
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op_zne,op_bne,op_zgt,op_bgt,op_zge,op_bge};
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STATIC short rev_cond(cond)
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short cond;
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{
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register i;
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for (i = 0; i < 12; i++) {
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if (cond == cc_tab[i]) return cc_tab[11-i];
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}
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return op_nop;
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}
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STATIC bool is_bcc(l)
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line_p l;
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{
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return rev_cond(INSTR(l)) != op_nop;
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}
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STATIC bo_optloop(p,b,x,bra,bcc)
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proc_p p;
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bblock_p b,x;
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line_p bra,bcc;
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{
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bblock_p prevb,n;
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line_p l;
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if (b->b_start == bra) {
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b->b_start = (line_p) 0;
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} else {
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PREV(bra)->l_next = (line_p) 0;
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}
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PREV(bra) = (line_p) 0;
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bcc->l_instr = rev_cond(INSTR(bcc));
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n = x->b_next;
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l = n->b_start;
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if (l == (line_p) 0 || INSTR(l) != op_lab) {
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l = newline(OPINSTRLAB);
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l->l_instr = op_lab;
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INSTRLAB(l) = freshlabel();
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if (n->b_start != (line_p) 0) {
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DLINK(l,n->b_start);
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}
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n->b_start = l;
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}
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INSTRLAB(bcc) = INSTRLAB(l);
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for (prevb = p->p_start; prevb != (bblock_p) 0 && prevb->b_next != x;
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prevb = prevb->b_next);
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if (prevb == (bblock_p) 0) {
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p->p_start = x->b_next;
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} else {
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prevb->b_next = x->b_next;
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l = last_instr(prevb);
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if (l == (line_p) 0) {
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prevb->b_start = bra;
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} else {
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if ((em_flag[INSTR(l)-sp_fmnem]&EM_FLO) == FLO_T) {
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oldline(bra);
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} else {
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appnd_line(bra,l);
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}
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}
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}
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x->b_next = b->b_next;
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b->b_next = x;
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}
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STATIC void bo_tryloop(p,loop)
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proc_p p;
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lset loop;
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{
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Lindex i,j;
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bblock_p b,x;
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line_p bra,bcc;
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for (i = Lfirst(loop); i != (Lindex) 0; i = Lnext(i,loop)) {
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b = (bblock_p) Lelem(i);
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if (b->b_next != (bblock_p) 0 && !Lis_elem(b->b_next,loop)) {
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j = Lfirst(b->b_succ);
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if (j != (Lindex) 0 &&
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(bra = last_instr(b)) != (line_p) 0 &&
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INSTR(bra) == op_bra) {
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x = (bblock_p) Lelem(j); /* single successor */
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if (Lis_elem(b->b_next,x->b_succ) &&
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is_bcc((bcc = last_instr(x)))) {
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OUTVERBOSE("branch optimization proc %d block %d\n", curproc->p_id,x->b_id);
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Sbo++;
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bo_optloop(p,b,x,bra,bcc);
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return;
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}
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}
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}
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}
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}
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STATIC bo_loops(p)
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proc_p p;
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{
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Lindex i;
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loop_p lp;
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for (i = Lfirst(p->p_loops); i != (Lindex) 0; i = Lnext(i,p->p_loops)) {
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lp = (loop_p) (Lelem(i));
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bo_tryloop(p,lp->LP_BLOCKS);
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}
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}
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STATIC mv_code(b1,b2)
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bblock_p b1,b2;
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{
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line_p l,x;
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l = last_code(b2->b_start,TRUE);
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assert(INSTR(l) == op_bra);
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DLINK(l,b1->b_start);
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x = l->l_next;
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rm_line(l,b2);
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if (INSTR(x) == op_lab) {
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rm_line(x,b2);
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}
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}
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void
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bo_switch(b)
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bblock_p b;
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{
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bblock_p s,x;
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Lindex i;
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line_p l,bra;
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if (Lnrelems(b->b_succ) == 1) {
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s = (bblock_p) Lelem(Lfirst(b->b_succ));
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if (b->b_start != (line_p) 0 &&
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s->b_start != (line_p) 0 &&
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Lnrelems(s->b_pred) == 1 &&
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(bra = last_code(b->b_start,TRUE)) != (line_p) 0 &&
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INSTR(bra) == op_bra &&
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(s->b_next == (bblock_p) 0 ||
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!Lis_elem(s->b_next,s->b_succ) ||
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((bra = last_code(s->b_start, TRUE)) != (line_p) 0 &&
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(em_flag[INSTR(bra)-sp_fmnem]&EM_FLO) == FLO_T))) {
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l = last_code(s->b_start,FALSE);
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if (INSTR(l) == ps_end) {
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if (PREV(l) == (line_p) 0) return;
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PREV(l)->l_next = (line_p) 0;
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PREV(l) = (line_p) 0;
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} else {
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l = (line_p) 0;
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}
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OUTVERBOSE("branch optimization in proc %d, block %d",curproc->p_id,b->b_id);
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Sbo++;
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Ldeleteset(b->b_succ);
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b->b_succ = s->b_succ;
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Ldeleteset(s->b_pred);
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s->b_succ = Lempty_set();
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s->b_pred = Lempty_set();
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for (i = Lfirst(b->b_succ); i != (Lindex) 0;
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i = Lnext(i,b->b_succ)) {
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x = (bblock_p) Lelem(i);
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Lremove(s,&x->b_pred);
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Ladd(b,&x->b_pred);
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if (x->b_idom == s) {
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x->b_idom = b;
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}
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}
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mv_code(s,b);
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s->b_start = l;
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}
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}
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}
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STATIC bo_extproc(p)
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proc_p p;
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{
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/* Allocate the extended data structures for procedure p */
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register loop_p lp;
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register Lindex pi;
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for (pi = Lfirst(p->p_loops); pi != (Lindex) 0;
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pi = Lnext(pi,p->p_loops)) {
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lp = (loop_p) Lelem(pi);
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lp->lp_extend = newbolpx();
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}
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}
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STATIC loop_blocks(p)
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proc_p p;
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{
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/* Compute the LP_BLOCKS sets for all loops of p */
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register bblock_p b;
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register Lindex i;
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for (b = p->p_start; b != (bblock_p) 0; b = b->b_next) {
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for (i = Lfirst(b->b_loops); i != (Lindex) 0;
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i = Lnext(i,b->b_loops)) {
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Ladd(b,&(((loop_p) Lelem(i))->LP_BLOCKS));
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}
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}
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}
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STATIC bo_cleanproc(p)
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proc_p p;
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{
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/* Allocate the extended data structures for procedure p */
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register loop_p lp;
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register Lindex pi;
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register bblock_p b;
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for (pi = Lfirst(p->p_loops); pi != (Lindex) 0;
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pi = Lnext(pi,p->p_loops)) {
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lp = (loop_p) Lelem(pi);
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oldbolpx(lp->lp_extend);
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}
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}
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void bo_optimize(void *vp)
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{
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proc_p p = vp;
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bblock_p b;
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if (IS_ENTERED_WITH_GTO(p)) return;
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bo_extproc(p);
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loop_blocks(p);
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bo_loops(p);
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for (b = p->p_start; b != 0; b = b->b_next) {
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bo_switch(b);
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}
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bo_cleanproc(p);
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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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go(argc,argv,no_action,bo_optimize,no_action,no_action);
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report("branch optimizations", Sbo);
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exit(0);
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}
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