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ack/util/ego/bo/bo.c
ceriel 15449606d1 bug fix: if a case-statement did not have a default, so that the 
default is the successor of the block containing the CSA/CSB instruction,
the branch to the CSA/CSB block was not optimized
1989-03-07 10:11:24 +00:00

331 lines
6.8 KiB
C
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/* $Header$ */
/*
* (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands.
* See the copyright notice in the ACK home directory, in the file "Copyright".
*/
/* B R A N C H O P T I M I Z A T I O N
*
* B O . C
*/
#include <stdio.h>
#include "../share/types.h"
#include "../share/debug.h"
#include "../share/global.h"
#include "../share/files.h"
#include "../share/get.h"
#include "../share/put.h"
#include "../share/lset.h"
#include "../share/map.h"
#include "../share/alloc.h"
#include "../share/aux.h"
#include "../share/def.h"
#include "../share/go.h"
#include "../../../h/em_mnem.h"
#include "../../../h/em_pseu.h"
#include "../../../h/em_spec.h"
#include "../../../h/em_flag.h"
extern char em_flag[];
#define LP_BLOCKS lp_extend->lpx_ra.lpx_blocks
#define newbolpx() (lpext_p) newstruct(lpext_ra)
#define oldbolpx(x) oldstruct(lpext_ra,x)
STATIC int Sbo; /* #optimizations found */
#define DLINK(l1,l2) l1->l_next=l2; l2->l_prev=l1
/* This module performs some very simple branch optimizations.
*
* I) Look for pairs of basic blocks (B1,B2), such that
* SUCC(b1) = {B2} and
* PRED(B2) = {B1}.
* In this case B1 and B2 can be combined into one block.
* This optimization is mainly succesful:
* 1) for switch statements in C, as the C compiler generates a branch
* over the entire switch.
* 2) for return statements, if the only way to return from a procedure
* is via a return statement somewhere in the middle of the procedure.
* II) Optimize while statements. Transformations like:
* 1: jmp 2
* tst cond 1:
* beq 2f S
* S 2:
* jmp 1 tst cond
* 2: bneq 1
* are done by this optimization.
*/
STATIC line_p last_code(lines,skip_pseu)
line_p lines;
bool skip_pseu;
{
/* Determine the last line of a list */
register line_p l;
for (l = lines; l->l_next != (line_p) 0; l = l->l_next);
if (skip_pseu) {
while (INSTR(l) < sp_fmnem || INSTR(l) > sp_lmnem) l = PREV(l);
}
return l;
}
STATIC short cc_tab[12] =
{op_blt,op_zlt,op_ble,op_zle,op_beq,op_zeq,
op_zne,op_bne,op_zgt,op_bgt,op_zge,op_bge};
STATIC short rev_cond(cond)
short cond;
{
register i;
for (i = 0; i < 12; i++) {
if (cond == cc_tab[i]) return cc_tab[11-i];
}
return op_nop;
}
STATIC bool is_bcc(l)
line_p l;
{
return rev_cond(INSTR(l)) != op_nop;
}
STATIC bo_optloop(p,b,x,bra,bcc)
proc_p p;
bblock_p b,x;
line_p bra,bcc;
{
bblock_p prevb,n;
line_p l;
if (b->b_start == bra) {
b->b_start = (line_p) 0;
} else {
PREV(bra)->l_next = (line_p) 0;
}
PREV(bra) = (line_p) 0;
bcc->l_instr = rev_cond(INSTR(bcc));
n = x->b_next;
l = n->b_start;
if (l == (line_p) 0 || INSTR(l) != op_lab) {
l = newline(OPINSTRLAB);
l->l_instr = op_lab;
INSTRLAB(l) = freshlabel();
if (n->b_start != (line_p) 0) {
DLINK(l,n->b_start);
}
n->b_start = l;
}
INSTRLAB(bcc) = INSTRLAB(l);
for (prevb = p->p_start; prevb != (bblock_p) 0 && prevb->b_next != x;
prevb = prevb->b_next);
if (prevb == (bblock_p) 0) {
p->p_start = x->b_next;
} else {
prevb->b_next = x->b_next;
l = last_instr(prevb);
if (l == (line_p) 0) {
prevb->b_start = bra;
} else {
if (INSTR(l) == op_bra &&
INSTRLAB(l) == INSTRLAB(bra)) {
oldline(bra);
} else {
appnd_line(bra,l);
}
}
}
x->b_next = b->b_next;
b->b_next = x;
}
STATIC bo_tryloop(p,loop)
proc_p p;
lset loop;
{
Lindex i,j;
bblock_p b,x;
line_p bra,bcc;
for (i = Lfirst(loop); i != (Lindex) 0; i = Lnext(i,loop)) {
b = (bblock_p) Lelem(i);
if (b->b_next != (bblock_p) 0 && !Lis_elem(b->b_next,loop)) {
j = Lfirst(b->b_succ);
if (j != (Lindex) 0 &&
(bra = last_instr(b)) != (line_p) 0 &&
INSTR(bra) == op_bra) {
x = (bblock_p) Lelem(j); /* single successor */
if (Lis_elem(b->b_next,x->b_succ) &&
is_bcc((bcc = last_instr(x)))) {
OUTVERBOSE("branch optimization proc %d block %d\n", curproc->p_id,x->b_id);
Sbo++;
bo_optloop(p,b,x,bra,bcc);
return;
}
}
}
}
}
STATIC bo_loops(p)
proc_p p;
{
Lindex i;
loop_p lp;
for (i = Lfirst(p->p_loops); i != (Lindex) 0; i = Lnext(i,p->p_loops)) {
lp = (loop_p) (Lelem(i));
bo_tryloop(p,lp->LP_BLOCKS);
}
}
STATIC mv_code(b1,b2)
bblock_p b1,b2;
{
line_p l,x;
l = last_code(b2->b_start,TRUE);
assert(INSTR(l) == op_bra);
DLINK(l,b1->b_start);
x = l->l_next;
rm_line(l,b2);
if (INSTR(x) == op_lab) {
rm_line(x,b2);
}
}
bo_switch(b)
bblock_p b;
{
bblock_p s,x;
Lindex i;
line_p l,bra;
if (Lnrelems(b->b_succ) == 1) {
s = (bblock_p) Lelem(Lfirst(b->b_succ));
if (b->b_start != (line_p) 0 &&
s->b_start != (line_p) 0 &&
Lnrelems(s->b_pred) == 1 &&
(bra = last_code(b->b_start,TRUE)) != (line_p) 0 &&
INSTR(bra) == op_bra &&
(s->b_next == (bblock_p) 0 ||
!Lis_elem(s->b_next,s->b_succ) ||
((bra = last_code(s->b_start, TRUE)) != (line_p) 0 &&
(em_flag[INSTR(bra)]&EM_FLO) == FLO_T))) {
l = last_code(s->b_start,FALSE);
if (INSTR(l) == ps_end) {
if (PREV(l) == (line_p) 0) return;
PREV(l)->l_next = (line_p) 0;
PREV(l) = (line_p) 0;
} else {
l = (line_p) 0;
}
OUTVERBOSE("branch optimization in proc %d, block %d",curproc->p_id,b->b_id);
Sbo++;
Ldeleteset(b->b_succ);
b->b_succ = s->b_succ;
Ldeleteset(s->b_pred);
s->b_succ = Lempty_set();
s->b_pred = Lempty_set();
for (i = Lfirst(b->b_succ); i != (Lindex) 0;
i = Lnext(i,b->b_succ)) {
x = (bblock_p) Lelem(i);
Lremove(s,&x->b_pred);
Ladd(b,&x->b_pred);
if (x->b_idom == s) {
x->b_idom = b;
}
}
mv_code(s,b);
s->b_start = l;
}
}
}
STATIC bo_extproc(p)
proc_p p;
{
/* Allocate the extended data structures for procedure p */
register loop_p lp;
register Lindex pi;
for (pi = Lfirst(p->p_loops); pi != (Lindex) 0;
pi = Lnext(pi,p->p_loops)) {
lp = (loop_p) Lelem(pi);
lp->lp_extend = newbolpx();
}
}
STATIC loop_blocks(p)
proc_p p;
{
/* Compute the LP_BLOCKS sets for all loops of p */
register bblock_p b;
register Lindex i;
for (b = p->p_start; b != (bblock_p) 0; b = b->b_next) {
for (i = Lfirst(b->b_loops); i != (Lindex) 0;
i = Lnext(i,b->b_loops)) {
Ladd(b,&(((loop_p) Lelem(i))->LP_BLOCKS));
}
}
}
STATIC bo_cleanproc(p)
proc_p p;
{
/* Allocate the extended data structures for procedure p */
register loop_p lp;
register Lindex pi;
register bblock_p b;
for (pi = Lfirst(p->p_loops); pi != (Lindex) 0;
pi = Lnext(pi,p->p_loops)) {
lp = (loop_p) Lelem(pi);
oldbolpx(lp->lp_extend);
}
}
bo_optimize(p)
proc_p p;
{
bblock_p b;
if (IS_ENTERED_WITH_GTO(p)) return;
bo_extproc(p);
loop_blocks(p);
bo_loops(p);
for (b = p->p_start; b != 0; b = b->b_next) {
bo_switch(b);
}
bo_cleanproc(p);
}
main(argc,argv)
int argc;
char *argv[];
{
go(argc,argv,no_action,bo_optimize,no_action,no_action);
report("branch optimizations", Sbo);
exit(0);
}
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