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#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <stdarg.h>
#include <ctype.h>
#include <string.h>
#include <assert.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include "util.h"
#include "parse.h"
#include "mi.h"
#include "asm.h"
/* we sometimes leave dead code generated after
* a non-conditional jump. This code scans for
* the non-conditional exit from the BB, and truncate
* at that point */
static void
deadcode(Isel *s, Asmbb *bb)
{
size_t i;
if (!bb)
return;
for (i = 0; i < bb->ni; i++) {
if (bb->il[i]->op == Ijmp) {
i++;
break;
}
}
bb->ni = i;
}
/* checks for of dumb jump code.
* nop jumps:
* jmp .l1
* .l1:
* TODO: check for jumps over jumps.
*/
static void
nopjmp(Isel *s, Asmbb *bb, size_t idx)
{
Insn *jmp;
Loc *targ;
Asmbb *nextbb;
size_t i;
/* skip empty bbs */
if (!bb || !bb->ni)
return;
/* find the target of the last unconditional
* jump in the bb */
targ = NULL;
if (bb->il[bb->ni - 1]->op == Ijmp) {
jmp = bb->il[bb->ni - 1];
if (jmp->args[0]->type == Loclbl)
targ = jmp->args[0];
}
if (!targ)
return;
/* figure out if it's somewhere in the head of the next bb */
nextbb = NULL;
for (i = idx + 1; i < s->nbb; i++) {
nextbb = s->bb[i];
if (nextbb)
break;
}
if (!nextbb)
return;
for (i = 0; i < nextbb->nlbls; i++) {
if (!strcmp(nextbb->lbls[i], targ->lbl)) {
bb->ni--;
break;
}
}
}
void
peep(Isel *s)
{
size_t i;
for (i = 0; i < s->nbb; i++) {
deadcode(s, s->bb[i]);
nopjmp(s, s->bb[i], i);
}
}
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