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fix edge deletion bug in sccp

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When an edge is deleted, the phis and predecessors of the
destination block have to be updated.  This is what blkdel()
was doing, but at a level too coarse.  The new function
edgedel() allows to remove a single edge (and takes care of
multiple edges).
This commit is contained in:
Quentin Carbonneaux 2017-02-06 14:38:47 -05:00
parent 1a76fd11f5
commit 8215b50a10
3 changed files with 34 additions and 28 deletions
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2
all.h
View file

@ -547,7 +547,7 @@ void err(char *, ...) __attribute__((noreturn));
/* cfg.c */
Blk *blknew(void);
void blkdel(Blk *);
void edgedel(Blk *, Blk **);
void fillpreds(Fn *);
void fillrpo(Fn *);
void filldom(Fn *);

48
cfg.c
View file

@ -12,32 +12,33 @@ blknew()
}
void
blkdel(Blk *b)
edgedel(Blk *bs, Blk **pbd)
{
Blk *s, **ps, *succ[3];
Blk *bd;
Phi *p;
uint a;
int mult;
succ[0] = b->s1;
succ[1] = b->s2 == b->s1 ? 0 : b->s2;
succ[2] = 0;
for (ps=succ; (s=*ps); ps++) {
for (p=s->phi; p; p=p->link) {
for (a=0; p->blk[a]!=b; a++)
assert(a+1<p->narg);
p->narg--;
memmove(&p->blk[a], &p->blk[a+1],
sizeof p->blk[0] * (p->narg-a));
memmove(&p->arg[a], &p->arg[a+1],
sizeof p->arg[0] * (p->narg-a));
}
if (s->npred != 0) {
for (a=0; s->pred[a]!=b; a++)
assert(a+1<s->npred);
s->npred--;
memmove(&s->pred[a], &s->pred[a+1],
sizeof s->pred[0] * (s->npred-a));
}
bd = *pbd;
mult = 1 + (bs->s1 == bs->s2);
*pbd = 0;
if (!bd || mult > 1)
return;
for (p=bd->phi; p; p=p->link) {
for (a=0; p->blk[a]!=bs; a++)
assert(a+1<p->narg);
p->narg--;
memmove(&p->blk[a], &p->blk[a+1],
sizeof p->blk[0] * (p->narg-a));
memmove(&p->arg[a], &p->arg[a+1],
sizeof p->arg[0] * (p->narg-a));
}
if (bd->npred != 0) {
for (a=0; bd->pred[a]!=bs; a++)
assert(a+1<bd->npred);
bd->npred--;
memmove(&bd->pred[a], &bd->pred[a+1],
sizeof bd->pred[0] * (bd->npred-a));
}
}
@ -110,7 +111,8 @@ fillrpo(Fn *f)
f->rpo = alloc(f->nblk * sizeof f->rpo[0]);
for (p=&f->start; (b=*p);) {
if (b->id == -1u) {
blkdel(b);
edgedel(b, &b->s1);
edgedel(b, &b->s2);
*p = b->link;
} else {
b->id -= n;

12
fold.c
View file

@ -275,7 +275,8 @@ fold(Fn *fn)
d = 1;
if (debug['F'])
fprintf(stderr, "%s ", b->name);
blkdel(b);
edgedel(b, &b->s1);
edgedel(b, &b->s2);
*pb = b->link;
continue;
}
@ -296,11 +297,14 @@ fold(Fn *fn)
renref(&i->arg[n]);
renref(&b->jmp.arg);
if (b->jmp.type == Jjnz && rtype(b->jmp.arg) == RCon) {
b->jmp.type = Jjmp;
if (czero(&fn->con[b->jmp.arg.val], 0))
if (czero(&fn->con[b->jmp.arg.val], 0)) {
edgedel(b, &b->s1);
b->s1 = b->s2;
b->s2 = 0;
} else
edgedel(b, &b->s2);
b->jmp.type = Jjmp;
b->jmp.arg = R;
b->s2 = 0;
}
pb = &b->link;
}