The issue in PR56350 is two-fold. First, fix_loop_structure mishandles
latch edge computation (ugh). Second, RTL if-conversion, when merging
a latch block into sth else ends up generating stale latch block
references.
The following two patches cure that, adding some basic latch block
checking.
Bootstrap & regtest running on x86_64-unknown-linux-gnu.
Richard.
2013-02-18 Richard Biener <rguent...@suse.de>
PR middle-end/56349
* cfgloop.c (flow_loops_find): Reset latch before recomputing it.
(verify_loop_structure): Verify that a recorded latch is in fact
a latch.
Index: gcc/cfgloop.c
===================================================================
*** gcc/cfgloop.c (revision 196115)
--- gcc/cfgloop.c (working copy)
*************** flow_loops_find (struct loops *loops)
*** 466,471 ****
--- 466,473 ----
"loop %d with header %d\n",
loop->num, header->index);
}
+ /* Reset latch, we recompute it below. */
+ loop->latch = NULL;
larray.safe_push (loop);
}
*************** verify_loop_structure (void)
*** 1413,1418 ****
--- 1415,1433 ----
error ("loop %d%'s header does not have exactly 2 entries", i);
err = 1;
}
+ if (loop->latch)
+ {
+ if (!find_edge (loop->latch, loop->header))
+ {
+ error ("loop %d%'s latch does not have an edge to its header", i);
+ err = 1;
+ }
+ if (!dominated_by_p (CDI_DOMINATORS, loop->latch, loop->header))
+ {
+ error ("loop %d%'s latch is not dominated by its header", i);
+ err = 1;
+ }
+ }
if (loops_state_satisfies_p (LOOPS_HAVE_SIMPLE_LATCHES))
{
if (!single_succ_p (loop->latch))
2013-02-18 Richard Biener <rguent...@suse.de>
PR middle-end/56350
* cfghooks.c (merge_blocks): If we merge a latch into another
block adjust references to it.
* gcc.dg/torture/pr56350.c: New testcase.
Index: gcc/cfghooks.c
===================================================================
*** gcc/cfghooks.c (revision 196115)
--- gcc/cfghooks.c (working copy)
*************** merge_blocks (basic_block a, basic_block
*** 761,767 ****
{
e->src = a;
if (current_loops != NULL)
! rescan_loop_exit (e, true, false);
}
a->succs = b->succs;
a->flags |= b->flags;
--- 761,772 ----
{
e->src = a;
if (current_loops != NULL)
! {
! /* If b was a latch, a now is. */
! if (e->dest->loop_father->latch == b)
! e->dest->loop_father->latch = a;
! rescan_loop_exit (e, true, false);
! }
}
a->succs = b->succs;
a->flags |= b->flags;
Index: gcc/testsuite/gcc.dg/torture/pr56350.c
===================================================================
*** gcc/testsuite/gcc.dg/torture/pr56350.c (revision 0)
--- gcc/testsuite/gcc.dg/torture/pr56350.c (working copy)
***************
*** 0 ****
--- 1,41 ----
+ /* { dg-do compile } */
+
+ int a, b;
+ short c;
+
+ void f(void)
+ {
+ int a = 0;
+ int *k = 0;
+
+ for(; a < 2; a++);
+
+ if(!!(b |= a < 3) - 1)
+ {
+ if(0)
+ for (;; a++)
+ {
+ for (; c; *k = 0);
+ lbl1:
+ ;
+ }
+
+ for(; *k; k++)
+ {
+ c = b ? : a;
+
+ if (c)
+ lbl2:
+ b = 0;
+ }
+ goto lbl1;
+ }
+
+ for(;; b++)
+ {
+ if(b)
+ goto lbl2;
+
+ k = &b;
+ }
+ }
