The following patch fixes (?) PR55833 by recomputing irreducible loops
after every unswitch-transformation. With this testcase, when we perform
loop unswitching on the RTL level, we end up in situation where we have
a loop into which we get through loop exit of another loop which is
a part of an irreducible region. Between those two loops is something like
preheader, which isn't marked as irreducible, nor its edges.
verify_loop_structure
then ICEs because of that. Another hunk of this patch is just cheaper checking,
written by Richi.
Regtested/bootstrapped on x86_64-linux.
Zdenek, any thoughts on this?
2013-01-10 Richard Biener <rguent...@suse.de>
Marek Polacek <pola...@redhat.com>
PR rtl-optimization/55833
* loop-unswitch.c (unswitch_loops): Move loop verification...
(unswitch_single_loop): ...here. Call mark_irreducible_loops.
* gcc.dg/pr55833.c: New test.
--- gcc/loop-unswitch.c.mp 2013-01-10 16:50:28.899559875 +0100
+++ gcc/loop-unswitch.c 2013-01-10 16:50:34.203575403 +0100
@@ -145,12 +145,7 @@ unswitch_loops (void)
/* Go through inner loops (only original ones). */
FOR_EACH_LOOP (li, loop, LI_ONLY_INNERMOST)
- {
- unswitch_single_loop (loop, NULL_RTX, 0);
-#ifdef ENABLE_CHECKING
- verify_loop_structure ();
-#endif
- }
+ unswitch_single_loop (loop, NULL_RTX, 0);
iv_analysis_done ();
}
@@ -370,6 +365,13 @@ unswitch_single_loop (struct loop *loop,
nloop = unswitch_loop (loop, bbs[i], copy_rtx_if_shared (cond), cinsn);
gcc_assert (nloop);
+ /* We changed the CFG. Recompute irreducible BBs and edges. */
+ mark_irreducible_loops ();
+
+#ifdef ENABLE_CHECKING
+ verify_loop_structure ();
+#endif
+
/* Invoke itself on modified loops. */
unswitch_single_loop (nloop, rconds, num + 1);
unswitch_single_loop (loop, conds, num + 1);
--- gcc/testsuite/gcc.dg/pr55833.c.mp 2013-01-10 17:23:26.016102692 +0100
+++ gcc/testsuite/gcc.dg/pr55833.c 2013-01-10 17:23:15.898073384 +0100
@@ -0,0 +1,28 @@
+/* PR rtl-optimization/55833 */
+/* { dg-do compile } */
+/* { dg-options "-O3" } */
+
+int a, b, c;
+
+void foo()
+{
+ unsigned d, l, *p, k = 1;
+
+ if(bar())
+ {
+label:
+ if((a = a <= 0))
+ {
+ if(c)
+ d = b;
+
+ if (b || d ? l : k ? : 0)
+ a = d = 0;
+
+ goto label;
+ }
+ }
+
+ while(*p++)
+ goto label;
+}
Marek
