On July 19, 2016 7:27:30 PM GMT+02:00, Jakub Jelinek <ja...@redhat.com> wrote:
>Hi!
>
>Normally empty blocks without successors (result of
>__builtin_unreachable ()
>somewhere in RTL) aren't considered as forwarder_block_p, because they
>don't satisfy single_succ_p. But e.g. during cross-jumping fake edges
>to
>exit are added and then they suddenly satisfy this predicate, which
>confuses
>the cross-jumping among other things (normally cross-jumping attempts
>to be
>careful with no real successor blocks if there isn't a noreturn call
>with REG_ARGS_SIZE note, but if it believes those are forwarders, it
>doesn't
>check hard).
>
>Bootstrapped/regtested on x86_64-linux and i686-linux, ok for
>trunk/6.2?
OK.
Thanks,
Richard.
>2016-07-19 Jakub Jelinek <ja...@redhat.com>
>
> PR rtl-optimization/71916
> * cfgrtl.c (contains_no_active_insn_p): Return false also for
> bb which have a single succ fake edge.
>
> * gcc.c-torture/compile/pr71916.c: New test.
>
>--- gcc/cfgrtl.c.jj 2016-05-11 15:15:49.000000000 +0200
>+++ gcc/cfgrtl.c 2016-07-19 16:38:20.362303955 +0200
>@@ -574,8 +574,10 @@ contains_no_active_insn_p (const_basic_b
> {
> rtx_insn *insn;
>
>- if (bb == EXIT_BLOCK_PTR_FOR_FN (cfun) || bb ==
>ENTRY_BLOCK_PTR_FOR_FN (cfun)
>- || !single_succ_p (bb))
>+ if (bb == EXIT_BLOCK_PTR_FOR_FN (cfun)
>+ || bb == ENTRY_BLOCK_PTR_FOR_FN (cfun)
>+ || !single_succ_p (bb)
>+ || (single_succ_edge (bb)->flags & EDGE_FAKE) != 0)
> return false;
>
>for (insn = BB_HEAD (bb); insn != BB_END (bb); insn = NEXT_INSN (insn))
>--- gcc/testsuite/gcc.c-torture/compile/pr71916.c.jj 2016-07-19
>16:43:37.610371787 +0200
>+++ gcc/testsuite/gcc.c-torture/compile/pr71916.c 2016-07-19
>16:43:20.000000000 +0200
>@@ -0,0 +1,36 @@
>+/* PR rtl-optimization/71916 */
>+
>+int a, b, c, d, f, g;
>+short h;
>+
>+short
>+foo (short p1)
>+{
>+ return a >= 2 || p1 > 7 >> a ? p1 : p1 << a;
>+}
>+
>+void
>+bar (void)
>+{
>+ for (;;)
>+ {
>+ int i, j[3];
>+ h = b >= 2 ? d : d >> b;
>+ if (foo (f > h ^ c))
>+ {
>+ d = 0;
>+ while (f <= 2)
>+ {
>+ char k[2];
>+ for (;;)
>+ k[i++] = 7;
>+ }
>+ }
>+ else
>+ for (;;)
>+ g = j[2];
>+ if (g)
>+ for (;;)
>+ ;
>+ }
>+}
>
> Jakub
