On Fri, Jan 09, 2015 at 11:59:44AM +0100, Richard Biener wrote:
> > If you want, I can try instead of disabling it for tablejumps
> > just move the label.
>
> Yeah, I'd prefer that - it can't be too difficult, no?
So like this (tested just on the testcase, fully bootstrap/regtest
will follow)?
> > Still, I think we should be able to optimize it somewhere else too
> > (we can remove the tablejumps not just if all jump_table_data entries
> > point to next_bb, but even when they point to some completely different bb,
> > as long as it is a single_succ_p). And ideally also optimize it at GIMPLE,
> > but guess that is GCC 6 material.
>
> cfgcleanup material, similar for GIMPLE I guess.
You mean that cfgcleanup changes are GCC 6 material too?
2015-01-09 Jakub Jelinek <ja...@redhat.com>
PR rtl-optimization/64536
* cfgrtl.c (rtl_tidy_fallthru_edge): Handle removal of degenerate
tablejumps.
* gcc.dg/pr64536.c: New test.
--- gcc/cfgrtl.c.jj 2015-01-08 18:10:23.616598916 +0100
+++ gcc/cfgrtl.c 2015-01-09 14:47:26.637855477 +0100
@@ -1791,6 +1791,24 @@ rtl_tidy_fallthru_edge (edge e)
&& (any_uncondjump_p (q)
|| single_succ_p (b)))
{
+ rtx label;
+ rtx_jump_table_data *table;
+
+ if (tablejump_p (q, &label, &table))
+ {
+ /* The label is likely mentioned in some instruction before
+ the tablejump and might not be DCEd, so turn it into
+ a note instead and move before the tablejump that is going to
+ be deleted. */
+ const char *name = LABEL_NAME (label);
+ PUT_CODE (label, NOTE);
+ NOTE_KIND (label) = NOTE_INSN_DELETED_LABEL;
+ NOTE_DELETED_LABEL_NAME (label) = name;
+ rtx_insn *lab = safe_as_a <rtx_insn *> (label);
+ reorder_insns (lab, lab, PREV_INSN (q));
+ delete_insn (table);
+ }
+
#ifdef HAVE_cc0
/* If this was a conditional jump, we need to also delete
the insn that set cc0. */
--- gcc/testsuite/gcc.dg/pr64536.c.jj 2015-01-09 13:55:53.035267213 +0100
+++ gcc/testsuite/gcc.dg/pr64536.c 2015-01-09 13:55:53.035267213 +0100
@@ -0,0 +1,67 @@
+/* PR rtl-optimization/64536 */
+/* { dg-do link } */
+/* { dg-options "-O2" } */
+/* { dg-additional-options "-fPIC" { target fpic } } */
+
+struct S { long q; } *h;
+long a, b, g, j, k, *c, *d, *e, *f, *i;
+long *baz (void)
+{
+ asm volatile ("" : : : "memory");
+ return e;
+}
+
+void
+bar (int x)
+{
+ int y;
+ for (y = 0; y < x; y++)
+ {
+ switch (b)
+ {
+ case 0:
+ case 2:
+ a++;
+ break;
+ case 3:
+ a++;
+ break;
+ case 1:
+ a++;
+ }
+ if (d)
+ {
+ f = baz ();
+ g = k++;
+ if (&h->q)
+ {
+ j = *f;
+ h->q = *f;
+ }
+ else
+ i = (long *) (h->q = *f);
+ *c++ = (long) f;
+ e += 6;
+ }
+ else
+ {
+ f = baz ();
+ g = k++;
+ if (&h->q)
+ {
+ j = *f;
+ h->q = *f;
+ }
+ else
+ i = (long *) (h->q = *f);
+ *c++ = (long) f;
+ e += 6;
+ }
+ }
+}
+
+int
+main ()
+{
+ return 0;
+}
Jakub
