On Tue, Mar 05, 2013 at 11:03:13PM +0100, Jakub Jelinek wrote:
> > ifcvt.c tests only small_register_classes_for_mode_p in the other places,
> > so
> > do you really need class_likely_spilled_p here?
>
> I guess I don't. I've grepped for small_register_classes_for_mode_p and
> didn't see
> anything in i386, so I figured out that it would be using a default (which
> is false). But apparently it uses hook_bool_mode_true, so it is a superset
> of class_likely_spilled_p, guess I can leave that out.
Here is what I've actually committed (I've also removed the
!reload_completed &&, because noce_process_if_block is only called for
!!reload_completed (the only caller asserts it)).
2013-03-05 Jakub Jelinek <ja...@redhat.com>
PR rtl-optimization/56484
* ifcvt.c (noce_process_if_block): If else_bb is NULL, avoid extending
lifetimes of hard registers on small register class machines.
* gcc.c-torture/compile/pr56484.c: New test.
--- gcc/ifcvt.c.jj 2013-03-05 15:12:15.284564443 +0100
+++ gcc/ifcvt.c 2013-03-05 23:11:25.751625601 +0100
@@ -2491,6 +2491,12 @@ noce_process_if_block (struct noce_if_in
|| ! noce_operand_ok (SET_SRC (set_b))
|| reg_overlap_mentioned_p (x, SET_SRC (set_b))
|| modified_between_p (SET_SRC (set_b), insn_b, jump)
+ /* Avoid extending the lifetime of hard registers on small
+ register class machines. */
+ || (REG_P (SET_SRC (set_b))
+ && HARD_REGISTER_P (SET_SRC (set_b))
+ && targetm.small_register_classes_for_mode_p
+ (GET_MODE (SET_SRC (set_b))))
/* Likewise with X. In particular this can happen when
noce_get_condition looks farther back in the instruction
stream than one might expect. */
--- gcc/testsuite/gcc.c-torture/compile/pr56484.c.jj 2013-03-05
16:57:50.416961638 +0100
+++ gcc/testsuite/gcc.c-torture/compile/pr56484.c 2013-03-05
16:57:50.417961672 +0100
@@ -0,0 +1,17 @@
+/* PR rtl-optimization/56484 */
+
+unsigned char b[4096];
+int bar (void);
+
+int
+foo (void)
+{
+ int a = 0;
+ while (bar ())
+ {
+ int c = bar ();
+ a = a < 0 ? a : c;
+ __builtin_memset (b, 0, sizeof b);
+ }
+ return a;
+}
Jakub
