On 09/23/14 10:01, Steven Bosscher wrote:
On Fri, Sep 19, 2014 at 10:03 PM, Jeff Law <l...@redhat.com> wrote:
On 09/19/14 13:36, Ilya Enkovich wrote:
Hi,
During my work on enabling pseudo PIC register I've found that cfg cleaunp
may remove lables with LABEL_PRESERVE_P set to 1. In my case I generated
SET_RIP during expand pass and cfg cleanup removed label it used as an
operand. Below is a patch that fixes it. It is not actually required for
our latest PIC related patch but still seems to make sense.
Bootstrapped and tested on linux-x86_64.
Thanks,
Ilya
--
2014-09-19 Ilya Enkovich <ilya.enkov...@intel.com>
* cfgcleanup.c (try_optimize_cfg): Do not remove label
with LABEL_PRESERVE_P flag set.
OK. Please install.
Note for those not following the x86 32 bit PIC register discussion, I asked
Ilya to submit this separately. It was something an earlier version of his
patch triggered and it stood out as something that ought to be fixed
regardless of the final form of the PIC register changes that are in
progress.
Jeff,
Are you sure this patch is necessary, and is not just papering over
another problem? In the past, all cases I've seen where labels were
removed inadvertently were caused by incorrect reference counting or
missing REG_LABEL_* notes.
Did the label use count drop to zero? Is there a REG_LABEL_TARGET note
for the label operand?
The way it was described to me is, yes, the label count dropped to zero.
In simplest terms, it was a single use label that was marked with
LABEL_PRESERVE_P. The combiner removed the last reference, then
cfgcleanup came along and *boom*.
It was with some ongoing development work that's going in a slight
different direction, so we don't have a testcase to include.
jeff
