On 01/11/14 02:21, Bin.Cheng wrote:
On Sat, Jan 11, 2014 at 5:07 PM, Jakub Jelinek <ja...@redhat.com> wrote:
On Sat, Jan 11, 2014 at 05:02:26PM +0800, Bin.Cheng wrote:
I reduced the case and attached ivopt dumps with/without the patch.
It seems the patch is doing right thing and choosing better
candidates, most likely it reveals an existing bug.
I am looking into this issue, in the meantime, I am wondering should I
apply the patch and file a PR for it, or apply the patch after root
causing it?
Sounds like PR59743 which should be already fixed.
Yes, it is. I just did the test against trunk exactly before Jeff's fix.
Then I will apply the patch to trunk.
And an additional question: Are these uses before definition always
caused by uninitialized use in GCC?
In general, no.
Consider a loop where an object's use is guarded (say it only gets used
on the 2nd and later iterations) and the set is unguarded. ISTM that
the reaching def would be from a later insn in the loop.
jeff
