On 16/11/15 13:33, Richard Biener wrote:
On Mon, Nov 16, 2015 at 12:43 PM, Andre Vieira
<andre.simoesdiasvie...@arm.com> wrote:
On 13/11/15 10:34, Richard Biener wrote:
On Thu, Nov 12, 2015 at 4:07 PM, Andre Vieira
<andre.simoesdiasvie...@arm.com> wrote:
Hi,
This patch changes this testcase to make sure LTO will not optimize
away
the assignment of the local array to a global variable which was
introduced
to make sure stack space was made available for the test to work.
This is correct because LTO is supposed to optimize this global away
as at
link time it knows this global will never be read. By adding a read of
the
global, LTO will no longer optimize it away.
But that's only because we can't see that bar doesn't clobber it, else
we would optimize away the check and get here again. Much better
to mark 'dummy' with __attribute__((used)) and go away with 'g' entirely.
Richard.
Tested by running regressions for this testcase for various ARM
targets.
Is this OK to commit?
Thanks,
Andre Vieira
gcc/testsuite/ChangeLog:
2015-11-06 Andre Vieira <andre.simoesdiasvie...@arm.com>
* gcc.dg/torture/stackalign/builtin-return-1.c: Added read
to global such that a write is not optimized away by LTO.
Hi Richard,
That would be great but __attribute__ ((used)) can only be used for static
variables and making dummy static would defeat the purpose here.
I see. What about volatile?
Cheers,
Andre
Yeh a 'volatile char dummy[64];' with a read afterwards leads to the
stack still being reserved after LTO and we won't need the global variable.
If you prefer that solution Ill respin the patch.
Cheers,
Andre
