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 >
