On Mon, Nov 16, 2015 at 3:08 PM, Andre Vieira <andre.simoesdiasvie...@arm.com> wrote: > 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.
Yes please. Richard. > Cheers, > Andre >
