[PATCH] testsuite: Prevent unrolling of main in LTO test [PR116683]

[Alex Coplan]

Hi,

In r15-3585-g9759f6299d9633cabac540e5c893341c708093ac I added a test which
started failing on PowerPC.  The test checks that we unroll exactly one loop
three times with the following:

// { dg-final { scan-ltrans-rtl-dump-times "Unrolled loop 3 times" 1 
"loop2_unroll" } }

which passes on most targets.  However, on PowerPC, the loop in main
gets unrolled too, causing the scan-ltrans-rtl-dump-times check to fail
as the statement now appears twice in the dump.  I think the extra
unrolling is due to different unrolling heuristics in the rs6000 port.

This patch therefore explicitly tries to block the unrolling in main with an
appropriate #pragma.

I've checked that the test now passes on power (on cfarm29) and aarch64.  I also
checked that reverting the lto-streamer-{in,out}.cc changes still causes the
test to fail (on aarch64).

OK for trunk?

Thanks,
Alex

gcc/testsuite/ChangeLog:

        PR testsuite/116683
        * g++.dg/ext/pragma-unroll-lambda-lto.C (main): Add #pragma to
        prevent unrolling of the setup loop.

diff --git a/gcc/testsuite/g++.dg/ext/pragma-unroll-lambda-lto.C 
b/gcc/testsuite/g++.dg/ext/pragma-unroll-lambda-lto.C
index 64cdf90f34d..20cbd2d15cf 100644
--- a/gcc/testsuite/g++.dg/ext/pragma-unroll-lambda-lto.C
+++ b/gcc/testsuite/g++.dg/ext/pragma-unroll-lambda-lto.C
@@ -24,6 +24,7 @@ short *use_find(short *p)
 int main(void)
 {
   short a[1024];
+#pragma GCC unroll 0
   for (int i = 0; i < 1024; i++)
     a[i] = rand ();