[PATCH] Adjust param_vect_max_version_for_alias_checks

[PATCH] Adjust param_vect_max_version_for_alias_checks

This patch sets param_vect_max_version_for_alias_checks to 15.
This was causing GCC to miss vectorization opportunities for an application,
making it slower than LLVM by about ~14%.

Original default of 10 itself is arbitary. Given that, GCC's vectoriser does
consideres cost of alias checks, increasing this param is reasonable.

In this case we need a value of at teast 11 whereas the current
default is 10.

gcc/ChangeLog:

	* params.opt: Adjust param_vect_max_version_for_alias_checks

gcc/testsuite/ChangeLog:

	* g++.dg/alias-checks.C: New test.

Signed-off-by: Kugan Vivekanandarajah <kvivekananda@nvidia.com>