openmp: Fix placement of 2nd+ preparation statement for PHIs in simd clone lowering...

openmp: Fix placement of 2nd+ preparation statement for PHIs in simd clone lowering [PR95108]

For normal stmts, preparation statements are inserted before the stmt, so if we need multiple,
they are in the correct order, but for PHIs we emit them after labels in the entry successor
bb, and we used to emit them in the reverse order that way.

2020-05-14  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/95108
	* omp-simd-clone.c (struct modify_stmt_info): Add after_stmt member.
	(ipa_simd_modify_stmt_ops): For PHIs, only add before first stmt in
	entry block if info->after_stmt is NULL, otherwise add after that stmt
	and update it after adding each stmt.
	(ipa_simd_modify_function_body): Initialize info.after_stmt.

	* gcc.dg/gomp/pr95108.c: New test.

(cherry picked from commit d0fb9ffc1b8f3b86bbdf0e915cec2136141b329b)