re PR rtl-optimization/57662 (ICE: SIGSEGV in code_motion_process_successors with -fschedule-insns2 -fselective-scheduling2)

PR rtl-optimization/57662

gcc/
	* sel-sched.c (code_motion_process_successors): When the current insn
	is removed after the recursive traversal, break from the loop.
	Add comments and debug printouts.

testsuite/

	* gcc.dg/pr57662.c: New test.

From-SVN: r201728