S/390: Add static OSC breaker if necessary.

S/390: Add static OSC breaker if necessary.

This patch adds a magic OSC (operand store compare) break instruction
which is necessary if a store is followed closely by a load with same
base+indx+displ while either base or index get modified in between.

The patch improves several SpecCPU testcases running on IBM z13.

gcc/testsuite/ChangeLog:

2016-10-28  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	* gcc.target/s390/oscbreak-1.c: New test.

gcc/ChangeLog:

2016-10-28  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	* config/s390/s390.c (s390_adjust_loop_scan_osc): New function.
	(s390_adjust_loops): New function.
	(s390_reorg): Invoke s390_adjust_loops.
	* config/s390/s390.md: (UNSPEC_OSC_BREAK): New constant.
	("osc_break"): New insn definition.

From-SVN: r241644