rs6000.md (bswaphi2_reg): On ISA 3.0 systems, enable generating XXBRH if the value is in a vector register.

[gcc]
2017-11-10  Michael Meissner  <meissner@linux.vnet.ibm.com>

	* config/rs6000/rs6000.md (bswaphi2_reg): On ISA 3.0 systems,
	enable generating XXBRH if the value is in a vector register.
	(bswapsi2_reg): On ISA 3.0 systems, enable generating XXBRW if the
	value is in a vector register.
	(bswapdi2_reg): On ISA 3.0 systems, always use XXBRD to do
	register to register bswap64's instead of doing the GPR sequence
	used on previous machines.
	(bswapdi2_xxbrd): New insn.
	(bswapdi2_reg): Disallow on ISA 3.0.
	(register to register bswap64 splitter): Do not split the insn on
	ISA 3.0 systems that use XXBRD.

[gcc/testsuite]
2017-11-10  Michael Meissner  <meissner@linux.vnet.ibm.com>

	* gcc.target/powerpc/p9-xxbr-3.c: New test.

From-SVN: r254643