rs6000.md (floor<mode>2): Add support for IEEE 128-bit round to integer instructions.

[gcc]
2018-01-02  Michael Meissner  <meissner@linux.vnet.ibm.com>

	* config/rs6000/rs6000.md (floor<mode>2): Add support for IEEE
	128-bit round to integer instructions.
	(ceil<mode>2): Likewise.
	(btrunc<mode>2): Likewise.
	(round<mode>2): Likewise.

[gcc/testsuite]
2018-01-02  Michael Meissner  <meissner@linux.vnet.ibm.com>

	* gcc.target/powerpc/float128-hw2.c: Add tests for ceilf128,
	floorf128, truncf128, and roundf128.
	* gcc.target/powerpc/float128-hw5.c: New tests for _Float128
	optimizations added in match.pd.
	* gcc.target/powerpc/float128-hw6.c: Likewise.
	* gcc.target/powerpc/float128-hw7.c: Likewise.
	* gcc.target/powerpc/float128-hw8.c: Likewise.
	* gcc.target/powerpc/float128-hw9.c: Likewise.
	* gcc.target/powerpc/float128-hw10.c: Likewise.
	* gcc.target/powerpc/float128-hw11.c: Likewise.

From-SVN: r256118