backport: rs6000.c (rtx_is_swappable_p): Commentary adjustments.

backport: rs6000.c (rtx_is_swappable_p): Commentary adjustments.

[gcc]

2015-04-24  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>

	Backport from mainline r222351
	2015-04-22  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>

	* config/rs6000/rs6000.c (rtx_is_swappable_p): Commentary
	adjustments.
	(insn_is_swappable_p): Return 1 for a convert from double to
	single precision when all of its uses are splats of BE element
	zero.

[gcc/testsuite]

2015-04-24  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>

	Backport from mainline r222351
	2015-04-22  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>

	* gcc.target/powerpc/swaps-p8-18.c: New test.

From-SVN: r222427