* config/rs6000/rs6000.c (function_arg_advance): For 32-bit ELF ABI,
	expand on the comment about _Decimal128 arguments and check the
	integer result of the modulus operation; for 64-bit ELF ABI, ensure
	that _Decimal128 argument uses even/odd register pair.
	(function_arg): For 32-bit ELF ABI, expand on the comment about
	_Decimal128 arguments and check the integer result of the modulus
	operation; for 64-bit ELF ABI, ensure that _Decimal128 argument
	uses even/odd register pair.
testsuite/
	* gcc.target/powerpc/ppc32-abi-dfp-1.c: New test.
	* gcc.target/powerpc/ppc64-abi-dfp-1.c: New test.

From-SVN: r124116