builtins.c (fold_builtin_bitop): New function to perform constant folding of ffs...

	* builtins.c (fold_builtin_bitop): New function to perform constant
	folding of ffs, clz, ctz, popcount and parity builtin functions
	and their long and long long variants (such as ffsl and ffsll).
	(fold_builtin): fold_builtin_bitop when appropriate.
	* simplify-rtx.c (simplify_unary_operation): Honor both
	CLZ_DEFINED_VALUE_AT_ZERO and CTZ_DEFINED_VALUE_AT_ZERO when
	evaluating clz and ctz at compile-time, for operands wider
	than HOST_WIDE_INT.

From-SVN: r70806