* rtl.h (truncated_to_mode): Declare it.
	(struct rtl_hooks): Add reg_truncated_to_mode hook.
	* rtlhooks-def.h (RTL_HOOKS_REG_TRUNCATED_TO_MODE): New macro.
	(RTL_HOOKS_INITIALIZER): Include it.
	* rtlhooks.c (reg_truncated_to_mode_general): New function.
	* combine.c (RTL_HOOKS_REG_TRUNCATED_TO_MODE): Override to
	reg_truncated_to_mode.
	* rtlanal.c (truncated_to_mode): Define it.
	* simplify-rtx.c (simplify_unary_operation_1): Use it.

Co-Authored-By: Adam Nemet <anemet@caviumnetworks.com>

From-SVN: r111573