[ARC] Update EH code.

[ARC] Update EH code.

Our ABI says the blink is pushed first on stack followed by an unknown
number of register saves, and finally by fp.  Hence we cannot use the
EH_RETURN_ADDRESS macro as the stack is not finalized at that moment.
The alternative is to use the eh_return pattern and to initialize all
the bits after register allocation when the stack layout is finalized.

gcc/
xxxx-xx-xx  Claudiu Zissulescu  <claziss@synopsys.com>

	* config/arc/arc.c (arc_eh_return_address_location): Repurpose it
	to fit the eh_return pattern.
	* config/arc/arc.md (eh_return): Define.
	(VUNSPEC_ARC_EH_RETURN): Likewise.
	* config/arc/arc-protos.h (arc_eh_return_address_location): Match
	new implementation.
	* config/arc/arc.h (EH_RETURN_HANDLER_RTX): Remove it.

testsuite/
xxxx-xx-xx  Claudiu Zissulescu  <claziss@synopsys.com>

	* gcc.target/arc/builtin_eh.c: New test.

From-SVN: r266066