Tail-calling on the ARM

[Richard Earnshaw]

This patch uses the new mechanism to support tail-calling on the ARM (but 
not for thumb).  It replaces the old code that relied on peepholes and 
worked in much fewer cases.

It also fixes a bug in the is_thumb attribute, which caused it to be 
always enabled.

R.


2000-05-06  Richard Earnshaw (reanrsha@arm.com)

	Use new tail-calling mechanism on ARM.
	* arm.md (sibcall, sibcall_value): New expands.
	(sibcall_insn, sibcall_value_insn, sibcall_epilogue): New insns.
	(tailcalling peepholes): Delete.
	(push_multi): Simplify.
	* arm.c (lr_save_eliminated): Delete definition.
	(pattern_really_clobbers_lr, function_really_clobbers_lr): Delete.
	(output_return_instruction): Remove checks on lr_save_eliminated.
	(output_arm_prologue): Remove old tail-calling code.
	(arm_output_epilogue): New parameter, really_return.  All callers
	changed.  Handle tail-calling epilogues.
	* arm.h (lr_save_eliminated): Delete declaration.
	(frame_pointer_needed): Delete declaration.
	* arm-protos.h (arm_output_epilogue): Adjust prototype.

	* arm.md (is_thumb): Examine symbol thumb_code, not expression
	TARGET_ARM.
	* arm.c (thumb_code): Define it.
	(arm_override_options): Set it.
	* arm.h (thumb_code): Declare it.