re PR target/16532 (Inefficient jump to epilogue)

re PR target/16532 (Inefficient jump to epilogue)

	PR target/16532
	* config/sparc/sparc.c (struct machine_function): New field
	'leaf_function_p' and 'prologue_data_valid_p'.
	(sparc_leaf_function_p, sparc_prologue_data_valid_p): New macro
	to conveniently access the above fields.
	(TARGET_LATE_RTL_PROLOGUE_EPILOGUE): Delete.
	(eligible_for_return_delay): Use 'sparc_leaf_function_p' instead
	of the generic flavor 'current_function_uses_only_leaf_regs'.
	(eligible_for_sibcall_delay): Likewise.
	(sparc_expand_prologue): Compute 'sparc_leaf_function_p' and set
	'sparc_prologue_data_valid_p'.  Use 'sparc_leaf_function_p'.
	(sparc_asm_function_prologue): Add sanity check for the assumption
	made in 'sparc_expand_prologue'.  Use 'sparc_leaf_function_p'.
	(sparc_can_use_return_insn_p): New function.
	(sparc_expand_epilogue): Use 'sparc_leaf_function_p'.
	(output_restore): Likewise.
	(output_sibcall): Likewise.
	(sparc_output_mi_thunk): Likewise.
	* config/sparc/sparc-protos.h (sparc_can_use_return_insn_p): Declare.
	* config/sparc/sparc.md (return): New expander.

	* config/sparc/sparc.h (INITIAL_ELIMINATION_OFFSET): Minor tweak.

From-SVN: r88220