* i386.c (ix86_output_main_function_alignment_hack): New function.
	(TARGET_ASM_FUNCTION_PROLOGUE): Default to it.

	* flow.c (mark_dfs_back_edges): Move from loop_p ; mark back
	edges by EDGE_DFS_BACK flag.
	(dump_edge_info): Add dfs_back flag.
	* basic-block.h (EDGE_DFS_BACK): New constant.
	(mark_dfs_back_edges): Declare.
	* alias.c (loop_p): Remove.
	(mark_constant_function): Use mark_dfs_back_edges.

	* reg-stack.c (block_info_def): Add predecesors counter and stack_out.
	(reg_to_stack): Call mark_dfs_back_edges; count the predecesors.
	(compensate_edge): Break out from ...
	(convert_regs_1): ... here; do smart choosing of stack_out to copy.
	(convert_regs_2): Set block_done once block is really done;
	Do updating of the predecesors counts.

	* toplev.c (rest_of_compilation): Recompute block_for_insn
	before post-reload cfg_cleanup.
	* function.c (thread_prologue_epilogue_insns):
	Call set_block_for_new_insns when emitting prologue directly.

From-SVN: r44486