* predict.c (expensive_function_p): New.
	* rtl.h (expensive_function_p): Declare.
	* i386.c (FAST_PROLOGUE_INSN_COUNT): New constant.
	(use_fast_prologue_epilogue): New static variable.
	(expand_prologue): Set it; emit short prologues if unset.
	(expand_epilogue): Likewise.

From-SVN: r45176