ira: Add a target hook for callee-saved register cost scale

commit 3b9b8d6c
Author: Surya Kumari Jangala <jskumari@linux.ibm.com>
Date:   Tue Jun 25 08:37:49 2024 -0500

    ira: Scale save/restore costs of callee save registers with block frequency

scales the cost of saving/restoring a callee-save hard register in epilogue
and prologue with the entry block frequency, which, if not optimizing for
size, is 10000, for all targets.  As the result, callee-saved registers
may not be used to preserve local variable values across calls on some
targets, like x86.  Add a target hook for the callee-saved register cost
scale in epilogue and prologue used by IRA.  The default version of this
target hook returns 1 if optimizing for size, otherwise returns the entry
block frequency.  Add an x86 version of this target hook to restore the
old behavior prior to the above commit.

	PR rtl-optimization/111673
	PR rtl-optimization/115932
	PR rtl-optimization/116028
	PR rtl-optimization/117081
	PR rtl-optimization/117082
	PR rtl-optimization/118497
	* ira-color.cc (assign_hard_reg): Call the target hook for the
	callee-saved register cost scale in epilogue and prologue.
	* target.def (ira_callee_saved_register_cost_scale): New target
	hook.
	* targhooks.cc (default_ira_callee_saved_register_cost_scale):
	New.
	* targhooks.h (default_ira_callee_saved_register_cost_scale):
	Likewise.
	* config/i386/i386.cc (ix86_ira_callee_saved_register_cost_scale):
	New.
	(TARGET_IRA_CALLEE_SAVED_REGISTER_COST_SCALE): Likewise.
	* doc/tm.texi: Regenerated.
	* doc/tm.texi.in (TARGET_IRA_CALLEE_SAVED_REGISTER_COST_SCALE):
	New.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>