[RA]: Modfify cost calculation for dealing with equivalences

RISCV target developers reported that pseudos with equivalence used in
a loop can be spilled.  Simple changes of heuristics of cost
calculation of pseudos with equivalence or even ignoring equivalences
resulted in numerous testsuite failures on different targets or worse
spec2017 performance.  This patch implements more sophisticated cost
calculations of pseudos with equivalences.  The patch does not change
RA behaviour for targets still using the old reload pass instead of
LRA.  The patch solves the reported problem and improves x86-64
specint2017 a bit (specfp2017 performance stays the same).  The patch
takes into account how the equivalence will be used: will it be
integrated into the user insns or require an input reload insn.  It
requires additional pass over insns.  To compensate RA slow down, the
patch removes a pass over insns in the reload pass used by IRA before.
This also decouples IRA from reload more and will help to remove the
reload pass in the future if it ever happens.

gcc/ChangeLog:

	* dwarf2out.cc (reg_loc_descriptor): Use lra_eliminate_regs when
	LRA is used.
	* ira-costs.cc: Include regset.h.
	(equiv_can_be_consumed_p, get_equiv_regno, calculate_equiv_gains):
	New functions.
	(find_costs_and_classes): Call calculate_equiv_gains and redefine
	mem_cost of pseudos with equivs when LRA is used.
	* var-tracking.cc: Include ira.h and lra.h.
	(vt_initialize): Use lra_eliminate_regs when LRA is used.

1 files changed, 3 insertions, 1 deletions

diff --git a/gcc/dwarf2out.cc b/gcc/dwarf2out.cc
index 0ea73bf..1e0cec6 100644
--- a/gcc/dwarf2out.cc
+++ b/gcc/dwarf2out.cc
@@ -14311,7 +14311,9 @@ reg_loc_descriptor (rtx rtl, enum var_init_status initialized)
      argument pointer and soft frame pointer rtx's.
      Use DW_OP_fbreg offset DW_OP_stack_value in this case.  */
   if ((rtl == arg_pointer_rtx || rtl == frame_pointer_rtx)
-      && eliminate_regs (rtl, VOIDmode, NULL_RTX) != rtl)
+      && (ira_use_lra_p
+	  ? lra_eliminate_regs (rtl, VOIDmode, NULL_RTX)
+	  : eliminate_regs (rtl, VOIDmode, NULL_RTX)) != rtl)
     {
       dw_loc_descr_ref result = NULL;