[PATCH] Only use NO_REGS in cost calculation when !hard_regno_mode_ok for GENERAL_REGS and mode.

[liuhongt <hongtao.liu@intel.com>]

r14-172-g0368d169492017 replaces GENERAL_REGS with NO_REGS in cost
calculation when the preferred register class are not known yet.
It regressed powerpc PR109610 and PR109858, it looks too aggressive to use
NO_REGS when mode can be allocated with GENERAL_REGS.
The patch takes a step back, still use GENERAL_REGS when
hard_regno_mode_ok for mode and GENERAL_REGS, otherwise uses NO_REGS.
Kewen confirmed the patch fixed PR109858, I vefiried it also fixed PR109610.

Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
No big performance impact for SPEC2017 on icelake server.
Ok for trunk?

gcc/ChangeLog:

	* ira-costs.cc (scan_one_insn): Only use NO_REGS in cost
	calculation when !hard_regno_mode_ok for GENERAL_REGS and
	mode, otherwise still use GENERAL_REGS.
---
 gcc/ira-costs.cc | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/gcc/ira-costs.cc b/gcc/ira-costs.cc
index d2a801ab9b0..ae8304ff938 100644
--- a/gcc/ira-costs.cc
+++ b/gcc/ira-costs.cc
@@ -1572,12 +1572,16 @@ scan_one_insn (rtx_insn *insn)
       && (! ira_use_lra_p || ! pic_offset_table_rtx
 	  || ! contains_symbol_ref_p (XEXP (note, 0))))
     {
-      /* Costs for NO_REGS are used in cost calculation on the
-	 1st pass when the preferred register classes are not
-	 known yet.  In this case we take the best scenario.  */
-      enum reg_class cl = NO_REGS;
+      enum reg_class cl = GENERAL_REGS;
       rtx reg = SET_DEST (set);
       int num = COST_INDEX (REGNO (reg));
+      /* Costs for NO_REGS are used in cost calculation on the
+	 1st pass when the preferred register classes are not
+	 known yet.  In this case we take the best scenario when
+	 mode can't be put into GENERAL_REGS.  */
+      if (!targetm.hard_regno_mode_ok (ira_class_hard_regs[cl][0],
+				       GET_MODE (reg)))
+	cl = NO_REGS;
 
       COSTS (costs, num)->mem_cost
 	-= ira_memory_move_cost[GET_MODE (reg)][cl][1] * frequency;
-- 
2.39.1.388.g2fc9e9ca3c