[pushed][LRA]: When assigning stack slots to pseudos previously assigned to fp consider other spilled pseudos

[Vladimir Makarov <vmakarov@redhat.com>]

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The following patch fixes a problem with allocating the same stack slots 
to conflicting pseudos.  The problem exists only for AVR LRA port.

The patch was successfully bootstrapped and tested on x86-64 and aarch64.


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commit c024867d1aa9d465e0236fc9d45d8e1d4bb6bd30
Author: Vladimir N. Makarov <vmakarov@redhat.com>
Date:   Thu Aug 17 11:57:45 2023 -0400

    [LRA]: When assigning stack slots to pseudos previously assigned to fp consider other spilled pseudos
    
    The previous LRA patch can assign slot of conflicting pseudos to
    pseudos spilled after prohibiting fp->sp elimination.  This patch
    fixes this problem.
    
    gcc/ChangeLog:
    
            * lra-spills.cc (assign_stack_slot_num_and_sort_pseudos): Moving
            slots_num initialization from here ...
            (lra_spill): ... to here before the 1st call of
            assign_stack_slot_num_and_sort_pseudos.  Add the 2nd call after
            fp->sp elimination.

diff --git a/gcc/lra-spills.cc b/gcc/lra-spills.cc
index 7e1d35b5e4e..a663a1931e3 100644
--- a/gcc/lra-spills.cc
+++ b/gcc/lra-spills.cc
@@ -363,7 +363,6 @@ assign_stack_slot_num_and_sort_pseudos (int *pseudo_regnos, int n)
 {
   int i, j, regno;
 
-  slots_num = 0;
   /* Assign stack slot numbers to spilled pseudos, use smaller numbers
      for most frequently used pseudos.	*/
   for (i = 0; i < n; i++)
@@ -628,6 +627,7 @@ lra_spill (void)
   /* Sort regnos according their usage frequencies.  */
   qsort (pseudo_regnos, n, sizeof (int), regno_freq_compare);
   n = assign_spill_hard_regs (pseudo_regnos, n);
+  slots_num = 0;
   assign_stack_slot_num_and_sort_pseudos (pseudo_regnos, n);
   for (i = 0; i < n; i++)
     if (pseudo_slots[pseudo_regnos[i]].mem == NULL_RTX)
@@ -635,6 +635,7 @@ lra_spill (void)
   if ((n2 = lra_update_fp2sp_elimination (pseudo_regnos)) > 0)
     {
       /* Assign stack slots to spilled pseudos assigned to fp.  */
+      assign_stack_slot_num_and_sort_pseudos (pseudo_regnos, n2);
       for (i = 0; i < n2; i++)
 	if (pseudo_slots[pseudo_regnos[i]].mem == NULL_RTX)
 	  assign_mem_slot (pseudo_regnos[i]);