reverting patch to improve equiv cost calculation

reverting patch to improve equiv cost calculation

[Vladimir Makarov]

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I've got a lot of complaints about my recent patch to improve equiv cost 
calculation.  So I am reverting the patch.

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commit 8552dcd8e4448c02fe230662093756b75dd94399
Author: Vladimir N. Makarov <vmakarov@redhat.com>
Date:   Thu Sep 28 11:53:51 2023 -0400

    Revert "[RA]: Improve cost calculation of pseudos with equivalences"
    
    This reverts commit 3c834d85f2ec42c60995c2b678196a06cb744959.
    
    Although the patch improves x86-64 specfp2007, it also results in
    performance and code size regression on different targets and
    new GCC testsuite failures on tests expecting a specific output.

diff --git a/gcc/ira-costs.cc b/gcc/ira-costs.cc
index 8c93ace5094..d9e700e8947 100644
--- a/gcc/ira-costs.cc
+++ b/gcc/ira-costs.cc
@@ -1947,8 +1947,15 @@ find_costs_and_classes (FILE *dump_file)
 	    }
 	  if (i >= first_moveable_pseudo && i < last_moveable_pseudo)
 	    i_mem_cost = 0;
-	  else
-	    i_mem_cost -= equiv_savings;
+	  else if (equiv_savings < 0)
+	    i_mem_cost = -equiv_savings;
+	  else if (equiv_savings > 0)
+	    {
+	      i_mem_cost = 0;
+	      for (k = cost_classes_ptr->num - 1; k >= 0; k--)
+		i_costs[k] += equiv_savings;
+	    }
+
 	  best_cost = (1 << (HOST_BITS_PER_INT - 2)) - 1;
 	  best = ALL_REGS;
 	  alt_class = NO_REGS;