Fix reload1.c warning for some targets

[Richard Sandiford]

Building some targets results in a warning about orig_dup[i] potentially
being used uninitialised.  I think the warning is fair, since it isn't
obvious that the reog_data-based loop bound remains unchanged between:

  for (i = 0; i < recog_data.n_dups; i++)
    orig_dup[i] = *recog_data.dup_loc[i];

and:

  for (i = 0; i < recog_data.n_dups; i++)
    *recog_data.dup_loc[i] = orig_dup[i];

Tested on x86_64-linux-gnu.  OK to install?

Thanks,
Richard

gcc/
        * reload1.c (elimination_costs_in_insn): Make it obvious to the
        compiler that the n_dups and n_operands loop bounds are invariant.

diff --git a/gcc/reload1.c b/gcc/reload1.c
index ce06e06..ad243e3 100644
--- a/gcc/reload1.c
+++ b/gcc/reload1.c
@@ -3708,10 +3708,12 @@ elimination_costs_in_insn (rtx_insn *insn)
   /* Eliminate all eliminable registers occurring in operands that
      can be handled by reload.  */
   extract_insn (insn);
-  for (i = 0; i < recog_data.n_dups; i++)
+  int n_dups = recog_data.n_dups;
+  for (i = 0; i < n_dups; i++)
     orig_dup[i] = *recog_data.dup_loc[i];
 
-  for (i = 0; i < recog_data.n_operands; i++)
+  int n_operands = recog_data.n_operands;
+  for (i = 0; i < n_operands; i++)
     {
       orig_operand[i] = recog_data.operand[i];
 
@@ -3756,7 +3758,7 @@ elimination_costs_in_insn (rtx_insn *insn)
        }
     }
 
-  for (i = 0; i < recog_data.n_dups; i++)
+  for (i = 0; i < n_dups; i++)
     *recog_data.dup_loc[i]
       = *recog_data.operand_loc[(int) recog_data.dup_num[i]];
 
@@ -3764,9 +3766,9 @@ elimination_costs_in_insn (rtx_insn *insn)
   check_eliminable_occurrences (old_body);
 
   /* Restore the old body.  */
-  for (i = 0; i < recog_data.n_operands; i++)
+  for (i = 0; i < n_operands; i++)
     *recog_data.operand_loc[i] = orig_operand[i];
-  for (i = 0; i < recog_data.n_dups; i++)
+  for (i = 0; i < n_dups; i++)
     *recog_data.dup_loc[i] = orig_dup[i];
 
   /* Update all elimination pairs to reflect the status after the current