Backport two changes to the 2.95 branch

From-SVN: r37891

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 1456bc36b982eefbee0f608a745cb53f64cda73b..96efcf396431d057ec079814a208f9330ed56dfd 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,14 @@
 2000-11-30  Bernd Schmidt  <bernds@redhat.co.uk>
 
+       2000-09-01  Jim Wilson  <wilson@cygnus.com>
+       * loop.c (check_final_value): Check for biv use before checking for
+       giv use.  Check for both biv and giv uses.  Always set last_giv_use
+       if there is a giv use.
+
+       2000-09-29  Franz Sirl  <Franz.Sirl-kernel@lauterbach.com>
+       * loop.c (check_final_value): A GIV is not replaceable if used
+       before set.
+
        Sun Oct 10 13:28:48 1999  Bernd Schmidt  <bernds@redhat.co.uk>
        * loop.c (find_and_verify_loops): When looking for a BARRIER, don't
        use one before a jump table.

diff --git a/gcc/loop.c b/gcc/loop.c
index 0b121cb918c5d80150e15a62ba2ad17e2e6b82e2..3991a71fdb8b316e486700661c437063aa8f3385 100644 (file)
--- a/gcc/loop.c
+++ b/gcc/loop.c
@@ -5692,6 +5692,7 @@ check_final_value (v, loop_start, loop_end, n_iterations)
         or all uses follow that insn in the same basic block),
      - its final value can be calculated (this condition is different
        than the one above in record_giv)
+     - it's not used before it's set
      - no assignments to the biv occur during the giv's lifetime.  */
 
 #if 0
@@ -5703,7 +5704,7 @@ check_final_value (v, loop_start, loop_end, n_iterations)
   if ((final_value = final_giv_value (v, loop_start, loop_end, n_iterations))
       && (v->always_computable || last_use_this_basic_block (v->dest_reg, v->insn)))
     {
-      int biv_increment_seen = 0;
+      int biv_increment_seen = 0, before_giv_insn = 0;
       rtx p = v->insn;
       rtx last_giv_use;
 
@@ -5733,26 +5734,35 @@ check_final_value (v, loop_start, loop_end, n_iterations)
        {
          p = NEXT_INSN (p);
          if (p == loop_end)
-           p = NEXT_INSN (loop_start);
+           {
+             before_giv_insn = 1;
+             p = NEXT_INSN (loop_start);
+           }
          if (p == v->insn)
            break;
 
          if (GET_CODE (p) == INSN || GET_CODE (p) == JUMP_INSN
              || GET_CODE (p) == CALL_INSN)
            {
-             if (biv_increment_seen)
+             /* It is possible for the BIV increment to use the GIV if we
+                have a cycle.  Thus we must be sure to check each insn for
+                both BIV and GIV uses, and we must check for BIV uses
+                first.  */
+
+             if (! biv_increment_seen
+                 && reg_set_p (v->src_reg, PATTERN (p)))
+               biv_increment_seen = 1;
+
+             if (reg_mentioned_p (v->dest_reg, PATTERN (p)))
                {
-                 if (reg_mentioned_p (v->dest_reg, PATTERN (p)))
+                 if (biv_increment_seen || before_giv_insn)
                    {
                      v->replaceable = 0;
                      v->not_replaceable = 1;
                      break;
                    }
+                 last_giv_use = p;
                }
-             else if (reg_set_p (v->src_reg, PATTERN (p)))
-               biv_increment_seen = 1;
-             else if (reg_mentioned_p (v->dest_reg, PATTERN (p)))
-               last_giv_use = p;
            }
        }