Fix hppa miscompilation bug reported by Manfred Hollstein.

	* loop.c (check_dbra_loop): New locals jump, first_compare, and
	compare_and_branch.  Call get_condition to set first_compare.
	Set compare_and_branch to number of compare/branch instructions.
	Replace PREV_INSN (PREV_INSN (loop_end)) with first_compare.
	Replace '2' with compare_and_branch.

From-SVN: r19435

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index e0fb8aff874161b0155d83bd8de73c859eb1f5fb..1c1c09f39a6053a08e682fa8e2794d94d5e7b016 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+Mon Apr 27 18:36:28 1998  Jim Wilson  <wilson@cygnus.com>
+
+       * loop.c (check_dbra_loop): New locals jump, first_compare, and
+       compare_and_branch.  Call get_condition to set first_compare.
+       Set compare_and_branch to number of compare/branch instructions.
+       Replace PREV_INSN (PREV_INSN (loop_end)) with first_compare.
+       Replace '2' with compare_and_branch.
+
 Mon Apr 27 15:53:30 EDT 1998 Andrew MacLeod <amacleod@cygnus.com>
 
        * cplus-dem.c (demangle_qualified): Replace missing else.

diff --git a/gcc/loop.c b/gcc/loop.c
index 6b66484647b160a66e4d59f713e957a6a16f48b5..70ecfa8bf329775a5b4ddf393c4a8da35d35baf7 100644 (file)
--- a/gcc/loop.c
+++ b/gcc/loop.c
@@ -6094,14 +6094,28 @@ check_dbra_loop (loop_end, insn_count, loop_start)
   rtx comparison;
   rtx before_comparison;
   rtx p;
+  rtx jump;
+  rtx first_compare;
+  int compare_and_branch;
 
   /* If last insn is a conditional branch, and the insn before tests a
      register value, try to optimize it.  Otherwise, we can't do anything.  */
 
-  comparison = get_condition_for_loop (PREV_INSN (loop_end));
+  jump = PREV_INSN (loop_end);
+  comparison = get_condition_for_loop (jump);
   if (comparison == 0)
     return 0;
 
+  /* Try to compute whether the compare/branch at the loop end is one or
+     two instructions.  */
+  get_condition (jump, &first_compare);
+  if (first_compare == jump)
+    compare_and_branch = 1;
+  else if (first_compare == prev_nonnote_insn (jump))
+    compare_and_branch = 2;
+  else
+    return 0;
+
   /* Check all of the bivs to see if the compare uses one of them.
      Skip biv's set more than once because we can't guarantee that
      it will be zero on the last iteration.  Also skip if the biv is
@@ -6112,7 +6126,7 @@ check_dbra_loop (loop_end, insn_count, loop_start)
       if (bl->biv_count == 1
          && bl->biv->dest_reg == XEXP (comparison, 0)
          && ! reg_used_between_p (regno_reg_rtx[bl->regno], bl->biv->insn,
-                                  PREV_INSN (PREV_INSN (loop_end))))
+                                  first_compare))
        break;
     }
 
@@ -6253,7 +6267,7 @@ check_dbra_loop (loop_end, insn_count, loop_start)
          && reversible_mem_store
          && (no_use_except_counting
              || ((bl->giv_count + bl->biv_count + num_mem_sets
-                  + num_movables + 2 == insn_count)
+                  + num_movables + compare_and_branch == insn_count)
                  && (bl == loop_iv_list && bl->next == 0))))
        {
          rtx tem;
@@ -6345,8 +6359,7 @@ check_dbra_loop (loop_end, insn_count, loop_start)
 
              /* Emit an insn after the end of the loop to set the biv's
                 proper exit value if it is used anywhere outside the loop.  */
-             if ((REGNO_LAST_UID (bl->regno)
-                  != INSN_UID (PREV_INSN (PREV_INSN (loop_end))))
+             if ((REGNO_LAST_UID (bl->regno) != INSN_UID (first_compare))
                  || ! bl->init_insn
                  || REGNO_FIRST_UID (bl->regno) != INSN_UID (bl->init_insn))
                emit_insn_after (gen_move_insn (reg, final_value),
@@ -6354,7 +6367,8 @@ check_dbra_loop (loop_end, insn_count, loop_start)
 
              /* Delete compare/branch at end of loop.  */
              delete_insn (PREV_INSN (loop_end));
-             delete_insn (PREV_INSN (loop_end));
+             if (compare_and_branch == 2)
+               delete_insn (first_compare);
 
              /* Add new compare/branch insn at end of loop.  */
              start_sequence ();