loop.c (check_dbra_loop): Update JUMP_LABEL field of jump insn when loop reversed.

	* loop.c (check_dbra_loop): Update JUMP_LABEL field of jump insn
	when loop reversed.
	* unroll.c (precondition_loop_p): Return loop_initial_value
	for initial_value instead of loop_iteration_var.

From-SVN: r23881

3 files changed, 25 insertions, 20 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 4118573..d066040 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+Thu Nov 26 17:49:29 1998  Michael Hayes  <m.hayes@elec.canterbury.ac.nz>
+
+	* loop.c (check_dbra_loop): Update JUMP_LABEL field of jump insn
+	when loop reversed.
+
+	* unroll.c (precondition_loop_p): Return loop_initial_value
+	for initial_value instead of loop_iteration_var.
+
 Thu Nov 26 17:15:38 1998  Michael Hayes  <m.hayes@elec.canterbury.ac.nz>
 
 	* config/c4x/c4x.md: Fix minor formatting problems.  Update docs.
diff --git a/gcc/loop.c b/gcc/loop.c
index b664e38..4fb5198 100644
--- a/gcc/loop.c
+++ b/gcc/loop.c
@@ -7107,16 +7107,18 @@ check_dbra_loop (loop_end, insn_count, loop_start)
 	      end_sequence ();
 	      emit_jump_insn_before (tem, loop_end);
 
+	      for (tem = PREV_INSN (loop_end);
+		   tem && GET_CODE (tem) != JUMP_INSN;
+		   tem = PREV_INSN (tem))
+		;
+
+	      if (tem)
+		JUMP_LABEL (tem) = XEXP (jump_label, 0);
+
 	      if (nonneg)
 		{
-		  for (tem = PREV_INSN (loop_end);
-		       tem && GET_CODE (tem) != JUMP_INSN;
-		       tem = PREV_INSN (tem))
-		    ;
 		  if (tem)
 		    {
-		      JUMP_LABEL (tem) = XEXP (jump_label, 0);
-
 		      /* Increment of LABEL_NUSES done above.  */
 		      /* Register is now always nonnegative,
 			 so add REG_NONNEG note to the branch.  */
diff --git a/gcc/unroll.c b/gcc/unroll.c
index 034fe52..9bf6a51 100644
--- a/gcc/unroll.c
+++ b/gcc/unroll.c
@@ -1410,19 +1410,6 @@ precondition_loop_p (initial_value, final_value, increment, loop_start)
       return 0;
     }
 
-  /* Now set initial_value to be the iteration_var, since that may be a
-     simpler expression, and is guaranteed to be correct if all of the
-     above tests succeed.
-
-     We can not use the initial_value as calculated, because it will be
-     one too small for loops of the form "while (i-- > 0)".  We can not
-     emit code before the loop_skip_over insns to fix this problem as this
-     will then give a number one too large for loops of the form
-     "while (--i > 0)".
-
-     Note that all loops that reach here are entered at the top, because
-     this function is not called if the loop starts with a jump.  */
-
   /* Fail if loop_iteration_var is not live before loop_start, since we need
      to test its value in the preconditioning code.  */
 
@@ -1435,7 +1422,15 @@ precondition_loop_p (initial_value, final_value, increment, loop_start)
       return 0;
     }
 
-  *initial_value = loop_iteration_var;
+  /* ??? Note that if iteration_info is modifed to allow GIV iterators
+     such as "while (i-- > 0)", the initial value will be one too small.
+     In this case, loop_iteration_var could be used to determine
+     the correct initial value, provided the loop has not been reversed.
+     
+     Also note that the absolute values of initial_value and
+     final_value are unimportant as only their difference is used for
+     calculating the number of loop iterations.  */
+  *initial_value = loop_initial_value;
   *increment = loop_increment;
   *final_value = loop_final_value;