ifcvt.c (noce_process_if_block): Re-add check vs X being changed in no-else-block case.

        * ifcvt.c (noce_process_if_block): Re-add check vs X being changed
        in no-else-block case.  Add commentary.

From-SVN: r61695

gcc/ChangeLog

+2003-01-23  Richard Henderson  <rth@redhat.com>
+
+        * ifcvt.c (noce_process_if_block): Re-add check vs X being changed
+        in no-else-block case.  Add commentary.
+
 2003-01-23  Kaveh R. Ghazi  <ghazi@caip.rutgers.edu>
 
 	* configure.in: Revert last change.

gcc/ifcvt.c

@@ -1802,15 +1802,22 @@ noce_process_if_block (ce_info)
   else
     {
       insn_b = prev_nonnote_insn (if_info.cond_earliest);
+      /* We're going to be moving the evaluation of B down from above
+	 COND_EARLIEST to JUMP.  Make sure the relevant data is still
+	 intact.  */
       if (! insn_b
 	  || GET_CODE (insn_b) != INSN
 	  || (set_b = single_set (insn_b)) == NULL_RTX
 	  || ! rtx_equal_p (x, SET_DEST (set_b))
-	  || reg_overlap_mentioned_p (x, cond)
-	  || reg_overlap_mentioned_p (x, a)
 	  || reg_overlap_mentioned_p (x, SET_SRC (set_b))
 	  || modified_between_p (SET_SRC (set_b),
-				 PREV_INSN (if_info.cond_earliest), jump))
+				 PREV_INSN (if_info.cond_earliest), jump)
+	  /* Likewise with X.  In particular this can happen when
+	     noce_get_condition looks farther back in the instruction
+	     stream than one might expect.  */
+	  || reg_overlap_mentioned_p (x, cond)
+	  || reg_overlap_mentioned_p (x, a)
+	  || modified_between_p (x, PREV_INSN (if_info.cond_earliest), jump))
 	insn_b = set_b = NULL_RTX;
     }
   b = (set_b ? SET_SRC (set_b) : x);