(fill_slots_from_thread): When replacing a use of a register with what it was set...

(fill_slots_from_thread): When replacing a use of a register with what
it was set to, don't do it when either the destination or source of
the copy is set in the insn.

From-SVN: r4716

diff --git a/gcc/reorg.c b/gcc/reorg.c
index 3b6b20585d3fdcb8ee353f978dbcf01c718eaf9d..5b89943a24b0064156fcff697d27f614e0e87580 100644 (file)
--- a/gcc/reorg.c
+++ b/gcc/reorg.c
@@ -3237,9 +3237,11 @@ fill_slots_from_thread (insn, condition, thread, opposite_thread, likely,
         but it doesn't seem worth it.  It might also be a good idea to try
         to swap the two insns.  That might do better.
 
-        We can't do this if the next insn modifies our source, because that
-        would make the replacement into the insn invalid.  This also
-        prevents updating the contents of a PRE_INC.  */
+        We can't do this if the next insn modifies our destination, because
+        that would make the replacement into the insn invalid.  We also can't
+        do this if it modifies our source, because it might be an earlyclobber
+        operand.  This latter test also prevents updating the contents of
+        a PRE_INC.  */
 
       if (GET_CODE (trial) == INSN && GET_CODE (pat) == SET
          && GET_CODE (SET_SRC (pat)) == REG
@@ -3250,6 +3252,7 @@ fill_slots_from_thread (insn, condition, thread, opposite_thread, likely,
          if (next && GET_CODE (next) == INSN
              && GET_CODE (PATTERN (next)) != USE
              && ! reg_set_p (SET_DEST (pat), next)
+             && ! reg_set_p (SET_SRC (pat), next)
              && reg_referenced_p (SET_DEST (pat), PATTERN (next)))
            validate_replace_rtx (SET_DEST (pat), SET_SRC (pat), next);
        }