(stupid_mark_refs): If setting reg set only in this insn and not

referenced, make REG_UNUSED note.

From-SVN: r14416

diff --git a/gcc/stupid.c b/gcc/stupid.c
index 396799e5da83e639bc93ea8e7a64303877f0bfc8..9a18e5555710b6f5acd760e8947996b9938859a7 100644 (file)
--- a/gcc/stupid.c
+++ b/gcc/stupid.c
@@ -1,5 +1,5 @@
 /* Dummy data flow analysis for GNU compiler in nonoptimizing mode.
-   Copyright (C) 1987, 1991, 1994, 1995, 1996, 1997 Free Software Foundation, Inc.
+   Copyright (C) 1987, 91, 94, 95, 96, 1997 Free Software Foundation, Inc.
 
 This file is part of GNU CC.
 
@@ -514,6 +514,19 @@ stupid_mark_refs (x, insn)
 
              if (last_setjmp_suid < reg_where_dead[regno])
                regs_crosses_setjmp[regno] = 1;
+
+             /* If this register is only used in this insn and is only
+                set, mark it unused.  We have to do this even when not 
+                optimizing so that MD patterns which count on this
+                behavior (e.g., it not causing an output reload on
+                an insn setting CC) will operate correctly.  */
+             if (GET_CODE (SET_DEST (x)) == REG
+                 &&& REGNO_FIRST_UID (regno) == INSN_UID (insn)
+                 && REGNO_LAST_UID (regno) == INSN_UID (insn)
+                 && (code == CLOBBER || ! reg_mentioned_p (SET_DEST (x),
+                                                           SET_SRC (x))))
+               REG_NOTES (insn) = gen_rtx (EXPR_LIST, REG_UNUSED,
+                                           SET_DEST (x), REG_NOTES (insn));
            }
        }