decrement and branch optimization broken?

[Roman Zippel <zippel at linux-m68k dot org>]

Hi,

I can't get 3.x to produce dbra instructions on m68k anymore.
For e.g.:

int f(void);

void f1(void)
{
        short i = 32;
        do {
                f();
        } while (--i >= 0);
}

2.95 produces this:

        lea f,%a2
.L6:
        jbsr (%a2)
        dbra %d2,.L6

The problem is that the combine pass doesn't optimize this:

(insn 21 18 23 (set (reg/v:HI 29)
        (plus:HI (reg/v:HI 29)
            (const_int -1 [0xffffffff]))) 101 {addhi3} (nil)
    (nil))

(insn 23 21 24 (set (cc0)
        (reg/v:HI 29)) 4 {*m68k.md:384} (insn_list 21 (nil))
    (nil))

(jump_insn 24 23 28 (set (pc)
        (if_then_else (ge (cc0)
                (const_int 0 [0x0]))
            (label_ref 11)
            (pc))) 322 {bge} (nil)
    (expr_list:REG_BR_PROB (const_int 9697 [0x25e1])
        (expr_list:REG_NONNEG (reg/v:HI 29)
            (nil))))

into this anymore:

(jump_insn 32 31 36 (parallel[ 
            (set (pc)
                (if_then_else (ge (plus:HI (reg/v:HI 29)
                            (const_int -1 [0xffffffff]))
                        (const_int 0 [0x0]))
                    (label_ref 35)
                    (pc)))
            (set (reg/v:HI 29)
                (plus:HI (reg/v:HI 29)
                    (const_int -1 [0xffffffff])))
        ] ) 409 {decrement_and_branch_until_zero-1} (nil)
    (expr_list:REG_NONNEG (nil)
        (expr_list:REG_NONNEG (nil)
            (nil))))

Does anyone has an idea, what goes wrong or how to fix this?

bye, Roman