6 GCC regressions, 2 new, with your patch on 2002-07-20T23:26:42Z.

[Richard Henderson]

On Sun, Jul 21, 2002 at 09:38:43PM +0200, Jan Hubicka wrote:
> This is really interesting case.  The beggining of function contains:
> (insn 4 3 6 0 (nil) (set (reg:SI 62)
>         (mem/f:SI (plus:SI (reg/f:SI 16 argp)
>                 (const_int 4 [0x4])) [4 y+0 S4 A32])) 45 {*movsi_1}
> (nil)
>     (expr_list:REG_EQUIV (mem/f:SI (plus:SI (reg/f:SI 16 argp)
>                 (const_int 4 [0x4])) [4 y+0 S4 A32])
>         (nil)))
> 
> And later also:
> 
> (insn 12 6 21 0 0x401a3a80 (set (reg/v/f:SI 64)
>         (mem/f:SI (plus:SI (reg/f:SI 16 argp)
>                 (const_int 4 [0x4])) [4 S4 A8])) 45 {*movsi_1} (nil)
>     (nil))
> 
> cselib notices the equivalence and cprop actually does the replacement
> of reg 64 by reg 62.  But the REG_EQUIV note is not really valid, as the
> value of memory copy y is not valid during the function (overwriten by
> bar call).

Your reasoning is incorrect.  REG_EQUIV is a _local_ equivalence,
free to be killed at any moment.  REG_EQUAL is the global equivalence.

Irritatingly, the test case isn't failing for me at the moment, so
I can't make any more progress here.


r~