Re: [PATCH GCC8][07/33]Offset validity check in address expression

[Richard Biener <richard dot guenther at gmail dot com>]

On Thu, May 4, 2017 at 5:17 PM, Bin.Cheng <amker.cheng@gmail.com> wrote:
> On Wed, May 3, 2017 at 10:49 AM, Richard Biener
> <richard.guenther@gmail.com> wrote:
>> On Tue, May 2, 2017 at 7:06 PM, Bin.Cheng <amker.cheng@gmail.com> wrote:
>>> On Mon, Apr 24, 2017 at 11:34 AM, Richard Biener
>>> <richard.guenther@gmail.com> wrote:
>>>> On Tue, Apr 18, 2017 at 12:41 PM, Bin Cheng <Bin.Cheng@arm.com> wrote:
>>>>> Hi,
>>>>> For now, we check validity of offset by computing the maximum offset then checking if
>>>>> offset is smaller than the max offset.  This is inaccurate, for example, some targets
>>>>> may require offset to be aligned by power of 2.  This patch introduces new interface
>>>>> checking validity of offset.  It also buffers rtx among different calls.
>>>>>
>>>>> Is it OK?
>>>>
>>>> -  static vec<HOST_WIDE_INT> max_offset_list;
>>>> -
>>>> +  auto_vec<rtx> addr_list;
>>>>    as = TYPE_ADDR_SPACE (TREE_TYPE (use->iv->base));
>>>>    mem_mode = TYPE_MODE (TREE_TYPE (*use->op_p));
>>>>
>>>> -  num = max_offset_list.length ();
>>>> +  num = addr_list.length ();
>>>>    list_index = (unsigned) as * MAX_MACHINE_MODE + (unsigned) mem_mode;
>>>>    if (list_index >= num)
>>>>
>>>> num here is always zero and thus the compare is always true.
>>>>
>>>> +      addr_list.safe_grow_cleared (list_index + MAX_MACHINE_MODE);
>>>> +      for (; num < addr_list.length (); num++)
>>>> +       addr_list[num] = NULL;
>>>>
>>>> the loop is now redundant (safe_grow_cleared)
>>>>
>>>> +  addr = addr_list[list_index];
>>>> +  if (!addr)
>>>>      {
>>>>
>>>> always true again...
>>>>
>>>> I wonder if you really indented to drop 'static' from addr_list?
>>>> There's no caching
>>>> across function calls.
>>> Right, the redundancy is because I tried to cache across function
>>> calls with declarations like:
>>>   static unsigned num = 0;
>>>   static GTY ((skip)) rtx *addr_list = NULL;
>>> But this doesn't work, the addr_list[list_index] still gets corrupted somehow.
>>
>> Well, you need GTY (()), not GTY((skip)) on them.  Not sure if it works
>> for function-scope decls, you have to check.  Look at whether a GC
>> root is created for the variable in gt-tree-ssa-loop-ivopts.h (need to tweak
>> GTFILES in the makefile plus include that generated file).  tree-ssa-address.c
>> uses a global root for mem_addr_template_list for example.
> Thanks for helping, patch updated.
> Bootstrap and test on x86_64.  Is it OK?

Yes.

Thanks,
Richard.

> Thanks,
> bin
>
> 2017-05-02  Bin Cheng  <bin.cheng@arm.com>
>
>     * Makefile.in (GTFILES): Add tree-ssa-loop-ivopts.c.
>     * tree-ssa-loop-ivopts.c (compute_max_addr_offset): Delete.
>     (addr_list, addr_offset_valid_p): New.
>     (split_address_groups): Check offset validity with above function.
>     (gt-tree-ssa-loop-ivopts.h): Include.
>
>>>>
>>>>
>>>>
>>>>> Thanks,
>>>>> bin
>>>>> 2017-04-11  Bin Cheng  <bin.cheng@arm.com>
>>>>>
>>>>>         * tree-ssa-loop-ivopts.c (compute_max_addr_offset): Delete.
>>>>>         (addr_offset_valid_p): New function.
>>>>>         (split_address_groups): Check offset validity with above function.