Re: [PATCH] Tame path_range_query::compute_imports

[Andrew MacLeod <amacleod@redhat.com>]

On 8/16/22 05:28, Richard Biener wrote:
> On Tue, 16 Aug 2022, Aldy Hernandez wrote:
>
>> On Tue, Aug 16, 2022 at 11:08 AM Aldy Hernandez <aldyh@redhat.com> wrote:
>>> On Tue, Aug 16, 2022 at 10:32 AM Richard Biener <rguenther@suse.de> wrote:
>>>> On Tue, 16 Aug 2022, Aldy Hernandez wrote:
>>>>
>>>>> On Thu, Aug 11, 2022 at 1:42 PM Richard Biener <rguenther@suse.de> wrote:
>>>>>
>>>>>> @@ -599,6 +592,30 @@ path_range_query::compute_imports (bitmap imports, const vec<basic_block> &path)
>>>>>>                  worklist.safe_push (arg);
>>>>>>              }
>>>>>>          }
>>>>>> +      else if (gassign *ass = dyn_cast <gassign *> (def_stmt))
>>>>>> +       {
>>>>>> +         tree ssa[3];
>>>>>> +         if (range_op_handler (ass))
>>>>>> +           {
>>>>>> +             ssa[0] = gimple_range_ssa_p (gimple_range_operand1 (ass));
>>>>>> +             ssa[1] = gimple_range_ssa_p (gimple_range_operand2 (ass));
>>>>>> +             ssa[2] = NULL_TREE;
>>>>>> +           }
>>>>>> +         else if (gimple_assign_rhs_code (ass) == COND_EXPR)
>>>>>> +           {
>>>>>> +             ssa[0] = gimple_range_ssa_p (gimple_assign_rhs1 (ass));
>>>>>> +             ssa[1] = gimple_range_ssa_p (gimple_assign_rhs2 (ass));
>>>>>> +             ssa[2] = gimple_range_ssa_p (gimple_assign_rhs3 (ass));
>>>>>> +           }
>>>>>> +         else
>>>>>> +           continue;
>>>>>> +         for (unsigned j = 0; j < 3; ++j)
>>>>>> +           {
>>>>>> +             tree rhs = ssa[j];
>>>>>> +             if (rhs && add_to_imports (rhs, imports))
>>>>>> +               worklist.safe_push (rhs);
>>>>>> +           }
>>>>>> +       }
>>>>> We seem to have 3 copies of this copy now: this one, the
>>>>> threadbackward one, and the original one.
>>>>>
>>>>> Could we abstract this somehow?
>>>> I've thought about this but didn't find any good solution since the
>>>> use of the operands is always a bit different.  But I was wondering
>>>> why/if the COND_EXPR special-casing is necessary, that is, why
>>>> don't we have a range_op_handler for it and if we don't why
>>>> do we care about it?

Simply that range-ops is defined as always being one or 2 use operands. 
everything is streamlined for those common cases.  There is no support 
in the API for a 3rd field. All non-conforming stmts are "unique" and 
thus require some level of specialization.  I am not aware of any other 
3 operand stmt we would care about, so at the time it seemed easier to 
leave cond-expr as a specialization, in theory localized.

as for the abstraction, its easy enough to provide a routine which will 
take a vector and fill it with ssa_names we might care about on the 
stmt.. then each caller can do their own little specialized bit.  I 
never expected for that sequence to become common place :-)

>>> I think it's because we don't have a range-op handler for COND_EXPR,
>>> opting to handle the relational operators instead in range-ops.  We
>>> have similar code in the folder:
>>>
>>>    if (range_op_handler (s))
>>>      res = range_of_range_op (r, s, src);
>>>    else if (is_a<gphi *>(s))
>>>      res = range_of_phi (r, as_a<gphi *> (s), src);
>>>    else if (is_a<gcall *>(s))
>>>      res = range_of_call (r, as_a<gcall *> (s), src);
>>>    else if (is_a<gassign *> (s) && gimple_assign_rhs_code (s) == COND_EXPR)
>>>      res = range_of_cond_expr (r, as_a<gassign *> (s), src);
>>>
>>> Andrew, do you have any suggestions here?
>> Hmmm, so thinking about this, perhaps special casing it is the way to go ??
> It looks like so.  Though a range_op_handler could, for
> _1 = _2 ? _3 : _4; derive a range for _3 from _1 if _2 is
> known true?
>
the fold_using_range class does this for the forward direction, and my 
intention (just havent gotten to it yet), was to add similar 
specialization in GORI rather than expanding range-ops just for the one 
stmt... in much the same way that range_of_cond_expr works.

It should be localized to gori_compute::compute_operand_range () , where:

  range_op_handler handler(stmt);
   if (!handler)
     return false;

before returning, we check if its a COND_EXPR, and if so, call a 
specialized compute routine to look at the various operands and invoke 
any continued operand ranges as approriate.    It should be quite trivial..

   I'll take a look at adding COND_EXPR to GORI, and privoide that 
routine somewhere.. probably as a function as part of 
gimple-range-fold.h so it can potentially apply to any stmt.

Andrew