Re: [PATCH, alpha]: Remove some_operand and some_ni_operand

[Richard Henderson <rth at redhat dot com>]

On 05/14/2015 04:40 AM, Uros Bizjak wrote:
> On Thu, May 14, 2015 at 1:31 PM, Uros Bizjak <ubizjak@gmail.com> wrote:
>> On Wed, May 13, 2015 at 8:53 PM, Richard Henderson <rth@redhat.com> wrote:
>>> On 05/13/2015 11:11 AM, Uros Bizjak wrote:
>>>> We can use general_operand instead of some_operand.
>>>>
>>>> 2015-05-13  Uros Bizjak  <ubizjak@gmail.com>
>>>>
>>>>     * config/alpha/alpha.md (extendqidi2): Use general_operand
>>>>     instead of some_operand for operand[1] predicate.
>>>>     (extendhidi2): Ditto.
>>>>     (cbranchdi4): Use general_operand instead of some_operand
>>>>     for operand[1] and operands[2] predicates.
>>>>     (cstoredi4): Ditto.
>>>>     * config/alpha/predicates.md (some_operand): Remove unused predicate.
>>>>     (some_ni_operand): Ditto.
>>>>
>>>> Tested on alpha-linux-gnu.
>>>>
>>>> Richard, does this look OK to you, or is there any other reason that
>>>> general_operand predicates were not used here?
>>>
>>> For the extensions, it was put in by Kenner in 1997 (90f6b60d), to improve code
>>> for unaligned memories.  That code was removed in 2011 by me (8b2983a3), so I
>>> think dropping some_operand there is fine.
>>>
>>> For the conditionals, it was added in 2004 by me (62350d6c), and that code is
>>> still there.  Specifically,
>>>
>>> @@ -3177,11 +3177,17 @@ alpha_emit_conditional_branch (enum rtx_code code)
>>>             cmp_code = NIL, branch_code = code;
>>>
>>>           /* If the constants doesn't fit into an immediate, but can
>>>              be generated by lda/ldah, we adjust the argument and
>>>              compare against zero, so we can use beq/bne directly.  */
>>> -         else if (GET_CODE (op1) == CONST_INT && (code == EQ || code == NE))
>>> +         /* ??? Don't do this when comparing against symbols, otherwise
>>> +            we'll reduce (&x == 0x1234) to (&x-0x1234 == 0), which will
>>> +            be declared false out of hand (at least for non-weak).  */
>>> +         else if (GET_CODE (op1) == CONST_INT
>>> +                  && (code == EQ || code == NE)
>>> +                  && !(symbolic_operand (op0, VOIDmode)
>>> +                       || (GET_CODE (op0) == REG && REG_POINTER (op0))))
>>>
>>> If I didn't use some_operand, the SYMBOL_REF would be lowered and we'll only
>>> see a REG here.  Searching the mail archive I find
>>>
>>>   https://gcc.gnu.org/ml/gcc-patches/2004-02/msg02436.html
>>>
>>> pointing to the test case gcc.dg/20040123-1.c
>>>
>>> Perhaps debugging that testcase to see what's reaching a_e_c_b in these modern
>>> times will tell you what's most appropriate.
>>
>> Both, patched and unpatched compiler generate:
>>
>> ;; Generating RTL for gimple basic block 2
>>
>> ;; if (&a == 16384B)
>>
>> (insn 5 4 6 (set (reg/f:DI 70)
>>         (symbol_ref:DI ("a") [flags 0x40]  <var_decl 0x200006f8360
>> a>)) 20040123-1.c:10 -1
>>      (nil))
>>
>> (insn 6 5 7 (set (reg:DI 71)
>>         (const_int 16384 [0x4000])) 20040123-1.c:10 -1
>>      (nil))
>>
>> (insn 7 6 8 (set (reg:DI 72)
>>         (eq:DI (reg/f:DI 70)
>>             (reg:DI 71))) 20040123-1.c:10 -1
>>      (nil))
>>
>> (jump_insn 8 7 0 (set (pc)
>>         (if_then_else (eq (reg:DI 72)
>>                 (const_int 0 [0]))
>>             (label_ref 0)
>>             (pc))) 20040123-1.c:10 -1
>>      (int_list:REG_BR_PROB 9996 (nil)))
>>
>> and gcc.dg/20040123-1.c passes for as long as I remember...
> 
> Bah, pushed send too fast.
> 
> This is what is received by a_e_c_b in both, patched and unpatched case:
> 
> Breakpoint 1, alpha_emit_conditional_branch (operands=0x7fffffffd6e0,
> cmp_mode=DImode) at
> /home/uros/gcc-svn/trunk/gcc/config/alpha/alpha.c:2508
> 2508    alpha_emit_conditional_branch (rtx operands[], machine_mode cmp_mode)
> (gdb) p debug_rtx (operands[0])
> (ne (reg/f:DI 70)
>     (const_int 16384 [0x4000]))
> $1 = void
> (gdb) p debug_rtx (operands[1])
> (reg/f:DI 70)

Ok, gotcha -- the REG_POINTER_P section of the test is still triggering.  I
suspect that the symbolic_operand test can no longer trigger.

I think the whole patch is ok.


r~