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Re: Question on operand_equal_p on different type conversion expressions


On Tue, May 21, 2013 at 8:38 AM, Bin.Cheng <amker.cheng@gmail.com> wrote:
> On Tue, May 21, 2013 at 1:55 PM, Andrew Pinski <pinskia@gmail.com> wrote:
>> On Mon, May 20, 2013 at 10:50 PM, Bin.Cheng <amker.cheng@gmail.com> wrote:
>
>>
>>
>> NOP_EXPR here is a misnamed tree really.  It could also be a
>> CONVERT_EXPR and still have the same issue as the types are not the
>> same.
>>
>>
>>> The problem is operand_equal_q simply return false because arg0/arg1
>>> have different tree code.
>>
>> No it returns false because the types are two different.  One is
>> signed and the other is unsigned.
>>
>>>
>>> Should operand_equal_q take two kinds of conversion expression into
>>> consideration, or arg0/arg1 are not equal? Thanks.
>>
>> Yes why would it not?  Look at the resulting types again.
>
> Thanks very much. The dumped tree codes are different (my mistake).
> But the problem still exists in operand_equal_q.
> For now with below tree nodes,
> arg0:
> <convert_expr 0xb72ddb04
>     type <integer_type 0xb74602a0 short int sizes-gimplified public HI
>         size <integer_cst 0xb744e7c4 constant 16>
>         unit size <integer_cst 0xb744e7e0 constant 2>
>         align 16 symtab 0 alias set 4 canonical type 0xb74602a0
> precision 16 min <integer_cst 0xb744e770 -32768> max <integer_cst
> 0xb744e78c 32767> context <translation_unit_decl 0xb760dd80 D.6120>
>         pointer_to_this <pointer_type 0xb7241600>>
>
>     arg 0 <ssa_name 0xb72882f8
>         type <integer_type 0xb7460420 long int sizes-gimplified public SI
>             size <integer_cst 0xb744e55c constant 32>
>             unit size <integer_cst 0xb744e578 constant 4>
>             align 32 symtab 0 alias set 5 canonical type 0xb7460420
> precision 32 min <integer_cst 0xb744e888 -2147483648> max <integer_cst
> 0xb744e8a4 2147483647> context <translation_unit_decl 0xb760dd80
> D.6120>
>             pointer_to_this <pointer_type 0xb74677e0>>
>         visiteddef_stmt _23 = *_22;
>
>         version 23>>
>
> arg1:
> <nop_expr 0xb72e1b54
>     type <integer_type 0xb74602a0 short int sizes-gimplified public HI
>         size <integer_cst 0xb744e7c4 constant 16>
>         unit size <integer_cst 0xb744e7e0 constant 2>
>         align 16 symtab 0 alias set 4 canonical type 0xb74602a0
> precision 16 min <integer_cst 0xb744e770 -32768> max <integer_cst
> 0xb744e78c 32767> context <translation_unit_decl 0xb760dd80 D.6120>
>         pointer_to_this <pointer_type 0xb7241600>>
>
>     arg 0 <ssa_name 0xb72882f8
>         type <integer_type 0xb7460420 long int sizes-gimplified public SI
>             size <integer_cst 0xb744e55c constant 32>
>             unit size <integer_cst 0xb744e578 constant 4>
>             align 32 symtab 0 alias set 5 canonical type 0xb7460420
> precision 32 min <integer_cst 0xb744e888 -2147483648> max <integer_cst
> 0xb744e8a4 2147483647> context <translation_unit_decl 0xb760dd80
> D.6120>
>             pointer_to_this <pointer_type 0xb74677e0>>
>         visiteddef_stmt _23 = *_22;
>
>         version 23>>
>
> The operand_equal_p still returns false because below piece of code in it:
>
> #if 1
>   if (TREE_CODE (arg0) != TREE_CODE (arg1)
>       /* This is needed for conversions and for COMPONENT_REF.
>      Might as well play it safe and always test this.  */
>       || TREE_CODE (TREE_TYPE (arg0)) == ERROR_MARK
>       || TREE_CODE (TREE_TYPE (arg1)) == ERROR_MARK
>       || TYPE_MODE (TREE_TYPE (arg0)) != TYPE_MODE (TREE_TYPE (arg1)))
> #else
>   if ((TREE_CODE (arg0) != TREE_CODE (arg1)
>        && !(CONVERT_EXPR_P (arg0) && CONVERT_EXPR_P (arg1)))
>       /* This is needed for conversions and for COMPONENT_REF.
>      Might as well play it safe and always test this.  */
>       || TREE_CODE (TREE_TYPE (arg0)) == ERROR_MARK
>       || TREE_CODE (TREE_TYPE (arg1)) == ERROR_MARK
>       || TYPE_MODE (TREE_TYPE (arg0)) != TYPE_MODE (TREE_TYPE (arg1)))
> #endif
>     return 0;
>
>
> The code in else part should be used instead, right?

As this code is used by frontends who may actually have different behaviors
for NOP_EXPR vs. CONVERT_EXPR (which is the only reason the two
tree codes still exist!) it isn't 100% obvious.  Though if it passes testing
then it's ok IMHO, but I'd like you to refactor the above to

    if (TREE_CODE (arg0) != TREE_CODE (arg1)
        /* NOP_EXPR and CONVERT_EXPR are considered equal.  */
        && !(CONVERT_EXPR_P (arg0) && CONVERT_EXPR_P (arg1)))
      return 0;

    /* This is needed for conversions and for COMPONENT_REF.
         Might as well play it safe and always test this.  */
    if (TREE_CODE (TREE_TYPE (arg0)) == ERROR_MARK
      || TREE_CODE (TREE_TYPE (arg1)) == ERROR_MARK
      || TYPE_MODE (TREE_TYPE (arg0)) != TYPE_MODE (TREE_TYPE (arg1)))
      return 0;

ok if that passes testing.

Thanks,
Richard.

> Thanks.
>
> --
> Best Regards.


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