2013/11/20 Ilya Enkovich <enkovich....@gmail.com>:
> 2013/11/20 Uros Bizjak <ubiz...@gmail.com>:
>> On Wed, Nov 20, 2013 at 5:11 PM, Ilya Enkovich <enkovich....@gmail.com>
>> wrote:
>>> 2013/11/20 Uros Bizjak <ubiz...@gmail.com>:
>>>> On Wed, Nov 20, 2013 at 1:32 PM, Ilya Enkovich <enkovich....@gmail.com>
>>>> wrote:
>>>>
>>>>>> >> > Here is a patch to add size relocation and instruction to obtain
>>>>>> >> > object's size in i386 target.
>>>>>> >>
>>>>>> >> +(define_insn "move_size_reloc_<mode>"
>>>>>> >> + [(set (match_operand:SWI48 0 "register_operand" "=r")
>>>>>> >> + (match_operand:<MODE> 1 "size_relocation" "Z"))]
>>>>>> >> + ""
>>>>>> >> +{
>>>>>> >> + return "mov{<imodesuffix>}\t{%1, %0|%0, %1}";
>>>>>> >>
>>>>>> >> Please don't change x86_64_immediate_operand just to use "Z"
>>>>>> >> constraint The predicate is used in a couple of other places that for
>>>>>> >> sure don't accept your change.
>>>>>> >>
>>>>>> >> Better write this insn in an explicit way (see for example
>>>>>> >> tls_initial_exec_64_sun). Something like:
>>>>>> >>
>>>>>> >> (define_insn "move_size_reloc_<mode>"
>>>>>> >> [(set (match_operand:SWI48 0 "register_operand" "=r")
>>>>>> >> (unspec:SWI48
>>>>>> >> [(match_operand 1 "symbolic_operand" "..." )]
>>>>>> >> UNSPEC_SIZEOF))]
>>>>>> >> ""
>>>>>> >> "mov{<imodesuffix>}\t{%a1@SIZE, %0|%0, %a1@SIZE}")
>>>>>> >>
>>>>>> >> You will probably need to define new operand 1 predicate and
>>>>>> >> constraint.
>>>>>> >>
>>>>>> >> Uros.
>>>>>> >
>>>>>> > Hi, Uros! Thanks for comments! Here is what I got trying to follow
>>>>>> > your suggestion. Does it look better?
>>>>>>
>>>>>> You actually don't need any operand modifiers in the insn template.
>>>>>> Simply use:
>>>>>>
>>>>>> "mov{<imodesuffix>}\t{%1@SIZE, %0|%0, %1@SIZE}"
>>>>>>
>>>>>> and you will automatically get
>>>>>>
>>>>>> "movl $zzz, %eax" or "mov %eax, OFFSET FLAT: zzz".
>>>>>>
>>>>>> Since your pattern allows only symbolic_operand, there is no reload,
>>>>>> so you can avoid the constraint alltogether.
>>>>>>
>>>>>> BTW: Did you consider various -mcmodel=... options? For DImode moves,
>>>>>> you should check x86_64_zext_immediate_operand predicate and output
>>>>>> either "movl $zzz, %eax" or "movabs $zzz, %rax". There is no movq with
>>>>>> 64bit immediate. Please see movdi pattern.
>>>>>
>>>>> Yep, for large objects it may work wrongly. Does anyone use static
>>>>> objects >4Gb? :)
>>>>>
>>>>> Large address does not mean large object but seems we have to be
>>>>> conservative here. I added x86_64_zext_immediate_operand check with
>>>>> additional CM_KERNEL check because in this model object size should
>>>>> always fit 32 bits.
>>>>
>>>> IMO, we should list code models that support object sizes > 31bits for
>>>> 64bit target. The object size in small models will never be > 31bits
>>>> (and never negative), so we can use movl unconditionally.
>>>
>>> For medium models x86_64_zext_immediate_operand returns true for
>>> object is known to go to lower 2Gb space. It should allow us to use
>>> movl. Why do you always emit movabs for medium model?
>>
>> CM_MEDIUM has unlimited data size.
>>
>> i386-opts.h: CM_MEDIUM, /* Assumes code fits in the low 31
>> bits; data unlimited. */
>>
>> The x86_64_zext_immediate_operand allows _address_ to be loaded by
>> movl. The @SIZE reloc returns object size, which is unlimited and has
>> no connection to its address. For CM_MEDIUM,
>> x86_64_zext_immediate_operand allows:
>>
>> return (ix86_cmodel == CM_SMALL
>> || (ix86_cmodel == CM_MEDIUM
>> && !SYMBOL_REF_FAR_ADDR_P (op)));
>
> Yes, but large symbols never have SYMBOL_FLAG_FAR_ADDR set.
Sorry, I mean all large symbols have this flag set.
>
> Ilya
>
>>
>> Uros.
