llvm dev - Mar 2015 - [LLVMdev] LLD: representation of a power of two value

On Tue, Mar 24, 2015 at 5:40 PM, Nick Kledzik <kledzik at apple.com>
wrote:
>
> On Mar 24, 2015, at 5:09 PM, Rui Ueyama <ruiu at google.com> wrote:
>
> > It's not a big deal, but it always annoyed me a bit when I hit it,
so
> I'll bring it up here.
> >
> > LLD represents an alignment X as log2(X) in some places and just X in
> other places. It's a bit confusing. Because I always think alignments
in my
> mind in terms of 1, 2, 4, 8, ..., instead of 2^1, 2^2, 2^3, ..., I'd
like
> to propose to always use real values.
> Can you give some examples?
>
> The DefinedAtom class has struct:
>
>     struct Alignment {
>         uint16_t powerOf2;
>         uint16_t modulus;
>     };
>
> That use seems clear.   But, yes, if there is “int alignment” somewhere,
> that is ambiguous.
>
At least in ELF, alignment values are represented not by exponents but by
just numbers in files, so we convert them back and force. "Alignment"
is
used for both exponents and actual values there.
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On 3/24/2015 7:51 PM, Rui Ueyama wrote:
> On Tue, Mar 24, 2015 at 5:40 PM, Nick Kledzik <kledzik at apple.com>
wrote:
>
>> On Mar 24, 2015, at 5:09 PM, Rui Ueyama <ruiu at google.com>
wrote:
>>
>>> It's not a big deal, but it always annoyed me a bit when I hit
it, so
>> I'll bring it up here.
>>> LLD represents an alignment X as log2(X) in some places and just X
in
>> other places. It's a bit confusing. Because I always think
alignments in my
>> mind in terms of 1, 2, 4, 8, ..., instead of 2^1, 2^2, 2^3, ...,
I'd like
>> to propose to always use real values.
>> Can you give some examples?
>>
>> The DefinedAtom class has struct:
>>
>>      struct Alignment {
>>          uint16_t powerOf2;
>>          uint16_t modulus;
>>      };
>>
>> That use seems clear.   But, yes, if there is “int alignment”
somewhere,
>> that is ambiguous.
>>
> At least in ELF, alignment values are represented not by exponents but by
> just numbers in files, so we convert them back and force.
"Alignment" is
> used for both exponents and actual values there.
I believe you are mentioning about section alignments, that are being 
differentiated from atom alignments ?

If so are you planning to change the variable name (or) use Alignment 
even there ?

Shankar Easwaran

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by the
Linux Foundation

I guess I'm talking about atoms. Do we have notion of section in LLD?

On Wed, Mar 25, 2015 at 8:35 AM, Shankar Easwaran <shankare at
codeaurora.org>
wrote:
> On 3/24/2015 7:51 PM, Rui Ueyama wrote:
>
>> On Tue, Mar 24, 2015 at 5:40 PM, Nick Kledzik <kledzik at
apple.com> wrote:
>>
>>  On Mar 24, 2015, at 5:09 PM, Rui Ueyama <ruiu at google.com>
wrote:
>>>
>>>  It's not a big deal, but it always annoyed me a bit when I hit
it, so
>>>>
>>> I'll bring it up here.
>>>
>>>> LLD represents an alignment X as log2(X) in some places and
just X in
>>>>
>>> other places. It's a bit confusing. Because I always think
alignments in
>>> my
>>> mind in terms of 1, 2, 4, 8, ..., instead of 2^1, 2^2, 2^3, ...,
I'd like
>>> to propose to always use real values.
>>> Can you give some examples?
>>>
>>> The DefinedAtom class has struct:
>>>
>>>      struct Alignment {
>>>          uint16_t powerOf2;
>>>          uint16_t modulus;
>>>      };
>>>
>>> That use seems clear.   But, yes, if there is “int alignment”
somewhere,
>>> that is ambiguous.
>>>
>>>  At least in ELF, alignment values are represented not by exponents
but
>> by
>> just numbers in files, so we convert them back and force.
"Alignment" is
>> used for both exponents and actual values there.
>>
> I believe you are mentioning about section alignments, that are being
> differentiated from atom alignments ?
>
> If so are you planning to change the variable name (or) use Alignment even
> there ?
>
> Shankar Easwaran
>
> --
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted
> by the Linux Foundation
>
>
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