[Mono-dev] SIZEOF_VOID_P in the JIT

[Zoltan Varga]

Hi,

  The approach looks fine.

            Zoltan

On Thu, Dec 11, 2008 at 4:56 AM, Mark Mason <mmason at upwardaccess.com> wrote:
> Hello,
>
>
> On Thu, 2008-12-11 at 01:40 -0200, Rodrigo Kumpera wrote:
>> Hi Mark,
>>
>> Do you have an idea of how big such change would be?
>
> There's ~154 uses of SIZEOF_VOID_P under mono/.
>
> What I'm proposing would actually leave them all alone to begin with -
> and I'm fairly certain that most all of them would never need to be
> touched.  I'd just introduce a new define, and propagate it through the
> code base on a case-by-case basis as I find pieces that do need to be
> updated.
>
> For everyone except mips/n32, SIZEOF_VOID_P == SIZEOF_REGISTER, so even
> when I do the substitution, there will be no change in behavior.
>
> But - before I go introducing such changes, I'd like to get a blessing
> on the concept, and on the name of the new macro.
>
> This just seems a lot cleaner to me than putting:
>
> #if defined(__mips__) && (_MIPS_SIM == _ABIN32)
>
> tests in the non-mips specific files instead.
>
>
> Thanks,
> Mark
>
>>
>> Cheers,
>> Rodrigo
>>
>> On Thu, Dec 11, 2008 at 1:21 AM, Mark Mason <mmason at upwardaccess.com>
>> wrote:
>>         Hello all,
>>
>>         The current JIT code assumes that SIZEOF_VOID_P is also the
>>         size of
>>         registers (as per the calling convention that we're generating
>>         code
>>         for). There's a fair number of #if tests for this in the
>>         mono/mini
>>         directory (as well as in a few others).
>>
>>         What brings this up is porting to mips/n32, a calling
>>         convention which
>>         uses the 'usual' 32-bit types for C language constructs:
>>
>>                sizeof(int) = 4
>>                sizeof(void *) = 4
>>                sizeof(long) = 4
>>                sizeof(float) = 8
>>                sizeof(double) = 8
>>                sizeof(long long) = 8
>>
>>         But where registers are 64-bits instead of 32-bits, and we
>>         need to
>>         generate any number of 64-bit operations under the hood for
>>         loads/stores
>>         into stack slots, parameter passing, return values, etc.
>>
>>         Since SIZEOF_VOID_P is still 4 on this target,
>>         mono_decompose_long_opts() insists on breaking up long
>>         operands that I'd
>>         rather stayed together. Rather than putting in a lot of MIPS
>>         specific
>>         #ifdef tests in the generic code, I'd like to suggest
>>         splitting the
>>         current usage of SIZEOF_VOID_P -- using SIZEOF_VOID_P to
>>         represent the
>>         size of addresses, and a new define (SIZEOF_REGISTER maybe?)
>>         to
>>         represent the size of general purpose machine registers. On
>>         most all
>>         targets, SIZEOF_VOID_P == SIZEOF_REGISTER and everything will
>>         behave as
>>         it does today. For mips/n32, SIZEOF_VOID_P=4,
>>         SIZEOF_REGISTER=8 and
>>         we'll get the desired behavior we want there.
>>
>>         Thoughts? Does someone see a better way to handle this?
>>
>>         Thanks in advance.
>>         Mark
>>
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>>
>
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