[LLVMdev] builtin_apply?

[Jan Smets]

I would also like so tee support for __builtin_apply*. We use it in 
macros and such.
If others are interested, please speak up.
-Jan

On 02/10/2013 20:51, Patrik Hägglund H wrote:
> Indeed. However, I wouldn't have called variable number of arguments a "sophisticated feature".  :-)
>
> /Patrik Hägglund
>
> -----Original Message-----
> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On Behalf Of Krzysztof Parzyszek
> Sent: den 2 oktober 2013 19:12
> To: llvmdev at cs.uiuc.edu
> Subject: Re: [LLVMdev] builtin_apply?
>
> I think varargs functions would be an example of where this builtin
> would not work.
>
> -K
>
>
> On 10/2/2013 2:32 AM, Patrik Hägglund H wrote:
>> Interesting. Just having __builtin_apply_args() (and a correspoding
>> __builtin_apply_args_size()), would make it possible to do a memcpy
>> store of arguments to a (varargs) function, which sometimes is useful
>> for our users (for debug/trace purposes).
>>
>> /Patrik Hägglund
>>
>> *From:*llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu]
>> *On Behalf Of *Eric Christopher
>> *Sent:* den 2 oktober 2013 07:22
>> *To:* reed kotler
>> *Cc:* LLVMdev at cs.uiuc.edu
>> *Subject:* Re: [LLVMdev] builtin_apply?
>>
>> __builtin_apply is an abomination. Even in GCC it is held to have been a
>> bad idea.
>>
>> --eric
>>
>> On Oct 1, 2013 10:03 PM, "reed kotler" <rkotler at mips.com
>> <mailto:rkotler at mips.com>> wrote:
>>
>> why does clang not support builtin_apply?
>>
>>
>>        6.5 Constructing Function Calls
>>
>> Using the built-in functions described below, you can record the
>> arguments a function received, and call another function with the same
>> arguments, without knowing the number or types of the arguments.
>>
>> You can also record the return value of that function call, and later
>> return that value, without knowing what data type the function tried to
>> return (as long as your caller expects that data type).
>>
>> However, these built-in functions may interact badly with some
>> sophisticated features or other extensions of the language. It is,
>> therefore, not recommended to use them outside very simple functions
>> acting as mere forwarders for their arguments.
>>
>> - Built-in Function: void * *__builtin_apply_args* ()
>>
>> This built-in function returns a pointer to data describing how to
>> perform a call with the same arguments as are passed to the current
>> function.
>>
>> The function saves the arg pointer register, structure value address,
>> and all registers that might be used to pass arguments to a function
>> into a block of memory allocated on the stack. Then it returns the
>> address of that block.
>>
>> - Built-in Function: void * *__builtin_apply* (void (*function)(), void
>> *arguments, size_t size)
>>
>> This built-in function invokes function with a copy of the parameters
>> described by arguments and size.
>>
>> The value of arguments should be the value returned by
>> |__builtin_apply_args|. The argument size specifies the size of the
>> stack argument data, in bytes.
>>
>> This function returns a pointer to data describing how to return
>> whatever value is returned by function. The data is saved in a block of
>> memory allocated on the stack.
>>
>> It is not always simple to compute the proper value for size. The value
>> is used by |__builtin_apply| to compute the amount of data that should
>> be pushed on the stack and copied from the incoming argument area.
>>
>>
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>>
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>