llvm dev - Sep 2012 - [LLVMdev] Detail question about how to implement Win64 SEH

Hi!

I try to add more functionality to Win64 exception handling, based on 
the posted patches from Charles Davis and João Matos.

But I have a question about how to map SEH handling to LLVM IR.

The basic structure of SEH in C is as follows:

   __try {
     // Do something.
   }
   __except (filter(GetExceptionCode(), GetExceptionInformation()))
   {
     // Handle exception
   }

How to translate this?

- The filter expression is basically a nested function which is called 
with the exception code and exception information.
- The body of the __except statement is the landing pad. It is always 
executed if the filter expression returns 1.
- The exception machinery first asks _C_specific_handler, which calls 
the filter expression and possible jump to the body of the __except 
statement.

Everything looks fine except that I need a reference to the filter 
expression in order to generate the EH tables.
Is there a way to associate the filter expression with the landingpad 
instruction? I am qite sure that I miss here some LLVM API or idiom....

Regards

Kai

Hi Kai,
> I try to add more functionality to Win64 exception handling, based on the
posted
> patches from Charles Davis and João Matos.
>
> But I have a question about how to map SEH handling to LLVM IR.
are you sure you don't mean: map LLVM IR to SEH?  I.e. are you talking about
how to implement LLVM's "dwarf" exception handling intrinsics and
landingpad
instruction using SEH?

Ciao, Duncan.
>
> The basic structure of SEH in C is as follows:
>
>    __try {
>      // Do something.
>    }
>    __except (filter(GetExceptionCode(), GetExceptionInformation()))
>    {
>      // Handle exception
>    }
>
> How to translate this?
>
> - The filter expression is basically a nested function which is called with
the
> exception code and exception information.
> - The body of the __except statement is the landing pad. It is always
executed
> if the filter expression returns 1.
> - The exception machinery first asks _C_specific_handler, which calls the
filter
> expression and possible jump to the body of the __except statement.
>
> Everything looks fine except that I need a reference to the filter
expression in
> order to generate the EH tables.
> Is there a way to associate the filter expression with the landingpad
> instruction? I am qite sure that I miss here some LLVM API or idiom....
>
> Regards
>
> Kai
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

Hi Duncan!

On 17.09.2012 19:51, Duncan Sands wrote:
> Hi Kai,
>
>> I try to add more functionality to Win64 exception handling, based on
>> the posted
>> patches from Charles Davis and João Matos.
>>
>> But I have a question about how to map SEH handling to LLVM IR.
>
> are you sure you don't mean: map LLVM IR to SEH?  I.e. are you talking
> about
> how to implement LLVM's "dwarf" exception handling intrinsics
and
> landingpad
> instruction using SEH?
Maybe my sentence was not precise enough. Yes, I want to implement 
LLVM's "dwarf" exception handling by using SEH. And I want to do
it in a
way that it is possible to map the C code below to LLVM IR.

Regards
Kai
>
> Ciao, Duncan.
>
>>
>> The basic structure of SEH in C is as follows:
>>
>>    __try {
>>      // Do something.
>>    }
>>    __except (filter(GetExceptionCode(), GetExceptionInformation()))
>>    {
>>      // Handle exception
>>    }
>>
>> How to translate this?
>>
>> - The filter expression is basically a nested function which is called
>> with the
>> exception code and exception information.
>> - The body of the __except statement is the landing pad. It is always
>> executed
>> if the filter expression returns 1.
>> - The exception machinery first asks _C_specific_handler, which calls
>> the filter
>> expression and possible jump to the body of the __except statement.
>>
>> Everything looks fine except that I need a reference to the filter
>> expression in
>> order to generate the EH tables.
>> Is there a way to associate the filter expression with the landingpad
>> instruction? I am qite sure that I miss here some LLVM API or idiom....
>>
>> Regards
>>
>> Kai
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev