llvm dev - May 2013 - [LLVMdev] [llvm-c]

Hello,

a few days ago, I was trying to access the LLVM target registry via the
LLVM-C interface. Unfortunately I can't seem to get some useful
information out of it.

Despite the fact that the following code is written in Pascal, can you
please tell me if I have done something wrong here?

// initialize all targets / target information
LLVMInitializeAllTargets;
LLVMInitializeAllTargetInfos;

// initialize native target in particular
LLVMInitializeNativeTarget;

// get first target
Target := LLVMGetFirstTarget;

// loop until the target is NULL
while (Target <> nil) do
begin
  // get target name & description
  TargetName := LLVMGetTargetName(Target);
  TargetDescription := LLVMGetTargetDescription(Target);

  // do something with these information

  Target := LLVMGetNextTarget(Target);
end;

By debugging the LLVM library (a custom DLL, which works fine
otherwise), I can see that there is no information, but I'm not that
deep into C and the LLVM structure to identify what went wrong. Also I
did a lot of tests the other day, trying several things without luck.

However, since I do not need this code at the moment, it's not urgent,
just felt to let you know about my problems.

Kind regards,

    Christian

-- 
Christian-W. Budde
Eleonorenstr. 17
30449 Hannover
Tel.: +49 511 31048857
E-Mail: Christian at savioursofsoul.de
WWW: http://www.savioursofsoul.de/Christian

On Sat, May 11, 2013 at 01:48:44PM +0200, Christian Budde
wrote:
> Hello,
> 
> a few days ago, I was trying to access the LLVM target registry via the
> LLVM-C interface. Unfortunately I can't seem to get some useful
> information out of it.
> 
> Despite the fact that the following code is written in Pascal, can you
> please tell me if I have done something wrong here?
> 
> // initialize all targets / target information
> LLVMInitializeAllTargets;
> LLVMInitializeAllTargetInfos;
> 
> // initialize native target in particular
> LLVMInitializeNativeTarget;
> 
> // get first target
> Target := LLVMGetFirstTarget;
> 
> // loop until the target is NULL
> while (Target <> nil) do
> begin
>   // get target name & description
>   TargetName := LLVMGetTargetName(Target);
>   TargetDescription := LLVMGetTargetDescription(Target);
> 
>   // do something with these information
> 
>   Target := LLVMGetNextTarget(Target);
> end;
> 
I don't see any obvious problems here, though someone else might.
What exactly is the problem you are seeing?  Is LLVMGetFirstTarget
returning NULL?

You may want to take a look at this code:
http://cgit.freedesktop.org/mesa/mesa/tree/src/gallium/drivers/radeon/radeon_llvm_emit.c
It is a pretty good example of using the C API for accessing the target
registry.  However, if you want to test this code directly, I would
recommend replacing the r600 target triple with your native
architecture, because the R600 backend is not built by default.

-Tom

> By debugging the LLVM library (a custom DLL, which works fine
> otherwise), I can see that there is no information, but I'm not that
> deep into C and the LLVM structure to identify what went wrong. Also I
> did a lot of tests the other day, trying several things without luck.
> 
> However, since I do not need this code at the moment, it's not urgent,
> just felt to let you know about my problems.
> 
> Kind regards,
> 
>     Christian
> 
> -- 
> Christian-W. Budde
> Eleonorenstr. 17
> 30449 Hannover
> Tel.: +49 511 31048857
> E-Mail: Christian at savioursofsoul.de
> WWW: http://www.savioursofsoul.de/Christian
> 
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

Am 13.05.2013 16:16, schrieb Tom Stellard:
> On Sat, May 11, 2013 at 01:48:44PM +0200, Christian Budde wrote:
>> Hello,
>>
>> a few days ago, I was trying to access the LLVM target registry via the
>> LLVM-C interface. Unfortunately I can't seem to get some useful
>> information out of it.
>>
>> Despite the fact that the following code is written in Pascal, can you
>> please tell me if I have done something wrong here?
>>
>> // initialize all targets / target information
>> LLVMInitializeAllTargets;
>> LLVMInitializeAllTargetInfos;
>>
>> // initialize native target in particular
>> LLVMInitializeNativeTarget;
>>
>> // get first target
>> Target := LLVMGetFirstTarget;
>>
>> // loop until the target is NULL
>> while (Target <> nil) do
>> begin
>>   // get target name & description
>>   TargetName := LLVMGetTargetName(Target);
>>   TargetDescription := LLVMGetTargetDescription(Target);
>>
>>   // do something with these information
>>
>>   Target := LLVMGetNextTarget(Target);
>> end;
>>
> I don't see any obvious problems here, though someone else might.
> What exactly is the problem you are seeing?  Is LLVMGetFirstTarget
> returning NULL?
LLVMGetFirstTarget returns a pointer at a quite high address. Subsequent
calls to LLVMGetNextTarget all return the very same pointer (much
lower). If I query LLVMGetTargetName and LLVMGetTargetDescription I got
an empty string and a null pointer.
> You may want to take a look at this code:
>
http://cgit.freedesktop.org/mesa/mesa/tree/src/gallium/drivers/radeon/radeon_llvm_emit.c
> It is a pretty good example of using the C API for accessing the target
> registry.  However, if you want to test this code directly, I would
> recommend replacing the r600 target triple with your native
> architecture, because the R600 backend is not built by default.
I've done it exactly like in this example (except the fact that I'm
using pascal as language and x86 as main target). So if the sequence of
calls seems to be right, I'll be investigating whether I've done
something wrong compiling the DLL.

Thanks for the information,

    Christian

-- 
Christian-W. Budde
Eleonorenstr. 17
30449 Hannover
Tel.: +49 511 31048857
E-Mail: Christian at savioursofsoul.de
WWW: http://www.savioursofsoul.de/Christian