llvm dev - Aug 2007 - [LLVMdev] Adding custom operation intrinsic for ASIP architectures.

Chris Lattner wrote:
> On Tue, 31 Jul 2007, [ISO-8859-1] Mikael Lepist� wrote:
>> I was talking with aKor in #llvm how we could implement custom
operation
>> support for our ASIP architecture. We came into solution that the best
>> way would be to write new custom operation intrinsic and optimization
>> pass for raising certain type of function calls to those intrinsics
>> (similar to raising mallocs).
>>
>> Basically our custom operation are like calls, with operand name and
>> multiple inputs and outputs. e.g. C code:
>> __llvm__custom_op_add(a,b,c) would be raised to customop add(i32 %tmp1,
>> i32 %tmp24 , i32 %tmp25). Those "__llvm__custom_op_" prefixed
function
>> will not have function body, but pure declarations in C code level.
>>
>> Comments are welcome, especially if there anyone else, that needs this
>> kind of functionality or if people has already implemented something
>> similar.
>
> Sure, this works. This is exactly the idea of the builtin functions in 
> GCC. For example, in SSE, the __builtin_ia32_movntps function does a 
> nontemporal store.
>
> To answer David's question, we already have direct support for this in 
> tblgen, for example, include/llvm/IntrinsicsX86.td contains:
>
> let TargetPrefix = "x86" in { // All intrinsics start with
"llvm.x86.".
> def int_x86_sse_movnt_ps :
GCCBuiltin<"__builtin_ia32_movntps">,
> Intrinsic<[llvm_void_ty, llvm_ptr_ty,
> llvm_v4f32_ty], [IntrWriteMem]>;
> }
>
> and lib/Target/X86/X86InstrSSE.td contains:
>
> def MOVNTPSmr : PSI<0x2B, MRMDestMem, (outs), (ins i128mem:$dst, 
> VR128:$src),
> "movntps {$src, $dst|$dst, $src}",
> [(int_x86_sse_movnt_ps addr:$dst, VR128:$src)]>;
>
> There is corresponding code in llvm-gcc to tell GCC how to handle this 
> builtin. Is this what you're looking for?
>
Yes this is more or less, what we are looking for, except we need 
variable arguments for out intrinsic. I assume that it can be achieved 
by using llvm_vararg_ty as a argument type?

Is there need to make changes to llvm-gcc for supporting new GCCBuiltin 
types that I define or are all of them automatically converted to 
intrinsics on gcc side?

Mikael Lepistö

On Wed, 1 Aug 2007, [UTF-8] Mikael Lepist? wrote:
>> def MOVNTPSmr : PSI<0x2B, MRMDestMem, (outs), (ins i128mem:$dst, 
>> VR128:$src),
>> "movntps {$src, $dst|$dst, $src}",
>> [(int_x86_sse_movnt_ps addr:$dst, VR128:$src)]>;
>>
>> There is corresponding code in llvm-gcc to tell GCC how to handle this 
>> builtin. Is this what you're looking for?
>>
>Yes this is more or less, what we are looking for, except we need 
>variable arguments for out intrinsic. I assume that it can be achieved 
>by using llvm_vararg_ty as a argument type?
Sure, that can be done.  What sort of operations require variable 
arguments?  It might be better implemented with pattern matching in the 
code generator than as an intrinsic.
> Is there need to make changes to llvm-gcc for supporting new GCCBuiltin 
> types that I define or are all of them automatically converted to 
> intrinsics on gcc side?
No, unfortunately you also have to use the GCC builtin mechanism to teach 
gcc about them.

-Chris

-- 
http://nondot.org/sabre/
http://llvm.org/

Chris Lattner wrote:
> On Wed, 1 Aug 2007, [UTF-8] Mikael Lepist? wrote:
>   
>>> def MOVNTPSmr : PSI<0x2B, MRMDestMem, (outs), (ins i128mem:$dst,
>>> VR128:$src),
>>> "movntps {$src, $dst|$dst, $src}",
>>> [(int_x86_sse_movnt_ps addr:$dst, VR128:$src)]>;
>>>
>>> There is corresponding code in llvm-gcc to tell GCC how to handle
this
>>> builtin. Is this what you're looking for?
>>>
>>>       
>> Yes this is more or less, what we are looking for, except we need 
>> variable arguments for out intrinsic. I assume that it can be achieved 
>> by using llvm_vararg_ty as a argument type?
>>     
>
> Sure, that can be done.  What sort of operations require variable 
> arguments?  It might be better implemented with pattern matching in the 
> code generator than as an intrinsic.
>   
Need for variable arguments is that we don't know beforehand
which custom operations we support. So practically we just
give operation name and 1 or more parameters depending
how many parameters custom operation has.

e.g. __custom_operation("addsub", a, b, c)

In lowering of intrinsic function we check from the processor,
which type of parameters our current processor has for operation
named "addsub" and write corresponding native
code.
>> Is there need to make changes to llvm-gcc for supporting new GCCBuiltin
>> types that I define or are all of them automatically converted to 
>> intrinsics on gcc side?
>>     
>
> No, unfortunately you also have to use the GCC builtin mechanism to teach 
> gcc about them.
>   
I already made optimizer pass for transforming certain function name
to intrinsic function. For me it seemed to be a lot easier choice.

Mikael Lepistö