llvm dev - Jul 2009 - [LLVMdev] How to produce a "Intrinsic Function" call instruction?

Hi, all.
I have noticed that LLVM supports some Intrinsic Functions such as *"**
llvm.sadd.with.overflow"* described in
http://llvm.org/docs/LangRef.html#int_sadd_overflow. We can use these
functions and needn't define the function bodies.

For example, I can manually insert codes:

    * %res = call {i32, i1} @llvm.sadd.with.overflow.i32(i32 %a, i32 %b)
     %sum = extractvalue {i32, i1} %res, 0
     %obit = extractvalue {i32, i1} %res, 1
     br i1 %obit, label %overflow, label %normal*

into an assembly file, and it works OK.

And now, my question is "How to produce such a call instruction using the
LLVM classes?"

I have also noticed that LLVM provides some classes like
"*MemCpyInst"* to
wrap the "*llvm.memcpy"* Intrinsic. But other intrinsic functions such
as *"
**llvm.sadd.with.overflow"* I've mentioned above don't have the
corresponding classes. How to deal with it?

Anyone could help me? Thank you!
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20090730/3b6011a4/attachment.html>

You can use your module to get the function or if not available create the
function and use it like any other functions you may have. This how I do :

Function fun = 0;
if ((fun=module->getFunction("llvm.sadd.with.overflow"))==0) {
vector<Type*> fun_arguments;
fun_arguments.push_back(...); //depends on your type
fun_arguments.push_back(...); //depends on your type
FunctionType *fun_type = FunctionType::get(Type::VoidTy, fun_arguments,
false);
fun = llvm::Function::Create(fun_type, GlobalValue::ExternalLinkage,
"llvm.sadd.with.overflow", module);
}
// insert your call to fun here


Olivier.


On Thu, Jul 30, 2009 at 10:38 AM, 张超 <gausszhch at gmail.com> wrote:
> Hi, all.
> I have noticed that LLVM supports some Intrinsic Functions such as
*"**
> llvm.sadd.with.overflow"* described in
> http://llvm.org/docs/LangRef.html#int_sadd_overflow. We can use these
> functions and needn't define the function bodies.
>
> For example, I can manually insert codes:
>
>     * %res = call {i32, i1} @llvm.sadd.with.overflow.i32(i32 %a, i32 %b)
>      %sum = extractvalue {i32, i1} %res, 0
>      %obit = extractvalue {i32, i1} %res, 1
>      br i1 %obit, label %overflow, label %normal*
>
> into an assembly file, and it works OK.
>
> And now, my question is "How to produce such a call instruction using
the
> LLVM classes?"
>
> I have also noticed that LLVM provides some classes like
"*MemCpyInst"* to
> wrap the "*llvm.memcpy"* Intrinsic. But other intrinsic functions
such as
> *"**llvm.sadd.with.overflow"* I've mentioned above don't
have the
> corresponding classes. How to deal with it?
>
> Anyone could help me? Thank you!
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20090730/29ec6d41/attachment.html>

Hey,

?? wrote:
> I have also noticed that LLVM provides some classes like
> "/*MemCpyInst"*/ to wrap the "/*llvm.memcpy"*/
Intrinsic. But other
> intrinsic functions such as /*"*//*llvm.sadd.with.overflow"*/
I've
> mentioned above don't have the corresponding classes. How to deal with
it?
For special instruction set intrinsics like SSE, you can use
Intrinsic::getDeclaration() which returns an llvm::Function* :
Intrinsic::getDeclaration(module, Intrinsic::sadd_with_overflow);

Have a look at include/llvm/Intrinsics.gen for the exact names.

Cheers,
Ralf