llvm dev - May 2008 - [LLVMdev] How to get a return type of a function with LLVM-C API

Hi LLVM-ers,

I am trying to get a return type of a function(from bitcode file) with
LLVM-C API, but there seems no appropriate API to do that.

I've tried to do that with following code,

----

LLVMModuleRef           M;
LLVMMemoryBufferRef     MemBuf;
LLVMValueRef            F;         // Function
LLVMTypeRef             RetTy;
char                   *ErrStr;

//
// -- Load shader module
//
ret = LLVMCreateMemoryBufferWithContentsOfFile(
         input,
        &MemBuf,    // [out]
        &ErrStr);   // [out]

ret = LLVMParseBitcode(
         MemBuf,
        &M,         // [out]
        &ErrStr);   // [out]

F = LLVMGetFirstFunction(M);

RetTy = LLVMGetReturnType(F);   // NG! Can't do this

----

How can I do that?
(I am using HEAD version of llvm)

And is there a tutorial or document for LLVM C API?


Thanks in advance.
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You're trying to apply an operation on a Type to a Value; that's no  
good, as you say. So you want the return type of the type of the  
function. But the function value itself is of type %function*, so you  
have to 'dereference' the type first:

LLVMGetReturnType(LLVMGetElementType(LLVMTypeOf(F)))

This may help to clarify:
http://llvm.org/docs/ProgrammersManual.html#coreclasses

On May 22, 2008, at 10:07, Syoyo Fujita wrote:
> Hi LLVM-ers,
>
> I am trying to get a return type of a function(from bitcode file)  
> with LLVM-C API, but there seems no appropriate API to do that.
>
> I've tried to do that with following code,
>
> ----
>
> LLVMModuleRef           M;
> LLVMMemoryBufferRef     MemBuf;
> LLVMValueRef            F;         // Function
> LLVMTypeRef             RetTy;
> char                   *ErrStr;
>
> //
> // -- Load shader module
> //
> ret = LLVMCreateMemoryBufferWithContentsOfFile(
>          input,
>         &MemBuf,    // [out]
>         &ErrStr);   // [out]
>
> ret = LLVMParseBitcode(
>          MemBuf,
>         &M,         // [out]
>         &ErrStr);   // [out]
>
> F = LLVMGetFirstFunction(M);
>
> RetTy = LLVMGetReturnType(F);   // NG! Can't do this
>
> ----
>
> How can I do that?
> (I am using HEAD version of llvm)
>
> And is there a tutorial or document for LLVM C API?
>
>
> Thanks in advance. _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev


— Gordon

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Hi Syoyo,
> I am trying to get a return type of a function(from bitcode file) with
> LLVM-C API, but there seems no appropriate API to do that.
From my memory, this info is stored in the function type, so you could look at
the function's type and get the info there.

Looking the the API docs [1], I find that there is a simple method on Function
called getReturnType(). You should thus be able to do:
	Type* rt = F->getReturnType();

Good luck,

Matthijs

[1]: http://llvm.org/doxygen/classllvm_1_1Function.html
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Hi Gordon and Matthjis,

I got the return type of the function in success with the way Gordon
explained.

RetTy = LLVMGetReturnType(LLVMGetElementType(LLVMTypeOf(F)))
Thanks a lot!

--
Syoyo


On Thu, May 22, 2008 at 11:33 PM, Gordon Henriksen <gordonhenriksen at
mac.com>
> wrote:
> You're trying to apply an operation on a Type to a Value; that's no
good,
> as you say. So you want the return type of the *type of the function*. But
> the function value itself is of type %function*, so you have to
> 'dereference' the type first:
>
> LLVMGetReturnType(LLVMGetElementType(LLVMTypeOf(F)))
>
> This may help to clarify:
> http://llvm.org/docs/ProgrammersManual.html#coreclasses
>




On Fri, May 23, 2008 at 12:02 AM, Matthijs Kooijman <matthijs at stdin.nl>
wrote:
> Hi Syoyo,
>
> > I am trying to get a return type of a function(from bitcode file) with
> > LLVM-C API, but there seems no appropriate API to do that.
> From my memory, this info is stored in the function type, so you could look
> at
> the function's type and get the info there.
>
> Looking the the API docs [1], I find that there is a simple method on
> Function
> called getReturnType(). You should thus be able to do:
>        Type* rt = F->getReturnType();
>
> Good luck,
>
> Matthijs
>
> [1]: http://llvm.org/doxygen/classllvm_1_1Function.html
>
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