[LLVMdev] bitcast function calls

[Chris Lattner]

On Wed, 7 May 2008, Ben Mayne wrote:

> We are seeing some behavior we don't understand.  Some of our functions 
> are not showing up in the Call Graph because their calls contain 
> bitcasts.  The Call Graph then considers them to be external nodes. 
> The calls look as follows:
>
> %tmp35 = call i32 (...)* bitcast (i32 (i32, i8*, i32*)* @convert to i32 
> (...)*)( i32 %tmp33, i8* %tmp34, i8* %tmp30 )  ; <i32> [#uses=1]
>
> After looking deeper, we noticed that the 'convert' function above did 
> not have a prototype in the actual c source code.  After adding a 
> prototype and running llvm-gcc again, the call no longer contained the 
> bitcast and looked like any other normal call.
>
> This may be more related to gcc, but we're wondering why the initial 
> call to a function without a prototype contained a bitcast while a 
> function with a prototype does not.  We can go into the code and add 
> prototypes and get around the problem, but we'd like to better 
> understand what's going on to see if a better solution exists.

The instcombine pass fixes this.

-Chris

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