[LLVMdev] strange code behavior when non-prototyped user function are called

[Duncan Sands]

Hi Chuck,

> However, if I comment out the first 2 lines (the prototype declarations),
> llvm-gcc will generate the following code for foo() instead:
> define void @foo() nounwind {
> entry:
> %0 = call i32 (...)* bitcast (void ()* @bar to i32 (...)*)() nounwind ; <i32>
> [#uses=0]

in C a prototype like this
   void bar()
or no prototype at all means that bar takes a variable number of arguments
(corresponds to ... in the LLVM type); if there is no prototype then bar
is also considered to return i32.

So in foo, the call to bar is technically a call to a function of type i32
(...).  However later the body of bar is output, at which point the type of
@bar is corrected to void (void).  This results in a bitcast in the call.
The instcombine pass should clean this up.

Ciao,

Duncan.