[llvm-dev] LLVM 3.9 RC2's SCCP pass removing calls to external functions?!

[Félix Cloutier via llvm-dev]

Hi,

I've been porting a project to LLVM 3.9 and found that the SCCP pass may remove calls to external functions if their return type is declared to be an empty struct. For instance:

> %empty = type {}
> 
> declare %empty @foo()
> 
> define i32 @main() {
>   %1 = call %empty @foo()
>   ret i32 0
> }


opt -sccp -S file.ll returns:

> %empty = type {}
> 
> declare %empty @foo()
> 
> define i32 @main() {
>   ret i32 0
> }


It doesn't look right to remove a call to an external function (especially since the call isn't removed if `@foo` returns a `void` instead). It didn't happen with LLVM 3.8.

I'm using the Mac OS X prebuilt binaries for RC2.

Assuming that this is a bug, what are the next steps?

Félix

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