[llvm-dev] [llvm][Linker] llvm-link / ModuleLinker drops GlobalIFuncs

[Fāng-ruì Sòng via llvm-dev]

On Wed, Aug 11, 2021 at 7:27 AM Itay Bookstein via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
>
> It appears that the code in llvm/lib/Linker/LinkModules.cpp doesn't
> take GlobalIFunc-s into account, and therefore drops them. There are
> three loops that iterate over GlobalVariable, Function and GlobalAlias
> respectively, to collect them into ValuesToLink. I'm wondering whether
> replacing these three loops with a single loop over all GlobalValues
> is sufficient to remedy this.
> WDYT?

Looks good.


% cat a.ll
@foo = dso_local ifunc i32 (...), bitcast (i8* ()* @foo_resolver to i32 (...)*)

; Function Attrs: noinline nounwind optnone uwtable
define dso_local i32 @foo_impl() #0 {
entry:
  ret i32 42
}

; Function Attrs: noinline nounwind optnone uwtable
define dso_local i8* @foo_resolver() #0 {
entry:
  ret i8* bitcast (i32 ()* @foo_impl to i8*)
}

attributes #0 = { "frame-pointer"="all" }
% llvm-link a.ll -S -o b.ll

The ifunc is incorrectly dropped.

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