[PATCH] D141836: [AArch64] Disable __muloti4 libcalls for AArch64

[Eric Christopher via llvm-commits]

The right move here is to check about muloti, not disable it unless the
aarch64 backend doesn't need it.

On Mon, Jan 23, 2023, 10:11 AM Renato Golin via Phabricator <
reviews at reviews.llvm.org> wrote:

> rengolin added a subscriber: echristo.
> rengolin added a comment.
>
> In D141836#4073296 <https://reviews.llvm.org/D141836#4073296>,
> @sebastianpoeplau wrote:
>
> >> From reading the thread on
> https://github.com/llvm/llvm-project/issues/16778 (which is closed,
> although the issue doesn't seem resolved), this is a stop-gap for
> toolchains that don't include an implementation for `__muloti4`. An
> implementation seems to exist in compiler-rt, but compiler-rt isn't linked
> with by default. It seems unfortunate that there is no way to still emit a
> call to `__muloti4` when we do link with compiler-rt, but from reading that
> thread there is currently no way to tell LLVM that an implementation of
> `__muloti4` is available.
> >
> > That's my understanding as well.
>
> Every few years I come to this issue via bugs or reviews. I am shocked
> that this is still an issue today...
>
> This isn't by far a good solution, but it will work around the "original"
> problem, just not the "actual" problem.
>
> I don't mind this going in as is, but I'll let @nickdesaulniers approve to
> be sure I'm not missing anything.
>
> @echristo FYI
>
>
>
> ================
> Comment at: llvm/lib/Target/AArch64/AArch64ISelLowering.cpp:607
> +  // The MULO libcall is not part of libgcc, only compiler-rt.
> +  setLibcallName(RTLIB::MULO_I128, nullptr);
> +
> ----------------
> please, add a comment:
> ```
> // TODO: Link compiler-rt's builtins by default in Clang once and for all
> // See: https://github.com/llvm/llvm-project/issues/16778
> ```
>
>
> Repository:
>   rG LLVM Github Monorepo
>
> CHANGES SINCE LAST ACTION
>   https://reviews.llvm.org/D141836/new/
>
> https://reviews.llvm.org/D141836
>
>
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