Re: [PATCH] arm64: lse: fix LSE atomics with LLVM's integrated assembler
From: Ard Biesheuvel
Date: Tue Oct 08 2019 - 17:03:38 EST
On Tue, 8 Oct 2019 at 18:19, Robin Murphy <robin.murphy@xxxxxxx> wrote:
> On 08/10/2019 16:22, Sami Tolvanen wrote:
> > On Mon, Oct 7, 2019 at 2:46 PM 'Nick Desaulniers' via Clang Built
> > Linux <clang-built-linux@xxxxxxxxxxxxxxxx> wrote:
> >> I'm worried that one of these might lower to LSE atomics without
> >> ALTERNATIVE guards by blanketing all C code with `-march=armv8-a+lse`.
> > True, that's a valid concern. I think adding the directive to each
> > assembly block is the way forward then, assuming the maintainers are
> > fine with that.
> It's definitely a valid concern in principle, but in practice note that
> lse.h ends up included in ~99% of C files, so the extension is enabled
> more or less everywhere already.
lse.h currently does
which instructs the assembler to permit the use of LSE opcodes, but it
does not instruct the compiler to emit them, so this is not quite the