On Tue, Jul 07, 2020 at 04:01:28PM -0700, Nick Desaulniers wrote:
> I'm trying to put together a Micro Conference for Linux Plumbers
> conference focused on "make LLVM slightly less shitty." Do you all
> plan on attending the conference? Would it be worthwhile to hold a
> session focused on discus
I'm trying to put together a Micro Conference for Linux Plumbers
conference focused on "make LLVM slightly less shitty." Do you all
plan on attending the conference? Would it be worthwhile to hold a
session focused on discussing this (LTO and memory models) be
worthwhile?
On Tue, Jul 7, 2020 at
On Mon, Jul 06, 2020 at 05:08:20PM +0100, Dave Martin wrote:
> On Tue, Jun 30, 2020 at 06:37:34PM +0100, Will Deacon wrote:
> > diff --git a/arch/arm64/include/asm/rwonce.h
> > b/arch/arm64/include/asm/rwonce.h
> > new file mode 100644
> > index ..515e360b01a1
> > --- /dev/null
> > +++
On Mon, Jul 06, 2020 at 05:00:23PM +0100, Dave Martin wrote:
> On Thu, Jul 02, 2020 at 08:23:02AM +0100, Will Deacon wrote:
> > On Wed, Jul 01, 2020 at 06:07:25PM +0100, Dave P Martin wrote:
> > > Also, can you illustrate code that can only be unsafe with Clang LTO?
> >
> > I don't have a concrete
On Wed, Jul 01, 2020 at 06:07:25PM +0100, Dave P Martin wrote:
> On Tue, Jun 30, 2020 at 06:37:34PM +0100, Will Deacon wrote:
> > When building with LTO, there is an increased risk of the compiler
> > converting an address dependency headed by a READ_ONCE() invocation
> > into a control dependency
On Wed, Jul 1, 2020 at 12:19 PM Will Deacon wrote:
> On Tue, Jun 30, 2020 at 09:25:03PM +0200, Arnd Bergmann wrote:
> > On Tue, Jun 30, 2020 at 7:39 PM Will Deacon wrote:
> > Once we make gcc-4.9 the minimum version,
> > this could be further improved to
> >
> >__auto_type __x = &(x);
>
>
On Tue, Jun 30, 2020 at 03:57:54PM -0700, Sami Tolvanen wrote:
> On Tue, Jun 30, 2020 at 12:47 PM Marco Elver wrote:
> >
> > On Tue, 30 Jun 2020 at 19:39, Will Deacon wrote:
> > >
> > > When building with LTO, there is an increased risk of the compiler
> > > converting an address dependency heade
On Tue, Jun 30, 2020 at 09:47:30PM +0200, Marco Elver wrote:
> On Tue, 30 Jun 2020 at 19:39, Will Deacon wrote:
> >
> > When building with LTO, there is an increased risk of the compiler
> > converting an address dependency headed by a READ_ONCE() invocation
> > into a control dependency and conse
On Tue, Jun 30, 2020 at 09:25:03PM +0200, Arnd Bergmann wrote:
> On Tue, Jun 30, 2020 at 7:39 PM Will Deacon wrote:
> > +#define __READ_ONCE(x) \
> > +({ \
> > + int atomic = 1
On Tue, Jun 30, 2020 at 09:47:30PM +0200, Marco Elver wrote:
> I do wonder, though, if there is some way to make the compiler do
> something better for us. Clearly, implementing real
> memory_order_consume hasn't worked out until today. But maybe the
> compiler could promote dependent loads to acqu
On Tue, Jun 30, 2020 at 7:39 PM Will Deacon wrote:
> +#define __READ_ONCE(x) \
> +({ \
> + int atomic = 1; \
> + union { _
When building with LTO, there is an increased risk of the compiler
converting an address dependency headed by a READ_ONCE() invocation
into a control dependency and consequently allowing for harmful
reordering by the CPU.
Ensure that such transformations are harmless by overriding the generic
READ
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