search for: strengthen

Has anyone done any experiments with regards to type strengthening or weakening in the context of LLVM? For example, the GWT compiler does type strengthening - that is, if you are calling a method on an interface or abstract type, and the compiler determines through live variable analysis what the concrete type is, then it goes ahead and re-writes the type...

Talin wrote: > For example, the GWT compiler does type strengthening - that is, if you > are calling a method on an interface or abstract type, and the compiler > determines through live variable analysis what the concrete type is, > then it goes ahead and re-writes the type information to be the stronger > type. The advantage is that it may then...

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 acquires if it recognizes it > lost dependencies during optimizations. Just thinking

On Tue, Jun 30, 2020 at 09:47:30PM +0200, Marco Elver wrote: > On Tue, 30 Jun 2020 at 19:39, Will Deacon <will at kernel.org> 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 consequently allowing for harmful > >

On Tue, Jun 30, 2020 at 03:57:54PM -0700, Sami Tolvanen wrote: > On Tue, Jun 30, 2020 at 12:47 PM Marco Elver <elver at google.com> wrote: > > > > On Tue, 30 Jun 2020 at 19:39, Will Deacon <will at kernel.org> wrote: > > > > > > When building with LTO, there is an increased risk of the compiler > > > converting an address dependency headed by a

On Tue, Jun 30, 2020 at 09:25:03PM +0200, Arnd Bergmann wrote: > On Tue, Jun 30, 2020 at 7:39 PM Will Deacon <will at kernel.org> wrote: > > +#define __READ_ONCE(x) \ > > +({ \ > > + int atomic = 1; \

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 000000000000..515e360b01a1 > > --- /dev/null > > +++ b/arch/arm64/include/asm/rwonce.h > > @@ -0,0 +1,63 @@ > >

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 example, but it's an ongoing concern over on the LTO > >

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 and consequently allowing for harmful > > reordering by the CPU. > >

On Tue, Jun 30, 2020 at 7:39 PM Will Deacon <will at kernel.org> wrote: > +#define __READ_ONCE(x) \ > +({ \ > + int atomic = 1; \ > + union { __unqual_scalar_typeof(x) __val; char __c[1]; } __u; \ > +

On Tue, Jun 30, 2020 at 7:39 PM Will Deacon <will at kernel.org> wrote: > +#define __READ_ONCE(x) \ > +({ \ > + int atomic = 1; \ > + union { __unqual_scalar_typeof(x) __val; char __c[1]; } __u; \ > +

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_ONCE() definition with one that provides acquire semantics when building with LTO. Signed-off-by:

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_ONCE() definition with one that provides acquire semantics when building with LTO. Signed-off-by:

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 3:51 PM Paul E. McKenney <paulmck at kernel.org> wrote: > > On Tue, Jul 07,

I have the following code and data data.csv "","Goal","Frequency","Weight","Group" "1","Move",13,0.245283018867925,"Public" "2","Create",10,0.188679245283019,"Public" "3","Strengthen",30,0.566037735849057,"Public" "4","Move",6,0.6,"Board" "5","Create",0,0,"Board" "6","Strengthen",4,0.4,"Board" "7","Move",19,0.301587301587302,"Total" "8&quot...

...academic papers are written for financial gain: Lawrence Lessig said that congressional representatives rarely hear counterarguments to the garbage they get from corporate lobbyists. The Trans Pacific Partnership (TPP, and probably also the Transatlantic Trade and Investment Partnership) will strengthen the rights of corporations in this area. If you think that will limit the progress of science and the useful arts, as I do, I suggest you contact your elected representatives and tell them so -- if you are a citizen of a country with elected representatives. I think we should also ask the Ame...

...on to control dependence. I note SimplifyCFG indirectly handles some simple cases. It will speculate the contents of a basic block into a predecessor but this is insufficient for more complex structures. This probably cherry-picks the most common cases by frequency. Have their been prior attempts strengthen dead code elimination w.r.t. control flow? If so, any guidance on what went wrong? Thanks David -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20160127/d4dee7cb/attachment.html>

On Wed, 25 Mar 2009, Vikram S. Adve wrote: > We do have a static array bounds checking algorithm based on the Omega > integer programming library, but it is not hugely effective. I think > this can be strengthened a *lot*. I should add that I would be interested in helping with hooking a good decision procedure into LLVM. This will be useful far beyond array bounds check elimination. What is the current thinking? SMT solver? John

...op) Requires: perl(Compress::Bzip2) Can't find perl(compress::bzip2) anywhere. thansk in advance! Fred -- ---- Fred Smith -- fredex at fcshome.stoneham.ma.us ----------------------------- I can do all things through Christ who strengthens me. ------------------------------ Philippians 4:13 -------------------------------

...machine of this generation to ?do the same thing. We're 7 years after their first results, and we now have access to massive cloud-based behemoths for a discount. How much time would it resist? The idea of removing weak ciphers from a widely used piece of software is a good one - that way, you strengthen the whole ecosystem. Going the reverse path would simply make less informed people be the weak link of the Internet, putting possibly many more at risk. Best regards, -- Emmanuel Deloget