similar to: RFC: A new ABI for virtual calls, and a change to the virtual call representation in the IR

Using relative offsets applies to more than just vtables. It would do wonders for constant strings too. -- Sean Silva On Mon, Feb 29, 2016 at 1:53 PM, Peter Collingbourne via cfe-dev < cfe-dev at lists.llvm.org> wrote: > Hi all, > > I'd like to make a proposal to implement the new vtable ABI described in > PR26723, which I'll call the relative ABI. That bug gives more

On Fri, Mar 4, 2016 at 2:48 PM, Peter Collingbourne <peter at pcc.me.uk> wrote: > On Mon, Feb 29, 2016 at 1:53 PM, <> wrote: >> >> @A_vtable = {i8*, i8*, i32, i32} {0, @A::rtti, @A::f - (@A_vtable + 16), >> @A::g - (@A_vtable + 16)} >> > > There's a subtlety about this aspect of the ABI that I should call > attention to. The virtual function

Please send any comments. As mentioned at the end I will follow up with some patches as soon as they are cleaned up and I create some test cases. RFC: Safe Whole Program Devirtualization Enablement =================================================== High Level Summary ------------------ The goal of the changes described in this RFC is to support aggressive Whole Program Devirtualization without

Mike Stump wrote: > On Mar 24, 2009, at 10:22 AM, Luke Dalessandro wrote: > >> I guess that alias analysis doesn't always "trust" casts, where if I >> manually >> pushed back I would be assuming that the casts are correct? > > Once all the pushing is in, one should be able to discover that the > casts all convert to the same type, and remove

Hi all, I'd like to make the following proposal to implement an optimization called virtual constant propagation. ==Introduction== After enabling control flow integrity protection in Chromium, we have observed an unacceptable performance regression in certain critical layout microbenchmarks. Profiling [0] revealed that the cause of the regression was a large number of virtual calls, each

> On Mar 4, 2016, at 2:48 PM, Peter Collingbourne via llvm-dev <llvm-dev at lists.llvm.org> wrote: > On Mon, Feb 29, 2016 at 1:53 PM, < <mailto:>> wrote: > @A_vtable = {i8*, i8*, i32, i32} {0, @A::rtti, @A::f - (@A_vtable + 16), @A::g - (@A_vtable + 16)} > > There's a subtlety about this aspect of the ABI that I should call attention to. The virtual function

The proposed mitigation for variant 2 of CVE-2017-5715, “branch target injection”, is to send all indirect branches through an instruction sequence known as a retpoline. Because the purpose of a retpoline is to prevent attacker-controlled speculation, we also end up losing the benefits of benign speculation, which can lead to a measurable loss of performance. We can regain some of those benefits

Wouldn't a branch funnel open the door to a type 1 attack? E.g. if the code looks like this, then a branch funnel basically turns into a standard type 1 pattern AFAICT: struct Base { virtual int f(long) = 0; }; struct A : Base { int f(long x) override { return 0; }; }; struct B : Base { int f(long x) override { // As in listing 1 in

Hi, Sean Silva via llvm-dev wrote: > Wouldn't a branch funnel open the door to a type 1 attack? Only if the code looks exactly as you wrote it. If I understand this correctly the problem with indirect branches is that the "gadget", the code leaking the data, could be *anywhere* in the binary, giving the attacker much more freedom. So restricting these calls to one of the

Hi, I just thought about another use case: VTable compression. If you know that an entry in the Vtable is never used, just remove it! I’d hope we could even eliminate some unused virtual functions from the final binary. — Mehdi > On Jan 27, 2016, at 10:29 PM, Mehdi Amini via llvm-dev <llvm-dev at lists.llvm.org> wrote: > > Hi Peter, > > Pete (Cooper, CC'ed) had a

I get some failing tests from compiler-rt. FAIL: cfi :: cross-dso/stats.cpp (30831 of 30893) ******************** TEST 'cfi :: cross-dso/stats.cpp' FAILED ******************** Script: -- /usr/local/google/home/prazek/llvm-build-release/./bin/clang -fuse-ld=gold -flto -fsanitize=cfi -fwhole-program-vtables --driver-mode=g++ -fsanitize-cfi-cross-dso -fvisibility=default -DSHARED_LIB -fPIC

There seem to be some recent regressions in clang/llvm. I see some test failing, and there is also this issue: https://llvm.org/bugs/show_bug.cgi?id=30466 Is anyone working on it? Piotr -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20160920/ade5e8cd/attachment.html>

<font face="Verdana,Arial,Helvetica,sans-serif" size="2"> <span><div>Hi,<br>There was a mention of optimizing away C++ dynamic_casts in LTO in this presentation: <a href="https://www.youtube.com/watch?v=Fd3afoM3UOE&t=1306" target="_blank">https://www.youtube.com/watch?v=Fd3afoM3UOE&t=1306</a><br>I

Hi all, I would like to propose a mechanism that allows IR modules to co-operatively build a pointer set corresponding to addresses within a given set of globals. The specific use case I have in mind is to provide a mechanism for a C++ program to efficiently verify (at each call site) that a vtable pointer is in the set of valid vtable pointers for the class or its derived classes. One way of

Dear Mailing List, This might sound unconventional, but I am trying to access a C++ objects vtable to pass as an argument to a function call for a library function I created. Creating & inserting a function call at the correct location in LLVM is done. I have learned that C++ objects are represented as struct types. But I'm just not quite sure how to get at the vtable pointer within,

Hi all, I wanted to make this proposal to extend ThinLTO to allow a bitcode module to embed another bitcode module containing summary information. The purpose of doing so is to support CFI and whole-program devirtualization optimizations under ThinLTO. Overview The CFI and whole-program devirtualization optimizations work by transforming vtables according to the class hierarchy. For example,

I would start from using module-level metadata. An IR extension might be a good idea once we show that - the proposed indirect call protection mechanism is efficient and useful, and - there are other use cases for the IR extension. --kcc On Wed, Jan 28, 2015 at 2:57 AM, Sean Silva <chisophugis at gmail.com> wrote: > Is there any way to accomplish this that doesn't require

I’ve almost finished a patch to add back in either out of line destructors or anchor methods. We seem to use one or the one, relatively inconsistently. What i’ve gone for is that if a class already had an inline destructor then i left it alone and added an anchor method. Otherwise I added an out of line destructor. Now if I compile Instructions.cpp with -Wweak-vtable, the only warnings given

Hello, In an effort to help LLVM-style projects save memory, I’ve been toying with some macros that provide an alternative to C++ vtables that use LLVM-style RTTI design patterns instead. Is this something that LLVM or sub-projects think is worth pursuing? Or are the macros below too ugly/problematic? Feedback would be appreciated. Thanks, Dave //===- llvm/Support/VTable.h - LLVM-style

So, bitset would be a property that means : globals with the same name will append on a string of bits in the order in which they appear, and it's the job of the front end to make sure the correct order is followed in every unit, so that linking does the right job in every corner case? Could that be used for efficient global boolean flags, like LLVM's options? Even if you don't need