similar to: Proposal: virtual constant propagation

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

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

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

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

On Sat, Jan 31, 2015 at 11:35:01AM -0800, JF Bastien wrote: > Trying to summarize all opinions expressed here: Peter is proposing an > initial implementation that would only work with LTO. Folks seem put off by > this implementation affecting IR without having proven itself, and having > shortcomings (as Jim pointed out). Kostya proposed going through metadata > (and Chris kind of

There are two 64-bit bitmasks maintained in AttributeImpl.h<https://sdocc.itg.ti.com/ui#file:review=11893/version=393846>: - AvailableFunctionAttrs is part of the AttributeListImpl class, and - AvailableAttrs is part of the AttributeSetNode class Both of these assume that the number of available enum attributes is limited to 64. In fact, a static_assert in

On 29 Jan 2015 11:36, "Sean Silva" <chisophugis at gmail.com> wrote: > > > > On Thu, Jan 29, 2015 at 12:53 AM, Renato Golin <renato.golin at linaro.org> wrote: >> >> 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

Trying to summarize all opinions expressed here: Peter is proposing an initial implementation that would only work with LTO. Folks seem put off by this implementation affecting IR without having proven itself, and having shortcomings (as Jim pointed out). Kostya proposed going through metadata (and Chris kind of did too by mentioning tbaa), but Peter points out that this will make the

On Sat, Jan 31, 2015 at 2:07 PM, Peter Collingbourne <peter at pcc.me.uk> wrote: > On Sat, Jan 31, 2015 at 11:35:01AM -0800, JF Bastien wrote: > > Trying to summarize all opinions expressed here: Peter is proposing an > > initial implementation that would only work with LTO. Folks seem put off > by > > this implementation affecting IR without having proven itself,

On 2009-12-21 18:06, David Greene wrote: > On Saturday 19 December 2009 00:16, Chris Lattner wrote: > > >>> Or I think I can just assume (Yikes!) that if the signal handler is >>> invoked it will really be a circular_raw_ostream since the handler >>> should (!) only be set up in debug mode. >>> >>> That scares me a bit, though. >>>

Hi all, I'd like to add support for metadata attachments for global variables in the same way as we did for functions. Syntax would be pretty simple: @foo = global i32 0, !foo !0, !bar !1 (the extra commas are required to disambiguate from a named metadata on the next line) Benefits: 1) Lets us reverse the DIGlobalVariable -> GlobalVariable edge, which should hopefully clear the way for

On Thu, Jan 29, 2015 at 02:22:48PM -0800, Peter Collingbourne wrote: > I've been working on a patch that implements the bitset attribute and bitset > lowering pass. I'll see if I can send it out later today. http://reviews.llvm.org/D7288 Thanks, -- Peter

On Saturday 19 December 2009 00:16, Chris Lattner wrote: > > Or I think I can just assume (Yikes!) that if the signal handler is > > invoked it will really be a circular_raw_ostream since the handler > > should (!) only be set up in debug mode. > > > > That scares me a bit, though. > > Why don't you just check #ifndef NDEBUG like the code that sets it up?

Hi all, The bitset metadata currently used in LLVM has a few problems: 1. It has the wrong name. The name "bitset" refers to an implementation detail of one use of the metadata (i.e. its original use case, CFI). This makes it harder to understand, as the name makes no sense in the context of virtual call optimization. 2. It is represented using a global named metadata node, rather than

Hi Chris, I wanted to start by giving an explanation of what I am trying to achieve and how I am trying to achieve it. I am working towards introducing into LLVM a security mechanism, Forward Control Flow Integrity (CFI), that is designed to mitigate against vulnerabilities that allow attacks based on corrupting vtable or function pointers in memory in order to subvert a program's control

Hi, Daniel, thank you for your advice. Yes, ALL_MEMORY points to ALL_MEMORY. We use MD(memory descriptor) to abstract a memory location.  MD contains 4 main fields: id, base, offset, size. For these special MD (ALL_MEMORY, GLOBAL_MEMORY, STACK_MEMORY, HEAP_MEMORY),  we give them id 1, 2, 3, 4, that means MD1 is ALL_MEMORY, MD2 is GLOBAL_MEMORY, the same goes for the rest.  Then we maintain a

> On Jan 29, 2015, at 6:50 PM, Peter Collingbourne <peter at pcc.me.uk> wrote: > > On Thu, Jan 29, 2015 at 02:22:48PM -0800, Peter Collingbourne wrote: >> I've been working on a patch that implements the bitset attribute and bitset >> lowering pass. I'll see if I can send it out later today. > > http://reviews.llvm.org/D7288

On Thu, Mar 21, 2013 at 12:29 AM, Steven Su <steven_known at yahoo.com.cn> wrote: > Hi, Daniel, thank you for your advice. > Yes, ALL_MEMORY points to ALL_MEMORY. > > We use MD(memory descriptor) to abstract a memory location. > MD contains 4 main fields: id, base, offset, size. > For these special MD (ALL_MEMORY, GLOBAL_MEMORY, STACK_MEMORY, HEAP_MEMORY), > we give them

On Tue, Feb 03, 2015 at 04:03:45PM -0800, Sean Silva wrote: > One other thing: if this can be used for control-flow integrity, I assume > it has to have good knowledge of the available indirect call targets. Could > we also use this information for devirtualization? I would expect so. If a bitset contains only one element, we should be able to teach the lowering pass to simply test that

Hi all, I consider writing a R package on statistics for the sorting method as a hobby. I have written a private Java application that I could use as a basis. Therefore I'd like to ask two questions: 1) logical vectors: Bit storage (small) and capable of bit operations? The Java application relies on BitSet(s) for efficiency reasons. Arrays of logical values cost far too much memory (in the