similar to: [LLVMdev] isa and friends as an alternative to dynamic cast?

Evan, In case it wasn't obvious from Misha's answer, the main reason for doing this is speed. RTTI is not very quick. Since LLVM is well contained, there are no IR classes that LLVM doesn't know about it. Using dynamic_cast is really only warranted when blending libraries together that have inheritance relationships between them that aren't known in one or more of the libraries.

On Thu, 2005-21-04 at 19:43 -0700, Reid Spencer wrote: > In case it wasn't obvious from Misha's answer, the main reason for > doing this is speed. RTTI is not very quick. Right. This is why I was somewhat suprized to see the "isa" facilities included in LLVM without also disabling rtti. It will reduce the memory footprint a fair bit if you do disable it, at least based on

> It won't cause a negative effect, go for it! Dynamic_cast is realllly slow compared to dyn_cast, it is worth the memory. Ok, here's the first batch. It converts the RecTy hierarchy over to use LLVM-style RTTI. Along the way, I also wrote up a new doc "How to set up LLVM-style RTTI for your class hierarchy", which covers the previously undocumented (albeit not that

On Thu, 21 Apr 2005, Jeff Cohen wrote: > That's a good point. I think there are some issues with doing this (e.g. EH doesn't work, so the very few places we use it would have to be modified), but other than that I fully support the idea. -Chris > Evan Jones wrote: > >> On Thu, 2005-21-04 at 19:43 -0700, Reid Spencer wrote: >> >>> In case it wasn't

On Oct 4, 2012, at 5:15 PM, Sean Silva <silvas at purdue.edu> wrote: >> It won't cause a negative effect, go for it! Dynamic_cast is realllly slow compared to dyn_cast, it is worth the memory. > > Ok, here's the first batch. It converts the RecTy hierarchy over to > use LLVM-style RTTI. Along the way, I also wrote up a new doc "How to > set up LLVM-style

As far as I can tell, exceptions work just fine without RTTI when using gcc 3.4.2. dynamic_cast, on the hand, crashes without RTTI (no compilation error or warning is generated). Jeff Cohen wrote: > This may be the case with GCC, but VC++ allows exception handling to > be enabled while RTTI is disabled. According to VC++ documentation, > RTTI is needed only to support

My understanding is that EH works fine without RTTI. However, we use typeid in LLVM in a few limited spots like lib/VMCore/Pass.cpp Reid. On Sat, 2005-04-23 at 20:12 -0700, Jeff Cohen wrote: > As far as I can tell, exceptions work just fine without RTTI when using > gcc 3.4.2. dynamic_cast, on the hand, crashes without RTTI (no > compilation error or warning is generated). > >

It won't cause a negative effect, go for it! Dynamic_cast is realllly slow compared to dyn_cast, it is worth the memory. -Chris On Oct 3, 2012, at 9:39 PM, Sean Silva <silvas at purdue.edu> wrote: > Thanks for the feedback! > >>> Does anybody have anything else they think should go into TGContext or >>> any other responsibilities it should have? Or any

Thanks for the feedback! >> Does anybody have anything else they think should go into TGContext or >> any other responsibilities it should have? Or any feedback about the >> idea in general? > > All memory allocations should go into its bump pointer, RecordKeeper should as well. Any other global state that exist should also. Sounds good. >> I'm also hoping

This may be the case with GCC, but VC++ allows exception handling to be enabled while RTTI is disabled. According to VC++ documentation, RTTI is needed only to support dynamic_cast, the typeid operator, and the type_info class. Chris Lattner wrote: > On Thu, 21 Apr 2005, Jeff Cohen wrote: > >> That's a good point. > > > I think there are some issues with doing this

On Nov 12, 2010, at 5:57 PM, Óscar Fuentes wrote: >> Could someone >> please explain why I should use dyn_cast instead of dynamic_cast? (I >> thought all classes have v-tables...) Thanks, > > For reducing executable size, LLVM builds with RTTI disabled where > possible. Right, but how does that relate to dyn_cast? I thought v-tables were present even when RTTI is not

That's a good point. Evan Jones wrote: >On Thu, 2005-21-04 at 19:43 -0700, Reid Spencer wrote: > > >>In case it wasn't obvious from Misha's answer, the main reason for >>doing this is speed. RTTI is not very quick. >> >> > >Right. This is why I was somewhat suprized to see the "isa" facilities >included in LLVM without also

> I see a bunch of definitions scattered throughout LLVM, and I could not > find good documentation on them. I don't understand why they exist when > LLVM is being compiled with RTTI enabled. It seems to me that: > > isa<T>(x) is a substitute for (dynamic_cast<T>(x) != NULL) Misha seems to have answered your question, but documentation is found here:

This [1] might worth reading, Malhar. [1] http://llvm.org/docs/HowToSetUpLLVMStyleRTTI.html 2017-06-10 4:12 GMT+08:00 Tim Northover via llvm-dev < llvm-dev at lists.llvm.org>: > On 9 June 2017 at 12:03, Jajoo, Malhar via llvm-dev > <llvm-dev at lists.llvm.org> wrote: > > Is there some way around this ( without suggesting a change to my entire > AST ) ? > > LLVM

Hi, I would like to use std::shared_ptr in my pass. However I'm facing a problem wrt RTTI. If I have a code like: std::shared_ptr<BaseClass> x(new DerivedClass()); ... std::shared_ptr<DerivedClass> p = std::dynamic_pointer_cast<DerivedClass>(x); It does not compile since the default RTTI infrastructure is not used by LLVM. Also, it's not clear to me if the

Hi, I was wondering if it was possible to create a Dummy Type by subclassing LLVM Type. I do not want to create a new type or even do much with this dummy type , all I need is a placeholder type until I generate IR. I want to use this approach as most of my AST is already configured to accept a Type* and not a DummyType* ( which is my own class ) I explored this a bit and did manage to

LLVM has a relatively large number of proprietary replacements for standard C++ functions and classes. One of these is dyn_cast to replace dynamic_cast. The two calls appear to be semantically equivalent; the only difference that I can see is that dyn_cast reportedly works on classes that have no v-table [1]. Could someone please explain why I should use dyn_cast instead of dynamic_cast?

Trevor Harmon <Trevor.W.Harmon at nasa.gov> writes: [snip] > Could someone > please explain why I should use dyn_cast instead of dynamic_cast? (I > thought all classes have v-tables...) Thanks, For reducing executable size, LLVM builds with RTTI disabled where possible.

Hello, I recently ran into an issue where I wanted to use dyn_cast with a Multiple Inheritance hierarchy. LLVM’s help page on RTTI claims that it can be done, and that Clang’s Decl and DeclContext implement it; however, when I try to use it I run into odd behavior. Here’s my sample code which doesn’t work: ``` struct Base { void *ptr; bool hasInfo; }; struct Info { int size; static

Hi everyone, I just had a question - I am aware that LLVM supports it's own form of RTTI ( using dyn_cast<>() ,etc) but I wish to use C++ RTTI currently. I have tried building with "cmake -G "Unix Makefiles" -LLVM_ENABLE_RTTI=ON" but that doesnt seem to remove the "fno-rtti" flag from llvm-config and I still get an error when I try using