similar to: [LLVMdev] EHABI: Remaining issues

On 15 March 2014 17:06, Logan Chien <tzuhsiang.chien at gmail.com> wrote: > I would like to know what do you mean by "commoning them up"? Hi Logan, That'd be reducing ARM directives in favour of CFI, but as I said (and you too), GNU compatibility will probably be an issue for a very long time. > For the space issue, I personally don't think this is a big issue.

Folks, I'm sorry for getting at this again, but this will not be the last discussion on the topic, so let's just get to business. We're about to merge the last critical patch to make EHABI compatible with other EH mechanisms in LLVM (D3079), and that has unearthed a few issues with the function attributes. Logan's blog post [1] contains a proposal to split unwinding from

On 20 March 2014 02:09, Rafael Espíndola <rafael.espindola at gmail.com> wrote: > I think this is just 2. It uses .eh_frame for unwinding proper. The > only difference in .eh_frame is that there is a personality function > defined. If there is no debug information, it should still be possible to unwind the stack via the saved LR on the stack, no? If there is only line info, you

Folks, We're having some discussions about the behaviour of exception handling and Dwarf sharing unwind logic, tables, etc. and it seems that the code around it wasn't designed with any particular goal in mind, but evolved (like the EHABI) and now we're seeing the results from it. The problems below are assuming C vs. C++, but it actually apply to any possibly-exceptional vs.

On 6 February 2014 19:21, Richard Smith <richard at metafoo.co.uk> wrote: > > if (nounwind) > can't unwind > can't unwind == unwind table + no EH directives + no EH table if (uwtable || (!nounwind && need uwtable to unwind)) > unwind table > "need unwind table to unwind" is probably true in almost all cases. At least in all where

On 21 March 2014 18:47, Logan Chien <tzuhsiang.chien at gmail.com> wrote: > * There's the table for ARM target: > > - no attribute => emit unwind table > - with nounwind => emit unwind table with cantunwind > - with uwtable => emit unwind table > - with uwtable+nounwind => emit unwind table WITHOUT the cantunwind > > The cantunwind record will stop the

I'd love to hear more details. Are you saying that this infinite loop is a limitation of EHABI table format, and not something that can be fixed in the compiler? Meanwhile, please notice that gcc behavior matches current clang behavior that I described above. We would not want to create an incompatibility. On Fri, Feb 14, 2014 at 8:42 PM, Logan Chien <tzuhsiang.chien at gmail.com>

Dear all, AFAIK, ARM EHABI is not ready for both asm and obj emitter. Some people including me what to implement them. My question is, to avoid duplicate effort, does someone take charge of this part? or does anyone is already implementing this currently? BTW, any suggestion on this effort? I'm very appreciated! Thanks in advance! -- Best regards, Wen-Han Gu (Nowar) -------------- next

On Thu, Feb 13, 2014 at 5:52 PM, Renato Golin <renato.golin at linaro.org> wrote: > On 13 February 2014 13:47, Evgeniy Stepanov <eugenis at google.com> wrote: >> Hm, I see that -funwind-tables on arm-linux-androideabi target >> replaces this "cantunwind" with a proper unwind table. >> Hence http://llvm-reviews.chandlerc.com/D2762. > > If Android is

On 7 February 2014 00:19, Richard Smith <richard at metafoo.co.uk> wrote: > This (-fexceptions and -g imply -funwind-tables) seems like it's probably > the right thing for most targets. With SjLj exceptions, -fexceptions > probably doesn't need -funwind-tables. > Thanks, I think that's the general consensus, yes. Do we have such logic in Clang at the moment? My

> I disagree on this. Table emission by itself doesn't involve code > generation and I don't think it makes sense as a per function attribute > either. You either want it for all functions or only when needed (e.g. > exceptions are possible). As such, it makes perfect sense to me as a > global flag. It has to be an attribute because of LTO. You can LTO a file compiled with

Hello > My question is, to avoid duplicate effort, > does someone take charge of this part? or > does anyone is already implementing this currently? > > BTW, any suggestion on this effort? I'm very appreciated! There are several directions here: 1. Binary emission. Right now MC layer is text-only and depends on assembler 2. Correctness issues. It's believed that unwinding

Dear Renato and Anton, Big thanks to your help. Those references are very helpful! BTW, After I applying this patch from Logan Chien, I pass some examples on ARM assembly emission. It seems good to me. http://llvm.org/bugs/show_bug.cgi?id=7187#attach_9161 For object file emission, The first thing is making MC generate correct .ARM.exidx and .ARM.extab. I will keep tracing that. Thanks!

Hi all, I remember the discussion about promoting the integrated ARM assembler as the default option, but I don't remember the outcome. While compiling on ARM, I noticed that clang is not setting the integrated-as by default and is calling GAS before LD, which sometimes cause confusion (GAS doesn't like using r13 as a GPR, for instance). While this is unpredictable in Thumb, it's

Hi Renato, > is there anything holding the integrated assembler back from being on by default? For ARM-ELF, a couple missing pieces I see: 1) The assembly parser does not parse the ARM-ELF directives. 2) The Exception Handling ABI does not appear to be supported. Try this: $ echo "void a(){}" | clang -target arm-none-linux-gnueabi -mllvm -arm-enable-ehabi -integrated-as -c -xc -

On 10 February 2014 03:44, Renato Golin <renato.golin at linaro.org> wrote: > On 10 February 2014 02:59, Rafael Espíndola <rafael.espindola at gmail.com> wrote: >> It has to be an attribute because of LTO. You can LTO a file compiled >> with -fasynchronous-unwind-tables and one with >> -fno-asynchronous-unwind-tables. That is why we have the uwtable >>

Hi Francis, Thanks for getting back to me. Could you please provide more details about the problems you encounter with those tools and what improvements required to improve compact unwinding format? Most of my experience is in the mid end, but it is still surprising to me that an improved shrink wrap will break that many tools, considering the fact that gcc has a good shrink wrapping pass and

Hi, :If I compile this file with debugging enabled (clang/LLVM TOT) int main() { } I get the error Error: inconsistent uses of .cfi_sections From the 2.27 binutils assemblers. It seems that 2.27 doesn't like the .cfi_sections .debug_frame directive following previous .cfi directives. The assemblers seem to be happy if the .cfi_sections directive precedes any other .cfi directive. Is

> From: Tim Northover via llvm-dev <llvm-dev at lists.llvm.org> > Emitting directives in the epilogue is hard because the directives > apply to all instructions after in program-counter order. So if you > have an epilogue in the middle of a function and emit CFI directives > saying the registers are back where they were then the unwinder will > think that applies to the

Hello Everyone, This is my first attempt to getting used with the submission process. Trying to get the "good practice" with the coding standard, tools, mailing lists... and already a few questions: - Is it possible to "link" 2 related entries in Phabricator ? one for LLVM and one for CFE ? what's the best way of posting 2 related or dependent patches ? - I'd