similar to: [LLD] RFC Range Thunks Implementation review for ARM and Mips

Are you suggesting other linker jobs such as creating _end symbols to the linker script? The linker script support was implemented after we wrote the current Writer class, so it is somewhat "plugged in" to the Writer. It might not be the best design, and not many other options have been explored. So there might be room to improve code by moving work loads from the Writer to the

On 6 April 2017 at 07:01, Peter Smith <peter.smith at linaro.org> wrote: > My understanding is that this would be (initially) limited to > fabricating enough linker script commands such that we could replace: > fixSectionAlignments() > assignAddresses() > Script->processNonSectionCommands() > > With something like: > Script->assignAddresses() // Could be done

I'm about to start working on range extension thunks in lld. This is an attempt to summarize the approach I'd like to take and what the impact will be on lld outside of thunks. I'm interested if anyone has any constraints the approach will break, alternative suggestions, or is working on something I'll need to take account of? I expect range extension thunks to be important for

Hello Rui, Thanks for the comments - Synthetic sections and rewriting relocations I think that this would definitely be worth trying. It should remove the need for thunks to be represented in the core data structures, and would allow . It would also mean that we wouldn't have to associate symbols with thunks as the relocations would directly target the thunks. ARM interworking makes reusing

Sure. One thing I want to remind you is that there is a place in Writer.cpp where we assume all synthetic sections were appended to end of Sections list. Look for `llvm::reverse`. If you add synthetic section thunks right before/after non-synthetic sections, you also want to change that. On Tue, Nov 29, 2016 at 1:18 PM, Simon Atanasyan <simon at atanasyan.com> wrote: > Hi, > >

Hi, Sorry for delay with reply. It looks like now thunks can be implemented as a synthetic sections. In that case we give flexible solution and will be able to put thunks before/after related sections, using different alignment etc. As far as I know BFD linker uses the same approach at least for MIPS thunks. I will try to implement this idea. On Thu, Sep 8, 2016 at 1:44 AM, Rui Ueyama <ruiu

After looking at this for a while, I do not think that this problem is NP-hard. With a finite "short branch" displacement k, I was not able to come up with a gadget that could create global constraints as would be needed to e.g. model an instance of 3SAT or vertex cover in terms of this problem. The problem is hard though. I believe that it is likely to be exponential in the "short

I've been working on supporting ARM/Thumb interworking thunks in LLD and have encountered a limitation that I think it is worth bringing up in a wider context. This is all LLD specific, apologies if I've abused llvm-dev here. TL;DR summary: - Thunks in lld may not work if they are added to InputSections that have already been scanned. - There is a short term fix, but in the longer term I

On Fri, Jan 6, 2017 at 6:21 AM, Rui Ueyama via llvm-dev < llvm-dev at lists.llvm.org> wrote: > On Thu, Jan 5, 2017 at 8:15 PM, Peter Smith <peter.smith at linaro.org> > wrote: > >> Hello Rui, >> >> Thanks for the comments >> >> - Synthetic sections and rewriting relocations >> I think that this would definitely be worth trying. It should

Hi, MIPS LA25 thunk is used to call PIC function from non-PIC code. Usually it contains three instructions: lui $25, %hi(func) addiu $25, $25, %lo(func) j func We can write such thunk in an arbitrary place of the generated file. But if a PIC function requires the thunk is the first routine in a section, we can optimize the code and escape jump instruction. To do so we just write the

On Wed, Oct 19, 2016 at 3:34 AM, Peter Smith via llvm-dev < llvm-dev at lists.llvm.org> wrote: > Thanks for the RFC. > > I'm in favour of the option of creating InputSections for some linker > generated content. I think it would add extra flexibility to the > linker. ARM's proprietary linker uses the equivalent of InputSections > with a pseudo linker defined

Zig tests using Debug build of 5.0.1rc2 hit this bug: https://bugs.llvm.org/show_bug.cgi?id=34452 I suppose the fix has not been backported to 5.0.1. So I created a Release build of 5.0.1rc2 and all zig tests pass, with the following patches: * Patches to LLD: commit a206ef34bbbc46017e471063a4a1832c1ddafb0a Author: Andrew Kelley <superjoe30 at gmail.com> Date: Fri Dec 1 12:11:55 2017

On Jan 19, 2017 2:48 AM, "Ed Maste" <emaste at freebsd.org> wrote: On 4 January 2017 at 13:34, Peter Smith via llvm-dev <llvm-dev at lists.llvm.org> wrote: > I'm about to start working on range extension thunks in lld. This is > an attempt to summarize the approach I'd like to take and what the > impact will be on lld outside of thunks. Now that LLD works

On 8 Oct 2014, at 18:19, Reid Kleckner <rnk at google.com> wrote: > The one target I know about where varargs are passed differently from normal arguments is aarch64-apple-ios/macosx. After thinking a bit more, I think this forwarding thunk representation works fine even on that target. Typically a forwarding thunk is called indirectly, or at least through a bitcast, so the LLVM IR call

First of all thanks for finding the bug. I agree with Rui that right now we can manage without general thunk infrastructure. Let's provide at least a few "thunk" implementation and after that reconsider necessity of common thunk framework. As to MIPS there is one more type of thunk (keyword is .MIPS.stubs) and one more optimization of current thunk (putting a thunk in the beginning

I needed this functionality to solve http://llvm.org/PR20653, but it obviously has far more general applications. You can do it like this: define i32 @my_forwarding_thunk(i32 %arg1, i8* %arg2, ...) { ... ; define new_arg1 and new_arg2 %r = musttail call i32 (i32, i8*, ...)* @the_true_target(i32 %new_arg1, i8* %new_arg2, ...) ret i32 %r } declare i32 @the_true_target(i32, i8*, ...) The

I would suggest converting only part of linker generated sections to input sections to reduce amount of code changes. For example it's unlikely that SymbolTableSection or StringTableSection would ever require such treatment, so why converting them to input sections? 2016-10-19 11:03 GMT+03:00 George Rimar <grimar at accesssoftek.com>: >>This idea popped up in the review thread

Hello Leslie, I don't know quite what to say as I don't know precisely what your question is? If I am not being precise enough please can you put some explicit questions in? From what I can see in the output, here are some comments. >From your arc mapfiles it looks like that in the output both linker's have given the .text output section the correct base address given the

Hello Leslie, The errors coming from the gnu assembler are due to the file being assembled in Arm state, to get rid of the errors you'll either need to put a .thumb directive in the file, or pass -mthumb to the assembler via arm-linux-gnu-gcc -Wa,-mthumb (I think). I'm not able to explain what you are seeing in your print out as it doesn't quite match the map file. Looking at your

On Fri, Feb 2, 2018 at 4:36 PM David Woodhouse <dwmw2 at infradead.org> wrote: > On Sat, 2018-02-03 at 00:23 +0000, Chandler Carruth wrote: > > > > Two aspects to this... > > > > One, we're somewhat reluctant to guarantee an ABI here. At least I > > am. While we don't *expect* rampant divergence here, I don't want > > this to become