[LLVMdev] Upstreaming x32 ABI support

[Nadav Rotem]

Pavel, 

Thank you for writing to llvm-dev to describe your work on X32. It sounds like you are committed to making it happen and that other people in the community are also interested in this feature. When you send your patches to llvm-commit for review please CC people who could help with reviewing the patches. One way to find reviewers is to look at the 'svn blame’ line for areas of the code that you are modifying.

Thanks,
Nadav

> On Jul 2, 2014, at 7:59 AM, Pavel Chupin <pavel.v.chupin at gmail.com> wrote:
> 
> Hi all,
> 
> We (Intel) would like to revive this thread on X32 ABI support
> upstreaming. X32 ABI homepage is here:
> https://sites.google.com/site/x32abi/
> 
> Currently x32 support is available in kernel/glibc/gcc/binutils and
> one can install for example Ubuntu 14 with extra x32 lib packages
> (apt-get install libc6-dev-x32) to evaluate x32-target code generated
> by GCC (gcc supports x32 on Ubuntu 14 out of box).
> 
> We are planning to contribute enabling patches in LLVM/Clang trees and
> going to provide continuous support for this ABI in the future. Most
> of the changes obviously will be submitted to backend.
> 
> Our current work is based on:
> 
> * what’s currently done in trunk (some changes required for x32 are
> already there)
> * Michael Liao work done ~2 years ago and available here:
> http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20120604/058450.html
> 
> What’s currently in trunk:
> 
> * Triplet x86_64-*-linux-gnux32 (command line support, EnvironmentType
> enum to differentiate x32 from x86_64 by getTriple().getEnvironment()
> == llvm::Triple::GNUX32)
> https://github.com/llvm-mirror/llvm/commit/9dd2a3b1f2c253e20262535bb89b1ab6cc680ece
> * ILP32/LP64 differentiation for TargetMachine
> https://github.com/llvm-mirror/llvm/commit/a5597f0eaf1f93c6d0bc641a0cc54ecffb33955a
> * LEA tuning:
> https://github.com/llvm-mirror/llvm/commit/693c37aa86506be657dfaf8835845b0998531c3c
> * Bunch of tests (grep for gnux32):
> test/CodeGen/X86/imul64-lea.ll
> test/CodeGen/X86/stack-update-frame-opcode.ll
> test/CodeGen/X86/stack-update-frame-opcode.ll
> test/CodeGen/X86/x86-64-sret-return.ll
> test/CodeGen/X86/rip-rel-lea.ll
> test/CodeGen/X86/x86-64-sret-return-2.ll
> test/CodeGen/X86/x86-64-ptr-arg-simple.ll
> test/MC/X86/gnux32-dwarf-gen.s
> 
> What’s been done by Michael
> (http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20120604/058450.html)
> but not released in trunk:
> 
> * Clang Driver support (linker/libraries paths lookup, x32 specific
> flags, etc.). This change is rebased, modified and submitted here:
> http://reviews.llvm.org/D4180 . Welcome to review.
> * ELF support for x32. This change is rebased, modified and submitted
> here: http://reviews.llvm.org/D4181  . Welcome to review.
> * Use EBP/ESP as frame/stack pointer. This patch will be rebased
> modified and submitted soon.
> * Other cases which require introduction X32 specific instruction
> definitions such as JMPX32r/CALLX32r/CALLX32m.
> * X32 JIT support
> * I hope Michael correct me if I missed anything important
> 
> What’s still missing or experiencing issues (just something from the top):
> 
> * New tests required and several existing tests fail when extending to x32.
> * Pointer and struct return;
> * Cast int to pointer;
> * Function indirect calls;
> * TLS
> * Etc.
> 
> We don’t plan to introduce new backend from scratch. Major part of the
> changes are incremental to X86 backend and extend cases such as
> 
> (64bits) ? do-64 : do-32
> with
> (64bits) ? ((LP64) ? do-64 : do-x32) : do-32
> 
> or some shorter form if x32 mimic x86 or x86_64. X32 ABI is very close
> to x86-64 ABI.
> 
> Our plan is to start from basic stuff, focus on more tests adding and
> on stability issues, then continue with performance tuning. So the
> first 2 patches I submitted enable “Hello, world!” sample on Ubuntu
> 14. Patches are here:
> 
>                http://reviews.llvm.org/D4180
>                http://reviews.llvm.org/D4181
> 
> Next steps are to rebase and split Michael patch, cover with tests and
> submit by chunks convenient for review. Then move to other discovered
> issues.
> 
> Any suggestions and patches review are welcome!
> 
> -- 
> Pavel Chupin
> Intel Corporation
> 
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev